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1

Quantum Field Theory & Gravity  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

Field Theory & Gravity Quantum Field Theory & Gravity Understanding discoveries at the Energy, Intensity, and Cosmic Frontiers Get Expertise Rajan Gupta (505) 667-7664 Email...

2

Quantum Field Theory in Graphene  

E-Print Network [OSTI]

This is a short non-technical introduction to applications of the Quantum Field Theory methods to graphene. We derive the Dirac model from the tight binding model and describe calculations of the polarization operator (conductivity). Later on, we use this quantity to describe the Quantum Hall Effect, light absorption by graphene, the Faraday effect, and the Casimir interaction.

I. V. Fialkovsky; D. V. Vassilevich

2011-11-13T23:59:59.000Z

3

Quantum computation of scattering in scalar quantum field theories  

Science Journals Connector (OSTI)

Quantum field theory provides the framework for the most fundamental physical theories to be confirmed experimentally and has enabled predictions of unprecedented precision. However, calculations of physical observables often require great computational ... Keywords: quantum algorithm, quantum field theory, simulation

Stephen P. Jordan, Keith S. M. Lee, John Preskill

2014-09-01T23:59:59.000Z

4

Indefinite-Metric Quantum Field Theory  

Science Journals Connector (OSTI)

......Umezawa H. Quantum Field Theory (1956) North Holland...Wightman L. Arch. Fysik (1964) 28:129. Y...indefinite-metric quantum field theory, which was published...book, except for some basic points. The use of the...space in quantum field theory has been motivated for......

Noboru Nakanishi

1972-03-01T23:59:59.000Z

5

Algebras without Involution and Quantum Field Theories  

E-Print Network [OSTI]

Explicit realizations of quantum field theory (QFT) are admitted by a revision to the Wightman axioms for the vacuum expectation values (VEV) of fields. The technical development of QFT is expanded beyond positive functionals on *-algebras while the physically motivated properties: Poincare covariance; positive energy; microcausality; and a Hilbert space realization of states, are preserved.

Glenn Eric Johnson

2014-10-01T23:59:59.000Z

6

Magnetic Charge and Quantum Field Theory  

Science Journals Connector (OSTI)

A quantum field theory of magnetic and electric charge is constructed. It is verified to be relativistically invariant in consequence of the charge quantization condition eg?c=n, an integer. This is more restrictive than Dirac's condition, which would also allow half-integral values.

Julian Schwinger

1966-04-29T23:59:59.000Z

7

From Quantum Mechanics to Quantum Field Theory: The Hopf route  

E-Print Network [OSTI]

From Quantum Mechanics to Quantum Field Theory: The Hopf route A. I. Solomon1 2, G. E. H. Duchamp3. Eliasza-Radzikowskiego 152, PL 31-342 Krak´ow, Poland E-mail: a.i.solomon@open.ac.uk, gduchamp2@free solvable model (at least in the free boson case). On the basis of a combinatorial methodology, we show

Paris-Sud XI, Université de

8

From Quantum Mechanics to Quantum Field Theory: The Hopf route  

E-Print Network [OSTI]

From Quantum Mechanics to Quantum Field Theory: The Hopf route A. I. Solomon 1 2 , G. E. H. Duchamp. Eliasza­Radzikowskiego 152, PL 31­342 Krak??ow, Poland E­mail: a.i.solomon@open.ac.uk, gduchamp2@free solvable model (at least in the free boson case). On the basis of a combinatorial methodology, we show

Recanati, Catherine

9

8.324 Quantum Field Theory II, Fall 2002  

E-Print Network [OSTI]

Second semester of a three-semester subject sequence on quantum field theory stressing the relativistic quantum field theories relevant to the physics of the Standard Model. Develops in depth some of the topics discussed ...

Hanany, Amihay

10

"Quantum Field Theory and QCD"  

SciTech Connect (OSTI)

This grant partially funded a meeting, "QFT & QCD: Past, Present and Future" held at Harvard University, Cambridge, MA on March 18-19, 2005. The participants ranged from senior scientists (including at least 9 Nobel Prize winners, and 1 Fields medalist) to graduate students and undergraduates. There were several hundred persons in attendance at each lecture. The lectures ranged from superlative reviews of past progress, lists of important, unsolved questions, to provocative hypotheses for future discovery. The project generated a great deal of interest on the internet, raising awareness and interest in the open questions of theoretical physics.

Jaffe, Arthur M.

2006-02-25T23:59:59.000Z

11

Nonlinear quantum equations: Classical field theory  

SciTech Connect (OSTI)

An exact classical field theory for nonlinear quantum equations is presented herein. It has been applied recently to a nonlinear Schrdinger equation, and it is shown herein to hold also for a nonlinear generalization of the Klein-Gordon equation. These generalizations were carried by introducing nonlinear terms, characterized by exponents depending on an index q, in such a way that the standard, linear equations, are recovered in the limit q? 1. The main characteristic of this field theory consists on the fact that besides the usual ?(x(vector sign),t), a new field ?(x(vector sign),t) needs to be introduced in the Lagrangian, as well. The field ?(x(vector sign),t), which is defined by means of an additional equation, becomes ?{sup *}(x(vector sign),t) only when q? 1. The solutions for the fields ?(x(vector sign),t) and ?(x(vector sign),t) are found herein, being expressed in terms of a q-plane wave; moreover, both field equations lead to the relation E{sup 2}=p{sup 2}c{sup 2}+m{sup 2}c{sup 4}, for all values of q. The fact that such a classical field theory works well for two very distinct nonlinear quantum equations, namely, the Schrdinger and Klein-Gordon ones, suggests that this procedure should be appropriate for a wider class nonlinear equations. It is shown that the standard global gauge invariance is broken as a consequence of the nonlinearity.

Rego-Monteiro, M. A.; Nobre, F. D. [Centro Brasileiro de Pesquisas Fsicas and National Institute of Science and Technology for Complex Systems, Rua Xavier Sigaud 150, 22290-180 Rio de Janeiro - RJ (Brazil)] [Centro Brasileiro de Pesquisas Fsicas and National Institute of Science and Technology for Complex Systems, Rua Xavier Sigaud 150, 22290-180 Rio de Janeiro - RJ (Brazil)

2013-10-15T23:59:59.000Z

12

Quantum field theory over F1  

E-Print Network [OSTI]

In this paper we discuss some questions about geometry over the field with one element, motivated by the properties of algebraic varieties that arise in perturbative quantum field theory. We follow the approach to F1-geometry based on torified schemes. We first discuss some simple necessary conditions in terms of Euler characteristic and classes in the Grothendieck ring, then we give a blowup formula for torified varieties and we show that the wonderful compactifications of the graph configuration spaces, that arise in the computation of Feynman integrals in position space, admit an F1-structure. By a similar argument we show that the moduli spaces of curves of genus zero with n marked points admit an F1-structure. We also discuss conditions on hyperplane arrangements, a possible notion of embedded F1-structure and its relation to Chern classes, and questions on Chern classes of varieties with regular torifications.

Dori Bejleri; Matilde Marcolli

2012-09-21T23:59:59.000Z

13

Causality Is Inconsistent With Quantum Field Theory  

SciTech Connect (OSTI)

Causality in quantum field theory means the vanishing of commutators for spacelike separated fields (VCSSF). I will show that VCSSF is not tenable. For VCSSF to be tenable, and therefore, to have both retarded and advanced propagators vanish in the elsewhere, a superposition of negative energy antiparticle and positive energy particle propagators, traveling forward in time, and a superposition of negative energy particle and positive energy antiparticle propagators, traveling backward in time, are required. Hence VCSSF predicts non-vanishing probabilities for both negative energy particles in the forward-through-time direction and positive energy antiparticles in the backwards-through-time direction. Therefore, since VCSSF is unrealizable in a stable universe, tachyonic propagation must occur in denial of causality.

Wolf, Fred Alan [Global Quantum Physics Educational Company, San Francisco CA (United States)

2011-11-29T23:59:59.000Z

14

Duality and Braiding in Twisted Quantum Field Theory  

E-Print Network [OSTI]

We re-examine various issues surrounding the definition of twisted quantum field theories on flat noncommutative spaces. We propose an interpretation based on nonlocal commutative field redefinitions which clarifies previously observed properties such as the formal equivalence of Green's functions in the noncommutative and commutative theories, causality, and the absence of UV/IR mixing. We use these fields to define the functional integral formulation of twisted quantum field theory. We exploit techniques from braided tensor algebra to argue that the twisted Fock space states of these free fields obey conventional statistics. We support our claims with a detailed analysis of the modifications induced in the presence of background magnetic fields, which induces additional twists by magnetic translation operators and alters the effective noncommutative geometry seen by the twisted quantum fields. When two such field theories are dual to one another, we demonstrate that only our braided physical states are covariant under the duality.

Mauro Riccardi; Richard J. Szabo

2007-11-09T23:59:59.000Z

15

Viscosity, Black Holes, and Quantum Field Theory  

E-Print Network [OSTI]

We review recent progress in applying the AdS/CFT correspondence to finite-temperature field theory. In particular, we show how the hydrodynamic behavior of field theory is reflected in the low-momentum limit of correlation functions computed through a real-time AdS/CFT prescription, which we formulate. We also show how the hydrodynamic modes in field theory correspond to the low-lying quasinormal modes of the AdS black p-brane metric. We provide a proof of the universality of the viscosity/entropy ratio within a class of theories with gravity duals and formulate a viscosity bound conjecture. Possible implications for real systems are mentioned.

D. T. Son; A. O. Starinets

2007-04-02T23:59:59.000Z

16

Quantum Field Theory on Certain Non-Globally Hyperbolic Spacetimes  

E-Print Network [OSTI]

We study real linear scalar field theory on two simple non-globally hyperbolic spacetimes containing closed timelike curves within the framework proposed by Kay for algebraic quantum field theory on non-globally hyperbolic spacetimes. In this context, a spacetime (M,g) is said to be `F-quantum compatible' with a field theory if it admits a *-algebra of local observables for that theory which satisfies a locality condition known as `F-locality'. Kay's proposal is that, in formulating algebraic quantum field theory on $(M,g)$, F-locality should be imposed as a necessary condition on the *-algebra of observables. The spacetimes studied are the 2- and 4-dimensional spacelike cylinders (Minkowski space quotiented by a timelike translation). Kay has shown that the 4-dimensional spacelike cylinder is F-quantum compatible with massless fields. We prove that it is also F-quantum compatible with massive fields and prove the F-quantum compatibility of the 2-dimensional spacelike cylinder with both massive and massless fields. In each case, F-quantum compatibility is proved by constructing a suitable F-local algebra.

C. J. Fewster; A. Higuchi

1995-08-24T23:59:59.000Z

17

Lorentz symmetry breaking as a quantum field theory regulator  

Science Journals Connector (OSTI)

Perturbative expansions of quantum field theories typically lead to ultraviolet (short-distance) divergences requiring regularization and renormalization. Many different regularization techniques have been developed over the years, but most regularizations require severe mutilation of the logical foundations of the theory. In contrast, breaking Lorentz invariance, while it is certainly a radical step, at least does not damage the logical foundations of the theory. I shall explore the features of a Lorentz symmetry breaking regulator in a simple polynomial scalar field theory and discuss its implications. In particular, I shall quantify just how much Lorentz symmetry breaking is required to fully regulate the quantum theory and render it finite. This scalar field theory provides a simple way of understanding many of the key features of Ho?avas recent article [Phys. Rev. D 79, 084008 (2009)] on 3+1 dimensional quantum gravity.

Matt Visser

2009-07-23T23:59:59.000Z

18

Quantum field theory on a growing lattice  

E-Print Network [OSTI]

We construct the classical and canonically quantized theories of a massless scalar field on a background lattice in which the number of points--and hence the number of modes--may grow in time. To obtain a well-defined theory certain restrictions must be imposed on the lattice. Growth-induced particle creation is studied in a two-dimensional example. The results suggest that local mode birth of this sort injects too much energy into the vacuum to be a viable model of cosmological mode birth.

Brendan Z. Foster; Ted Jacobson

2004-08-06T23:59:59.000Z

19

Quantum Field and Cosmic Field-Finite Geometrical Field Theory of Matter Motion Part Three  

E-Print Network [OSTI]

This research establishes an operational measurement way to express the quantum field theory in a geometrical form. In four-dimensional spacetime continuum, the orthogonal rotation is defined. It forms two sets of equations: one set is geometrical equations, another set is the motion equations. The Lorentz transformation can be directly derived from the geometrical equations, and the proper time of general relativity is well expressed by time displacement field. By the motion equations, the typical time displacement field of matter motion is discussed. The research shows that the quantum field theory can be established based on the concept of orthogonal rotation. On this sense, the quantum matter motion in physics is viewed as the orthogonal rotation of spacetime continuum. In this paper, it shows that there are three typical quantum solutions. One is particle-like solution, one is generation-type solution, and one is pure wave type solution. For each typical solution, the force fields are different. Many fea...

Xiao, J

2005-01-01T23:59:59.000Z

20

Generalized Gravity I : Kinematical Setting and reformalizing Quantum Field Theory  

E-Print Network [OSTI]

The first part of this work deals with the development of a natural differential calculus on non-commutative manifolds. The second part extends the covariance and equivalence principle as well studies its kinematical consequences such as the arising of gauge theory. Furthermore, a manifestly causal and covariant formulation of quantum field theory is presented which surpasses the usual Hamiltonian and path integral construction. A particular representation of this theory on the kinematical structure developed in section three is moreover given.

Johan Noldus

2008-01-28T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


21

Quantum field theories around a large-Z nucleus  

Science Journals Connector (OSTI)

We analyze quantum electrodynamics around a hypothetical highly charged (Z?137) nucleus by treating it as an external source. In contrast with the foregoing analyses which rely on the one-particle theory we construct a framework which enables us to create the quantum-field-theoretic treatment of the system. To deal with such a nonperturbative question we develop novel truncation and approximation procedures. Keeping only the lowest partial wave of the electron and the photon fields we transcribe the system into the form of two-dimensional fermion theory. We further convert the theory into a two-dimensional boson theory by using a bosonization technique. We then argue that the semiclassical approximation in the resultant boson theory is reasonably good and in particular does take care of the quantum effects of the original fermion theory. We investigate the asymptotic particle state of the theory and find that electrons appear as topological solitons. By analyzing the boson theory with an external source classically we show that the ground state undergoes the phase transition at a certain value of Z (Z?150 for nucleus size ?20 fm) from the normal QED vacuum to an anomalous one which is characterized by the occurrence of real pair creation of electrons and positrons. Our result is confronted with the one obtained by the one-particle-theoretic treatment. Some comments are made on the possibility of understanding the peak structure in positron spectrum observed in heavy-ion collisions.

Yumi Hirata and Hisakazu Minakata

1986-10-15T23:59:59.000Z

22

Relative Entropy and Proximity of Quantum Field Theories  

E-Print Network [OSTI]

We study the question of how reliably one can distinguish two quantum field theories (QFTs). Each QFT defines a probability distribution on the space of fields. The relative entropy provides a notion of proximity between these distributions and quantifies the number of measurements required to distinguish between them. In the case of nearby conformal field theories, this reduces to the Zamolodchikov metric on the space of couplings. Our formulation quantifies the information lost under renormalization group flow from the UV to the IR and leads us to a quantification of fine-tuning. This formalism also leads us to a criterion for distinguishability of low energy effective field theories generated by the string theory landscape.

Balasubramanian, Vijay; Maloney, Alexander

2014-01-01T23:59:59.000Z

23

Relative Entropy and Proximity of Quantum Field Theories  

E-Print Network [OSTI]

We study the question of how reliably one can distinguish two quantum field theories (QFTs). Each QFT defines a probability distribution on the space of fields. The relative entropy provides a notion of proximity between these distributions and quantifies the number of measurements required to distinguish between them. In the case of nearby conformal field theories, this reduces to the Zamolodchikov metric on the space of couplings. Our formulation quantifies the information lost under renormalization group flow from the UV to the IR and leads us to a quantification of fine-tuning. This formalism also leads us to a criterion for distinguishability of low energy effective field theories generated by the string theory landscape.

Vijay Balasubramanian; Jonathan J. Heckman; Alexander Maloney

2014-10-24T23:59:59.000Z

24

Neutrino oscillations: Quantum mechanics vs. quantum field theory  

SciTech Connect (OSTI)

A consistent description of neutrino oscillations requires either the quantum-mechanical (QM) wave packet approach or a quantum field theoretic (QFT) treatment. We compare these two approaches to neutrino oscillations and discuss the correspondence between them. In particular, we derive expressions for the QM neutrino wave packets from QFT and relate the free parameters of the QM framework, in particular the effective momentum uncertainty of the neutrino state, to the more fundamental parameters of the QFT approach. We include in our discussion the possibilities that some of the neutrino's interaction partners are not detected, that the neutrino is produced in the decay of an unstable parent particle, and that the overlap of the wave packets of the particles involved in the neutrino production (or detection) process is not maximal. Finally, we demonstrate how the properly normalized oscillation probabilities can be obtained in the QFT framework without an ad hoc normalization procedure employed in the QM approach.

Akhmedov, Evgeny Kh.; Kopp, Joachim; ,

2010-01-01T23:59:59.000Z

25

Quantum Field Theory and Differential Geometry  

E-Print Network [OSTI]

We introduce the historical development and physical idea behind topological Yang-Mills theory and explain how a physical framework describing subatomic physics can be used as a tool to study differential geometry. Further, we emphasize that this phenomenon demonstrates that the interrelation between physics and mathematics have come into a new stage.

W. F. Chen

2008-03-10T23:59:59.000Z

26

Field Theory for a Deuteron Quantum Liquid  

E-Print Network [OSTI]

Based on general symmetry principles we study an effective Lagrangian for a neutral system of condensed spin-1 deuteron nuclei and electrons, at greater-than-atomic but less-than-nuclear densities. We expect such matter to be present in thin layers within certain low-mass brown dwarfs. It may also be produced in future shock-wave-compression experiments as an effective fuel for laser induced nuclear fusion. We find a background solution of the effective theory describing a net spin zero condensate of deuterons with their spins aligned and anti-aligned in a certain spontaneously emerged preferred direction. The spectrum of low energy collective excitations contains two spin waves with linear dispersions -- like in antiferromagnets -- as well as gapped longitudinal and transverse modes related to the Meissner effect -- like in superconductors. We show that counting of the Nambu-Goldstone modes of spontaneously broken internal and space-time symmetries obeys, in a nontrivial way, the rules of the Goldstone theorem for Lorentz non-invariant systems. We discuss thermodynamic properties of the condensate, and its potential manifestation in the low-mass brown dwarfs.

Lasha Berezhiani; Gregory Gabadadze; David Pirtskhalava

2010-03-03T23:59:59.000Z

27

Charges and Generators of Symmetry Transformations in Quantum Field Theory  

Science Journals Connector (OSTI)

Within the Wightman approach to quantum field theory, we review and clarify the properties of formal charges, defined as space integrals for the fourth component of a local current. The conditions for a formal charge to determine an operator (generator) are discussed, in connection with the well-known theorems of Goldstone and of Coleman. The symmetry transformations generated by this operatorgiven its existenceare also studied in some detail. For generators in a scattering theory, we prove their additivity and thus provide a simple way to characterize them from their matrix elements between one-particle states. This characterization allows an immediate construction of the unitary operators implementing the symmetry transformations, and implies that all internal symmetry groups are necessarily compact. We also indicate how to construct interacting fields having definite internal quantum numbers. The present status of the proof of Noether's theorem and of its converse is discussed in the light of the rather delicate properties of formal charges.

CLAUDIO A. ORZALESI

1970-10-01T23:59:59.000Z

28

Green function identities in Euclidean quantum field theory  

E-Print Network [OSTI]

Given a generic Lagrangian system of even and odd fields, we show that any infinitesimal transformation of its classical Lagrangian yields the identities which Euclidean Green functions of quantum fields satisfy.

G. Sardanashvily

2006-04-01T23:59:59.000Z

29

Quantum field theory in curved spacetime, the operator product expansion, and dark energy  

E-Print Network [OSTI]

To make sense of quantum field theory in an arbitrary (globally hyperbolic) curved spacetime, the theory must be formulated in a local and covariant manner in terms of locally measureable field observables. Since a generic curved spacetime does not possess symmetries or a unique notion of a vacuum state, the theory also must be formulated in a manner that does not require symmetries or a preferred notion of a ``vacuum state'' and ``particles''. We propose such a formulation of quantum field theory, wherein the operator product expansion (OPE) of the quantum fields is elevated to a fundamental status, and the quantum field theory is viewed as being defined by its OPE. Since the OPE coefficients may be better behaved than any quantities having to do with states, we suggest that it may be possible to perturbatively construct the OPE coefficients--and, thus, the quantum field theory. By contrast, ground/vacuum states--in spacetimes, such as Minkowski spacetime, where they may be defined--cannot vary analytically with the parameters of the theory. We argue that this implies that composite fields may acquire nonvanishing vacuum state expectation values due to nonperturbative effects. We speculate that this could account for the existence of a nonvanishing vacuum expectation value of the stress-energy tensor of a quantum field occurring at a scale much smaller than the natural scales of the theory.

S. Hollands; R. M. Wald

2008-05-22T23:59:59.000Z

30

The Formulation of Quantum Field Theory with no Renormalization of Masses and Coupling Constants of Fermions  

E-Print Network [OSTI]

The paper presents the formulation of quantum field theory without renormalization of masses and coupling constants of fermions. Counter-terms, compensating for divergent quantities in self-energy diagrams of fermions and vacuum polarization diagrams at all orders of the perturbation theory, appear in the appropriate Hamiltonians under the special time-dependent unitary transformation.

Neznamov, V P

2015-01-01T23:59:59.000Z

31

Quantum field theory solution for a short-range interacting SO(3) quantum spin-glass  

E-Print Network [OSTI]

We study the quenched disordered magnetic system, which is obtained from the 2D SO(3) quantum Heisenberg model, on a square lattice, with nearest neighbors interaction, by taking a Gaussian random distribution of couplings centered in an antiferromagnetic coupling, $\\bar J>0$ and with a width $\\Delta J$. Using coherent spin states we can integrate over the random variables and map the system onto a field theory, which is a generalization of the SO(3) nonlinear sigma model with different flavors corresponding to the replicas, coupling parameter proportional to $\\bar J$ and having a quartic spin interaction proportional to the disorder ($\\Delta J$). After deriving the CP$^1$ version of the system, we perform a calculation of the free energy density in the limit of zero replicas, which fully includes the quantum fluctuations of the CP$^1$ fields $z_i$. We, thereby obtain the phase diagram of the system in terms of ($T, \\bar J, \\Delta J$). This presents an ordered antiferromagnetic (AF) phase, a paramagnetic (PM) phase and a spin-glass (SG) phase. A critical curve separating the PM and SG phases ends at a quantum critical point located between the AF and SG phases, at T=0. The Edwards-Anderson order parameter, as well as the magnetic susceptibilities are explicitly obtained in each of the three phases as a function of the three control parameters. The magnetic susceptibilities show a Curie-type behavior at high temperatures and exhibit a clear cusp, characteristic of the SG transition, at the transition line. The thermodynamic stability of the phases is investigated by a careful analysis of the Hessian matrix of the free energy. We show that all principal minors of the Hessian are positive in the limit of zero replicas, implying in particular that the SG phase is stable.

C. M. S. da Conceio; E. C. Marino

2009-03-02T23:59:59.000Z

32

Pascual Jordan's legacy and the ongoing research in quantum field theory  

E-Print Network [OSTI]

Pascual Jordan's path-breaking role as the protagonist of quantum field theory (QFT) is recalled and his friendly dispute with Dirac's particle-based relativistic quantum theory is presented as the start of the field-particle conundrum which, though in modified form, persists up to this date. Jordan had an intuitive understanding that the existence of a causal propagation with finite propagation speed in a quantum theory led to radically different physical phenomena than those of QM. The conceptional-mathematical understanding for such an approach began to emerge only 30 years later. The strongest link between Jordan's view of QFT and modern "local quantum physics" is the central role of causal locality as the defining principle of QFT as opposed to the Born localization in QM. The issue of causal localization is also the arena where misunderstandings led to a serious derailment of large part of particle theory e.g. the misinterpretation of an infinite component pointlike field resulting from the quantization of the Nambu-Goto Lagrangian as a spacetime quantum string. The new concept of modular localization, which replaces Jordan's causal locality, is especially important to overcome the imperfections of gauge theories for which Jordan was the first to note nonlocal aspects of physical (not Lagrangian) charged fields. Two interesting subjects in which Jordan was far ahead of his contemporaries will be presented in two separate sections.

Bert Schroer

2010-10-21T23:59:59.000Z

33

New Regulators for Quantum Field Theories with Compactified Extra Dimensions. II: Ultraviolet Finiteness and Effective Field Theory Implementation  

E-Print Network [OSTI]

In a previous companion paper [arXiv:0712.3532], we proposed two new regulators for quantum field theories in spacetimes with compactified extra dimensions. Unlike most other regulators which have been used in the extra-dimension literature, these regulators are specifically designed to respect the original higher-dimensional Lorentz and gauge symmetries that exist prior to compactification, and not merely the four-dimensional symmetries which remain afterward. In this paper, we use these regulators in order to develop a method for extracting ultraviolet-finite results from one-loop calculations. This method also allows us to derive Wilsonian effective field theories for Kaluza-Klein modes at different energy scales. Our method operates by ensuring that divergent corrections to parameters describing the physics of the excited Kaluza-Klein modes are absorbed into the corresponding parameters for zero modes, thereby eliminating the need to introduce independent counterterms for parameters characterizing different Kaluza-Klein modes. Our effective field theories can therefore simplify calculations involving Kaluza-Klein modes, and be compared directly to potential experimental results emerging from collider data.

Sky Bauman; Keith R. Dienes

2008-01-27T23:59:59.000Z

34

Particle detectors in curved spacetime quantum field theory  

E-Print Network [OSTI]

Unruh-DeWitt particle detector models are studied in a variety of time-dependent and time-independent settings. We work within the framework of first-order perturbation theory and couple the detector to a massless scalar field. The necessity of switching on (off) the detector smoothly is emphasised throughout, and the transition rate is found by taking the sharp-switching limit of the regulator-free and finite response function. The detector is analysed on a variety of spacetimes: $d$-dimensional Minkowski, the Ba\\~nados-Teitelboim-Zanelli (BTZ) black hole, the two-dimensional Minkowski half-plane, two-dimensional Minkowski with a receding mirror, and the two- and four-dimensional Schwarzschild black holes. In $d$-dimensional Minkowski spacetime, the transition rate is found to be finite up to dimension five. In dimension six, the transition rate diverges unless the detector is on a trajectory of constant proper acceleration, and the implications of this divergence to the global embedding spacetime (GEMS) methods are studied. In three-dimensional curved spacetime, the transition rate for the scalar field in an arbitrary Hadamard state is found to be finite and regulator-free. Then on the Ba\\~nados-Teitelboim-Zanelli (BTZ) black hole spacetime, we analyse the detector coupled to the field in the Hartle-Hawking vacua, under both transparent and reflective boundary conditions at infinity. Results are presented for the co-rotating detector, which responds thermally, and for the radially-infalling detector. In four-dimensional Schwarzschild spacetime, we proceed numerically, and the Hartle-Hawking, Boulware and Unruh vacua rates are compared. Results are presented for the case of the static detectors, which respond thermally, and also for the case of co-rotating detectors.

Lee Hodgkinson

2013-09-27T23:59:59.000Z

35

Particle detectors in curved spacetime quantum field theory  

E-Print Network [OSTI]

Unruh-DeWitt particle detector models are studied in a variety of time-dependent and time-independent settings. We work within the framework of first-order perturbation theory and couple the detector to a massless scalar field. The necessity of switching on (off) the detector smoothly is emphasised throughout, and the transition rate is found by taking the sharp-switching limit of the regulator-free and finite response function. The detector is analysed on a variety of spacetimes: $d$-dimensional Minkowski, the Ba\\~nados-Teitelboim-Zanelli (BTZ) black hole, the two-dimensional Minkowski half-plane, two-dimensional Minkowski with a receding mirror, and the two- and four-dimensional Schwarzschild black holes. In $d$-dimensional Minkowski spacetime, the transition rate is found to be finite up to dimension five. In dimension six, the transition rate diverges unless the detector is on a trajectory of constant proper acceleration, and the implications of this divergence to the global embedding spacetime (GEMS) met...

Hodgkinson, Lee

2013-01-01T23:59:59.000Z

36

Dynamical behavior of spatially inhomogeneous relativistic $? ?^4$ quantum field theory in the Hartree approximation  

E-Print Network [OSTI]

We study the dynamics of a spatially inhomogeneous quantum $\\lambda \\phi^4$ field theory in 1+1 dimensions in the Hartree approximation. In particular, we investigate the long-time behavior of this approximation in a variety of controlled situations, both at zero and finite temperature. The observed behavior is much richer than that in the spatially homogeneous case. Nevertheless, we show that the fields fail to thermalize in a canonical sense, as expected from analogous results in closely related (mean field) transport theory. We argue that this dynamical approximation is best suited as a means to study the short-time decay of spatially inhomogeneous fields and in the dynamics of coherent quasi-classical inhomogeneous configurations (e.g. solitons) in a background of dynamical self-consistent quantum fluctuations.

Luis M. A. Bettencourt; Karen Pao; J. G. Sanderson

2001-04-21T23:59:59.000Z

37

Relativistic Quantum Field Theory with a Physical State Vector  

E-Print Network [OSTI]

Evolution of a physical quantum state vector is described as governed by two distinct physical laws: Continuous, unitary time evolution and a relativistically covariant reduction process. In previous literature, it was concluded that a relativistically satisfactory version of the collapse postulate is in contradiction with physical measurements of a non-local state history. Here it is shown that such measurements are excluded when reduction is formulated as a physical process and the measurement devices are included as part of the state vector.

Bernd A. Berg

1998-07-17T23:59:59.000Z

38

4d index to 3d index and 2d topological quantum field theory  

Science Journals Connector (OSTI)

We compute the 4d superconformal index for N=1, 2 gauge theories on S1L(p,1), where L(p,1) is a lens space. We find that the 4d N=1, 2 index on S1L(p,1) reduces to a 3d N=2, 4 index on S1S2 in the large p limit, and to a 3d partition function on a squashed L(p,1) when the size of the temporal S1 shrinks to zero. As an application of our index, we study 4d N=2 superconformal field theories arising from the 6d N=(2,0) A1 theory on a punctured Riemann surface ?, and conjecture the existence of a 2d topological quantum field theory on ? whose correlation function coincides with the 4d N=2 index on S1L(p,1).

Francesco Benini; Tatsuma Nishioka; Masahito Yamazaki

2012-09-10T23:59:59.000Z

39

From Quantum Field Theory to Nano-Optics : Refractive Properties of Graphene in a Medium-Strong Magnetic field  

E-Print Network [OSTI]

1-loop quantum corrections are shown to induce large effects on the refraction index n inside a graphene strip in the presence of an external magnetic field B orthogonal to it. To this purpose, we use the tools of Quantum Field Theory to calculate the photon propagator at 1-loop inside graphene in position space, which leads to an effective vacuum polarization in a brane-like theory of photons interacting with massless electrons at locations confined inside the thin strip (its longitudinal spread is considered to be infinite). The effects factorize into quantum ones, controlled by the value of B and that of the electromagnetic coupling alpha, and a "transmittance function" U in which the geometry of the sample and the resulting confinement of electrons play the major roles. We consider photons inside the visible spectrum and magnetic fields in the range 1-20 Teslas. At B=0, quantum effects depend very weakly on alpha and n is essentially controlled by U; we recover, then, an opacity for visible light of the same order of magnitude pi * alpha_{vac} as measured experimentally.

Olivier Coquand; Bruno Machet

2014-07-08T23:59:59.000Z

40

A Self-Consistent Formulation of Quantum Field Theory on $S_{4}$  

E-Print Network [OSTI]

Recent developments in quantum gravity suggest that wormholes may influence the observed values of the constants of nature. The Euclidean formulation of quantum gravity predicts that wormholes induce a probability distribution in the space of possible fundamental constants. This distribution may computed by evaluating the functional integral about the stationary points of the action. In particular, the effective action on a large spherical space may lead to the vanishing of the cosmological constant and possibly determine the values of other constants of nature. The ability to perform calculations involving interacting quantum fields, particularly non-Abelian models, on a four-sphere is vital if one is to investigate this possibility. In this paper we present a self-consistent formulation of field theory on a four-sphere using the angular momentum space representation of $SO(5)$. We give a review of field theory on a sphere and then show how a matrix element prescription in angular momentum space overcomes previous limitations in calculational techniques. The standard one-loop graphs of QED are given as examples.

B. A. Harris; G. C. Joshi

1992-12-02T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


41

Ambiguities and Subtleties in Fermion Mass Terms in Practical Quantum Field Theory  

E-Print Network [OSTI]

This is a review on structure of the fermion mass terms in quantum field theory, under the perspective of its practical applications in the real physics of Nature -- specifically, we discuss fermion mass structure in the Standard Model of high energy physics, which successfully describes fundamental physics up to the TeV scale. The review is meant to be pedagogical, with detailed mathematics presented beyond the level one can find any easily in the textbooks. The discussions, however, bring up important subtleties and ambiguities about the subject that may be less than well appreciated. In fact, the naive perspective of the nature and masses of fermions as one would easily drawn from the presentations of fermion fields and their equations of motion from a typical textbook on quantum field theory leads to some confusing or even wrong statements which we clarify here. In particular, we illustrate clearly that a Dirac fermion mass eigenstate is mathematically equivalent to two degenerated Majorana fermion mass eigenstates at least so long as the mass terms are concerned. There are further ambiguities and subtleties in the exact description of the eigenstate(s). Especially, for the case of neutrinos, the use of the Dirac or Majorana terminology may be mostly a matter of choice. The common usage of such terminology is rather based on the broken $SU(2)$ charges of the related Weyl spinors hence conventional and may not be unambiguously extended to cover more complicate models.

Yifan Cheng; Otto C. W. Kong

2014-08-05T23:59:59.000Z

42

Negative energy densities in integrable quantum field theories at one-particle level  

E-Print Network [OSTI]

We study the phenomenon of negative energy densities in quantum field theories with self-interaction. Specifically, we consider a class of integrable models (including the sinh-Gordon model) in which we investigate the expectation value of the energy density in one-particle states. In this situation, we classify the possible form of the stress-energy tensor from first principles. We show that one-particle states with negative energy density generically exist in non-free situations, and we establish lower bounds for the energy density (quantum energy inequalities). Demanding that these inequalities hold reduces the ambiguity in the stress-energy tensor, in some situations fixing it uniquely. Numerical results for the lowest spectral value of the energy density allow us to demonstrate how negative energy densities depend on the coupling constant and on other model parameters.

Bostelmann, Henning

2015-01-01T23:59:59.000Z

43

Quasi-Topological Quantum Field Theories and $Z_2$ Lattice Gauge Theories  

E-Print Network [OSTI]

We consider a two parameter family of $Z_2$ gauge theories on a lattice discretization $T(M)$ of a 3-manifold $M$ and its relation to topological field theories. Familiar models such as the spin-gauge model are curves on a parameter space $\\Gamma$. We show that there is a region $\\Gamma_0$ of $\\Gamma$ where the partition function and the expectation value $$ of the Wilson loop for a curve $\\gamma$ can be exactly computed. Depending on the point of $\\Gamma_0$, the model behaves as topological or quasi-topological. The partition function is, up to a scaling factor, a topological number of $M$. The Wilson loop on the other hand, does not depend on the topology of $\\gamma$. However, for a subset of $\\Gamma_0$, $$ depends on the size of $\\gamma$ and follows a discrete version of an area law. At the zero temperature limit, the spin-gauge model approaches the topological and the quasi-topological regions depending on the sign of the coupling constant.

Miguel J. B. Ferreira; Victor A. Pereira; P. Teotonio-Sobrinho

2012-06-11T23:59:59.000Z

44

Engineering the unitary charge-conjugation operator of quantum field theory for particle-antiparticle using trapped ions and light fields in cavity QED  

E-Print Network [OSTI]

We present a method to engineer the unitary charge conjugation operator, as given by quantum field theory, in the highly controlled context of quantum optics, thus allowing one to simulate the creation of charged particles with well-defined momenta simultaneously with their respective antiparticles. Our method relies on trapped ions driven by a laser field and interacting with a single mode of a light field in a high Q cavity.

N. G. de Almeida

2014-01-22T23:59:59.000Z

45

Asymptotic states and renormalization in Lorentz-violating quantum field theory  

E-Print Network [OSTI]

Asymptotic single-particle states in quantum field theories with small departures from Lorentz symmetry are investigated perturbatively with focus on potential phenomenological ramifications. To this end, one-loop radiative corrections for a sample Lorentz-violating Lagrangian contained in the Standard-Model Extension (SME) are studied at linear order in Lorentz breakdown. It is found that the spinor kinetic operator, and thus the free-particle physics, is modified by Lorentz-violating operators absent from the original Lagrangian. As a consequence of this result, both the standard renormalization procedure as well as the Lehmann-Symanzik-Zimmermann reduction formalism need to be adapted. The necessary adaptations are worked out explicitly at first order in Lorentz-breaking coefficients.

Mauro Cambiaso; Ralf Lehnert; Robertus Potting

2014-01-28T23:59:59.000Z

46

Physics as Quantum Information Processing: Quantum Fields as Quantum Automata  

E-Print Network [OSTI]

Can we reduce Quantum Field Theory (QFT) to a quantum computation? Can physics be simulated by a quantum computer? Do we believe that a quantum field is ultimately made of a numerable set of quantum systems that are unitarily interacting? A positive answer to these questions corresponds to substituting QFT with a theory of quantum cellular automata (QCA), and the present work is examining this hypothesis. These investigations are part of a large research program on a "quantum-digitalization" of physics, with Quantum Theory as a special theory of information, and Physics as emergent from the same quantum-information processing. A QCA-based QFT has tremendous potential advantages compared to QFT, being quantum "ab-initio" and free from the problems plaguing QFT due to the continuum hypothesis. Here I will show how dynamics emerges from the quantum processing, how the QCA can reproduce the Dirac-field phenomenology at large scales, and the kind of departures from QFT that that should be expected at a Planck-scale discreteness. I will introduce the notions of linear field quantum automaton and local-matrix quantum automaton, in terms of which I will provide the solution to the Feynman's problem about the possibility of simulating a Fermi field with a quantum computer.

Giacomo Mauro D'Ariano

2011-10-31T23:59:59.000Z

47

Accurate nonadiabatic quantum dynamics on the cheap: making the most of mean field theory with master equations  

E-Print Network [OSTI]

In this article we show how Ehrenfest mean field theory can be made both a more accurate and efficient method to treat nonadiabatic quantum dynamics by combining it with the generalized quantum master equation framework. The resulting mean field generalized quantum master equation (MF-GQME) approach is a non-perturbative and non-Markovian theory that can be applied to open quantum systems without requiring a particular form of the interactions. By studying relaxation dynamics in a wide range of dynamical regimes, typical of charge and energy transfer, we show that MF-GQME provides a much higher accuracy than a direct application of mean field theory. In addition, these increases in accuracy are accompanied by computational speed-ups of between one and two orders of magnitude that become larger as the system becomes more nonadiabatic. This combination of quantum-classical theory and master equation techniques thus makes it possible to obtain the accuracy of much more computationally expensive approaches at a c...

Kelly, Aaron; Markland, Thomas E

2015-01-01T23:59:59.000Z

48

Unitarity Bounds and RG Flows in Time Dependent Quantum Field Theory  

SciTech Connect (OSTI)

We generalize unitarity bounds on operator dimensions in conformal field theory to field theories with spacetime dependent couplings. Below the energy scale of spacetime variation of the couplings, their evolution can strongly affect the physics, effectively shifting the infrared operator scaling and unitarity bounds determined from correlation functions in the theory. We analyze this explicitly for large-N double-trace flows, and connect these to UV complete field theories. One motivating class of examples comes from our previous work on FRW holography, where this effect explains the range of flavors allowed in the dual, time dependent, field theory.

Dong, Xi; Horn, Bart; Silverstein, Eva; Torroba, Gonzalo; /Stanford U., ITP /Stanford U., Phys. Dept. /SLAC

2012-04-05T23:59:59.000Z

49

The Casimir effect from the point of view of algebraic quantum field theory  

E-Print Network [OSTI]

We consider a region of Minkowski spacetime bounded either by one or by two parallel, infinitely extended plates orthogonal to a spatial direction and a real Klein-Gordon field satisfying Dirichlet boundary conditions. We quantize these two systems within the algebraic approach to quantum field theory using the so-called functional formalism. As a first step we construct a suitable unital *-algebra of observables whose generating functionals are characterized by a labeling space which is at the same time optimal and separating. Subsequently we give a definition for these systems of Hadamard states and we investigate explicit examples. In the case of a single plate, it turns out that one can build algebraic states via a pull-back of those on the whole Minkowski spacetime, moreover inheriting from them the Hadamard property. When we consider instead two plates, algebraic states can be put in correspondence with those on flat spacetime via the so-called method of images, which we translate to the algebraic setting. For a massless scalar field we show that this procedure works perfectly for a large class of quasi-free states including the Poincar\\'e vacuum and KMS states. Eventually we use our results in both systems to introduce the notion of Wick polynomials, showing that a global extended algebra does not exist. Furthermore we construct explicitly the two-point function and the regularized energy density, showing, moreover, that the outcome is consistent with the standard results of the Casimir effect.

Claudio Dappiaggi; Gabriele Nosari; Nicola Pinamonti

2014-12-03T23:59:59.000Z

50

New Regulators for Quantum Field Theories with Compactified Extra Dimensions. I: Fundamentals  

E-Print Network [OSTI]

In this paper, we propose two new regulators for quantum field theories in spacetimes with compactified extra dimensions. We refer to these regulators as the ``extended hard cutoff'' (EHC) and ``extended dimensional regularization'' (EDR). Although based on traditional four-dimensional regulators, the key new feature of these higher-dimensional regulators is that they are specifically designed to handle mixed spacetimes in which some dimensions are infinitely large and others are compactified. Moreover, unlike most other regulators which have been used in the extra-dimension literature, these regulators are designed to respect the original higher-dimensional Lorentz and gauge symmetries that exist prior to compactification, and not merely the four-dimensional symmetries which remain afterward. This distinction is particularly relevant for calculations of the physics of the excited Kaluza-Klein modes themselves, and not merely their radiative effects on zero modes. By respecting the full higher-dimensional symmetries, our regulators avoid the introduction of spurious terms which would not have been easy to disentangle from the physical effects of compactification. As part of our work, we also derive a number of ancillary results. For example, we demonstrate that in a gauge-invariant theory, analogues of the Ward-Takahashi identity hold not only for the usual zero-mode (four-dimensional) photons, but for all excited Kaluza-Klein photons as well.

Sky Bauman; Keith R. Dienes

2007-12-20T23:59:59.000Z

51

Fields and Quantum Mechanics  

E-Print Network [OSTI]

The quantum field theories (QFT) constructed in [1,2] include phenomenology of interest. The constructions approximate: scattering by $1/r$ and Yukawa potentials in non-relativistic approximations; and the first contributing order of the Feynman series for Compton scattering. To have a semi-norm, photon states are constrained to transverse polarizations and for Compton scattering, the constructed cross section deviates at large momentum exchanges from the cross section prediction of the Feynman rules. Discussion includes the incompatibility of canonical quantization with the constructed interacting fields, and the role of interpretations of quantum mechanics in realizing QFT.

Glenn Eric Johnson

2014-12-21T23:59:59.000Z

52

Quantum field theory in curved graphene spacetimes, Lobachevsky geometry, Weyl symmetry, Hawking effect, and all that  

E-Print Network [OSTI]

The solutions of many issues, of the ongoing efforts to make deformed graphene a tabletop quantum field theory in curved spacetimes, are presented. A detailed explanation of the special features of curved spacetimes, originating from embedding portions of the Lobachevsky plane into $\\mathbf{R}^3$, is given, and the special role of coordinates for the physical realizations in graphene, is explicitly shown, in general, and for various examples. The Rindler spacetime is reobtained, with new important differences with respect to earlier results. The de Sitter spacetime naturally emerges, for the first time, paving the way to future applications in cosmology. The role of the BTZ black hole is also briefly addressed. The singular boundary of the pseudospheres, "Hilbert horizon", is seen to be closely related to event horizon of the Rindler, de Sitter, and BTZ kind. This gives new, and stronger, arguments for the Hawking phenomenon to take place. An important geometric parameter, $c$, overlooked in earlier work, takes here its place for physical applications, and it is shown to be related to graphene's lattice spacing, $\\ell$. It is shown that all surfaces of constant negative curvature, ${\\cal K} = -r^{-2}$, are unified, in the limit $c/r \\to 0$, where they are locally applicable to the Beltrami pseudosphere. This, and $c = \\ell$, allow us a) to have a phenomenological control on the reaching of the horizon; b) to use spacetimes different than Rindler for the Hawking phenomenon; c) to approach the generic surface of the family. An improved expression for the thermal LDOS is obtained. A non-thermal term for the total LDOS is found. It takes into account: a) the peculiarities of the graphene-based Rindler spacetime; b) the finiteness of a laboratory surface; c) the optimal use of the Minkowski quantum vacuum, through the choice of this Minkowski-static boundary.

Alfredo Iorio; Gaetano Lambiase

2014-12-15T23:59:59.000Z

53

Finite temperature quantum field theory on non compact domains and application to delta interactionsinteractions in three dimensions  

E-Print Network [OSTI]

We use relative zeta functions technique of W. Muller \\cite{Mul} to extend the classical decomposition of the zeta regularized partition function of a finite temperature quantum field theory on a ultrastatic space-time with compact spatial section to the case of non compact spatial section. As an application, we study the case of Schr\\"odinger operators with delta like potential, as described by Albeverio & alt. in \\cite{AGHH}.

Mauro Spreafico; Sergio Zerbini

2007-08-30T23:59:59.000Z

54

A Proposed Alternative Low Energy Quantum Field Theory of Gravity Based on a Bose-Einstein Condensate Effect  

E-Print Network [OSTI]

An alternative quantum field theory for gravity is proposed for low energies based on an attractive effect between contaminants in a Bose-Einstein Condensate rather than on particle exchange. In the ``contaminant in condensate effect," contaminants cause a potential in an otherwise uniform condensate, forcing the condensate between two contaminants to a higher energy state. The energy of the system decreases as the contaminants come closer together, causing an attractive force between contaminants. It is proposed that mass-energy may have a similar effect on Einstein's space-time field, and gravity is quantized by the same method by which the contaminant in condensate effect is quantized. The resulting theory is finite and, if a physical condensate is assumed to underly the system, predictive. However, the proposed theory has several flaws at high energies and is thus limited to low energies. Falsifiable predictions are given for the case that the Higgs condensate is assumed to be the condensate underlying gravity.

Alexander Oshmyansky

2007-03-08T23:59:59.000Z

55

Theory of terahertz/near-infrared optical mixing in quantum wells in strong magnetic fields Takeshi Inoshita, Junichiro Kono,* and Hiroyuki Sakaki  

E-Print Network [OSTI]

Theory of terahertz/near-infrared optical mixing in quantum wells in strong magnetic fields TakeshiAs quantum wells illuminated simultaneously by near-infrared and terahertz THz radiation in strong magnetic the sample is illuminated simul- taneously by THz frequency T) and near-infrared fre- quency N) radiation

Kono, Junichiro

56

Quantum fields in curved spacetime  

E-Print Network [OSTI]

We review the theory of quantum fields propagating in an arbitrary, classical, globally hyperbolic spacetime. Our review emphasizes the conceptual issues arising in the formulation of the theory and presents known results in a mathematically precise way. Particular attention is paid to the distributional nature of quantum fields, to their local and covariant character, and to microlocal spectrum conditions satisfied by physically reasonable states. We review the Unruh and Hawking effects for free fields, as well as the behavior of free fields in deSitter spacetime and FLRW spacetimes with an exponential phase of expansion. We review how nonlinear observables of a free field, such as the stress-energy tensor, are defined, as well as time-ordered-products. The "renormalization ambiguities" involved in the definition of time-ordered products are fully characterized. Interacting fields are then perturbatively constructed. Our main focus is on the theory of a scalar field, but a brief discussion of gauge fields is included. We conclude with a brief discussion of a possible approach towards a nonperturbative formulation of quantum field theory in curved spacetime and some remarks on the formulation of quantum gravity.

Stefan Hollands; Robert M. Wald

2014-06-10T23:59:59.000Z

57

Quantum Decision Theory  

E-Print Network [OSTI]

We argue that, contrary to conventional wisdom, decision theory is not invariant to the physical environment in which a decision is made. Specifically, we show that a decision maker (DM) with access to quantum information resources may be able to do strictly better than a DM with access only to classical information resources. In this respect, our findings are somewhat akin to those in computer science that have established the superiority of quantum over classical algorithms for certain problems. We treat three kinds of decision tree (Kuhn [1950], [1953]): Kuhn trees in which the DM does or does not have perfect recall, and non-Kuhn trees.

Adam Brandenburger; Pierfrancesco La Mura

2011-07-01T23:59:59.000Z

58

Chameleon Field Theories  

E-Print Network [OSTI]

Chameleons are light scalar fields with remarkable properties. Through the interplay of self-interactions and coupling to matter, chameleon particles have a mass that depends on the ambient matter density. The manifestation of the fifth force mediated by chameleons therefore depends sensitively on their environment, which makes for a rich phenomenology. In this article, we review two recent results on chameleon phenomenology. The first result a pair of no-go theorems limiting the cosmological impact of chameleons and their generalizations: i) the range of the chameleon force at cosmological density today can be at most ~Mpc; ii) the conformal factor relating Einstein- and Jordan-frame scale factors is essentially constant over the last Hubble time. These theorems imply that chameleons have negligible effect on the linear growth of structure, and cannot account for the observed cosmic acceleration except as some form of dark energy. The second result pertains to the quantum stability of chameleon theories. We ...

Khoury, Justin

2013-01-01T23:59:59.000Z

59

Quantum dynamics with fermion coupled coherent states: Theory and application to electron dynamics in laser fields  

SciTech Connect (OSTI)

We present an alternate version of the coupled-coherent-state method, specifically adapted for solving the time-dependent Schroedinger equation for multielectron dynamics in atoms and molecules. This theory takes explicit account of the exchange symmetry of fermion particles, and it uses fermion molecular dynamics to propagate trajectories. As a demonstration, calculations in the He atom are performed using the full Hamiltonian and accurate experimental parameters. Single- and double-ionization yields by 160-fs and 780-nm laser pulses are calculated as a function of field intensity in the range 10{sup 14}-10{sup 16} W/cm{sup 2}, and good agreement with experiments by Walker et al. is obtained. Since this method is trajectory based, mechanistic analysis of the dynamics is straightforward. We also calculate semiclassical momentum distributions for double ionization following 25-fs and 795-nm pulses at 1.5x10{sup 15} W/cm{sup 2}, in order to compare them with the detailed experiments by Rudenko et al. For this more challenging task, full convergence is not achieved. However, major effects such as the fingerlike structures in the momentum distribution are reproduced.

Kirrander, Adam [Laboratoire Aime Cotton du CNRS, Universite de Paris-Sud, Batiment 505, F-91405 Orsay (France); Shalashilin, Dmitrii V. [School of Chemistry, University of Leeds, Leeds LS2 9JT (United Kingdom)

2011-09-15T23:59:59.000Z

60

Informational derivation of quantum theory  

SciTech Connect (OSTI)

We derive quantum theory from purely informational principles. Five elementary axioms - causality, perfect distinguishability, ideal compression, local distinguishability, and pure conditioning - define a broad class of theories of information processing that can be regarded as standard. One postulate - purification - singles out quantum theory within this class.

Chiribella, Giulio; D'Ariano, Giacomo Mauro; Perinotti, Paolo [Perimeter Institute for Theoretical Physics, 31 Caroline Street North, Ontario, N2L 2Y5 (Canada); QUIT Group, Dipartimento di Fisica ''A. Volta'' and INFN Sezione di Pavia, via Bassi 6, I-27100 Pavia (Italy)

2011-07-15T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


61

Quantum Probability from Decision Theory?  

E-Print Network [OSTI]

In a recent paper (quant-ph/9906015), Deutsch claims to derive the "probabilistic predictions of quantum theory" from the "non-probabilistic axioms of quantum theory" and the "non-probabilistic part of classical decision theory." We show that his derivation fails because it includes hidden probabilistic assumptions.

H. Barnum; C. M. Caves; J. Finkelstein; C. A. Fuchs; R. Schack

1999-07-07T23:59:59.000Z

62

Quantum probability from decision theory?  

Science Journals Connector (OSTI)

...128. Cox, R. T. 1946 Probability, frequency, and reasonable...Finetti, B. 1972 Theory of probability, vols I and II. Wiley...1999 Quantum theory of probability and decisions. Proc. R...1972 The foundations of statistics. Dover. Von Neumann, J...

2000-01-01T23:59:59.000Z

63

Quantum proof systems and entanglement theory  

E-Print Network [OSTI]

Quantum complexity theory is important from the point of view of not only theory of computation but also quantum information theory. In particular, quantum multi-prover interactive proof systems are defined based on ...

Abolfathe Beikidezfuli, Salman

2009-01-01T23:59:59.000Z

64

Quantum Probability from Decision Theory?  

E-Print Network [OSTI]

Deutsch has recently (in quant-ph/9906015) offered a justification, based only on the non-probabilistic axioms of quantum theory and of classical decision theory, for the use of the standard quantum probability rules. In this note, this justification is examined.

J. Finkelstein

1999-07-01T23:59:59.000Z

65

Prequantum Classical Statistical Field Theory: Fundamentals  

SciTech Connect (OSTI)

We present fundamentals of a prequantum model with hidden variables of the classical field type. In some sense this is the comeback of classical wave mechanics. Our approach also can be considered as incorporation of quantum mechanics into classical signal theory. All quantum averages (including correlations of entangled systems) can be represented as classical signal averages and correlations.

Khrennikov, Andrei [International Center for Mathematical Modelling in Physics and Cognitive Sciences, Linnaeus University, Vaexjoe, S-35195 (Sweden)

2011-03-28T23:59:59.000Z

66

Theory of optical properties of II-VI semiconductor quantum dots containing a single magnetic ion in a strong magnetic field  

Science Journals Connector (OSTI)

We present a microscopic theory of the magnetic field dependence of the optical properties of IIVI semiconductor quantum dots containing a single magnetic (Mn) impurity. The single-particle electron and heavy-hole states are described exactly by two-dimensional harmonic oscillators in a magnetic field, the Mn ion is treated as a spin of an isoelectronic impurity, and the quantum dot anisotropy is included perturbatively. The electron-hole direct, short-, and long-range exchange electron-hole Coulomb interactions, as well as the short-range spin-spin contact exchange interaction of the electron and the hole with the magnetic impurity is included. The electron-hole-Mn states are expanded in a finite number of configurations controlled by the number of confined electronic quantum dot shells and the full interacting Hamiltonian is diagonalized numerically in this basis. The absorption and emission spectrum is predicted as a function of photon energy, magnetic field, number of confined shells, and anisotropy. It is shown that the magnetic-field-induced enhancement of the exchange interaction of the Mn spin with the exciton is largely canceled by increased electron-hole Coulomb interactions. The predicted weak magnetic field dependence of the spacing of emission lines agrees well with the results of the spin model at low magnetic fields but differs at higher magnetic fields. Correlations in the exciton-Mn complex are predicted to determine absorption spectra.

Anna H. Trojnar; Marek Korkusi?ski; Marek Potemski; Pawel Hawrylak

2012-04-06T23:59:59.000Z

67

Quantum decision theory as quantum theory of measurement  

E-Print Network [OSTI]

We present a general theory of quantum information processing devices, that can be applied to human decision makers, to atomic multimode registers, or to molecular high-spin registers. Our quantum decision theory is a generalization of the quantum theory of measurement, endowed with an action ring, a prospect lattice and a probability operator measure. The algebra of probability operators plays the role of the algebra of local observables. Because of the composite nature of prospects and of the entangling properties of the probability operators, quantum interference terms appear, which make actions noncommutative and the prospect probabilities non-additive. The theory provides the basis for explaining a variety of paradoxes typical of the application of classical utility theory to real human decision making. The principal advantage of our approach is that it is formulated as a self-consistent mathematical theory, which allows us to explain not just one effect but actually all known paradoxes in human decision making. Being general, the approach can serve as a tool for characterizing quantum information processing by means of atomic, molecular, and condensed-matter systems.

V. I. Yukalov; D. Sornette

2009-03-30T23:59:59.000Z

68

Path integral quantization of parametrised field theory  

E-Print Network [OSTI]

Free scalar field theory on a flat spacetime can be cast into a generally covariant form known as parametrised field theory in which the action is a functional of the scalar field as well as the embedding variables which describe arbitrary, in general curved, foliations of the flat spacetime. We construct the path integral quantization of parametrised field theory in order to analyse issues at the interface of quantum field theory and general covariance in a path integral context. We show that the measure in the Lorentzian path integral is non-trivial and is the analog of the Fradkin- Vilkovisky measure for quantum gravity. We construct Euclidean functional integrals in the generally covariant setting of parametrised field theory using key ideas of Schleich and show that our constructions imply the existence of non-standard `Wick rotations' of the standard free scalar field 2 point function. We develop a framework to study the problem of time through computations of scalar field 2 point functions. We illustrate our ideas through explicit computation for a time independent 1+1 dimensional foliation. Although the problem of time seems to be absent in this simple example, the general case is still open. We discuss our results in the contexts of the path integral formulation of quantum gravity and the canonical quantization of parametrised field theory.

Madhavan Varadarajan

2004-04-06T23:59:59.000Z

69

Quantum Theory and Spacelike Measurements  

E-Print Network [OSTI]

Experimentally observed violations of Bell inequalities rule out local realistic theories. Consequently, the quantum state vector becomes a strong candidate for providing an objective picture of reality. However, such an ontological view of quantum theory faces difficulties when spacelike measurements on entangled states have to be described, because time ordering of spacelike events can change under Lorentz-Poincar\\'e transformations. In the present paper it is shown that a necessary condition for consistency is to require state vector reduction on the backward light-cone. A fresh approach to the quantum measurement problem appears feasible within such a framework.

Bernd A. Berg

1998-01-04T23:59:59.000Z

70

Dynamic local-field factor of an electron liquid in the quantum versions of the Singwi-Tosi-Land-Sjlander and Vashishta-Singwi theories  

Science Journals Connector (OSTI)

We have investigated in detail the complex, dynamic local field G(q,?) of an electron liquid in the quantum versions of the Singwi-Tosi-Land-Sjlander (STLS) and Vashishta-Singwi (VS) theories. We have worked out the various analytical properties of G(q,?) and shown that the STLS and VS theories are the high-frequency limits of the quantum cases. Variation of G(q,?) with ? is found to be rather mild. Interestingly, the static local field G(q,0) exhibits, in the region of metallic densities, a peaked structure around q?2.8kF, in contrast to the monotonically increasing local-field factors of the STLS and VS theories. The height of the peak reaches values greater than 1, which causes the effective particle-hole interaction to become attractive. This gives rise to the possibility of a charge-density-wave instability. We also give a parametric representation of G(q,0), which fulfills exactly the compressibility sum rule.

A. Holas and Shafiqur Rahman

1987-02-15T23:59:59.000Z

71

Field Theory of Matter  

Science Journals Connector (OSTI)

A speculative field theory of matter is developed. Simple computational methods are used in a preliminary survey of its consequences. The theory exploits the known properties of leptons by means of a principle of symmetry between electrical and nucleonic charge. There are fundamental fields with spins 0, , 1. The spinless field is neutral. Spin and 1 fields can carry both electrical and nucleonic charge. The multiplicity of any nonzero charge is 3. Explicit dynamical mechanisms for the breakdown of unitary symmetry and for the muon-electron mass difference are given. A more general view of lepton properties is proposed. Mass relations for baryon and meson multiplets are derived, together with approximate couplings among the multiplets. The weakness of ? production in ?-N collisions and the suppression of the ???+? decay is explained.

Julian Schwinger

1964-08-10T23:59:59.000Z

72

No Drama Quantum Theory? A Review  

E-Print Network [OSTI]

Schr\\"{o}dinger (Nature, v.169, 538 (1952)) noted that the complex matter field in the Klein-Gordon equation can be made real by a gauge transform, although charged fields are believed to require complex functions. Surprisingly, the result can be extended to the Dirac equation: three complex components of the Dirac spinor function can be algebraically eliminated, and the remaining component can be made real by a gauge transform. Therefore, the Dirac equation is generally equivalent to one fourth-order partial differential equation for one real function (A. Akhmeteli, J. Math. Phys. v.52, 082303 (2011)). These results both belong in textbooks and can be used for development of new efficient methods of quantum chemistry. The matter field can be algebraically eliminated both in scalar electrodynamics and in spinor electrodynamics in a certain gauge. The resulting equations describe independent dynamics of the electromagnetic field, which permits mathematical simplification and can be useful for interpretation of quantum theory. For example, in the Bohm interpretation, the electromagnetic field can replace the wave function as the guiding field. It is also shown that for these equations, generalized Carleman embedding generates systems of linear equations in the Hilbert space, which look like second-quantized theories and are equivalent to the original nonlinear systems on the set of solutions of the latter. Thus, the relevant local realistic models can be embedded into quantum field theories. These models are equivalent to scalar electrodynamics and spinor electrodynamics, so they correctly describe a large body of experimental data. Although they may need some modifications for better agreement with experiments, they may be of great interest as "no drama quantum theories", as simple (in principle) as classical electrodynamics. Possible issues with the Bell theorem are discussed.

A. Akhmeteli

2011-11-20T23:59:59.000Z

73

Time independent mean-field theory  

SciTech Connect (OSTI)

The physical and theoretical motivations for the time-dependent mean-field theory are presented, and the successes and limitations of the time-dependent Hartree-Fock initial-vaue problem are reviewed. New theoretical developments are described in the treatment of two-body correlations and the formulation of a quantum mean-field theory of large-amplitude collective motion and tunneling decay. Finally, the mean-field theory is used to obtain new insights into the phenomenon of pion condensation in finite nuclei. 18 figures.

Negele, J.W.

1980-02-01T23:59:59.000Z

74

Copenhagen Quantum Mechanics Emerges from a Deterministic Schroedinger Theory in 11 Dimensional Spacetime Including Weak Field Gravitation  

E-Print Network [OSTI]

We construct a world model consisting of a matter field living in 4 dimensional spacetime and a gravitational field living in 11 dimensional spacetime. The seven hidden dimensions are compactified within a radius estimated by reproducing the particle - wave characteristic of diffraction experiments. In the presence of matter fields the gravitational field develops localized modes with elementary excitations called gravonons which are induced by the sources (massive particles). The final world model treated here contains only gravonons and a scalar matter field. The solution of the Schroedinger equation for the world model yields matter fields which are localized in the 4 dimensional subspace. The localization has the following properties: (i) There is a chooser mechanism for the selection of the localization site. (ii) The chooser selects one site on the basis of minor energy differences and differences in the gravonon structure between the sites, which appear statistical. (iii) The changes from one localization site to a neighbouring one take place in a telegraph-signal like manner. (iv) The times at which telegraph like jumps occur dependent on subtleties of the gravonon structure which appear statistical. (v) The fact that the dynamical law acts in the configuration space of fields living in 11 dimensional spacetime lets the events observed in 4 dimensional spacetime appear non-local. In this way the phenomenology of Copenhagen quantum mechanics is obtained without the need of introducing the process of collapse and a probabilistic interpretation of the wave function. Operators defining observables need not be introduced. All experimental findings are explained in a deterministic way as a consequence of the time development of the wave function in configuration space according to Schroedinger's equation.

Gerold Doyen; Deiana Drakova

2014-08-12T23:59:59.000Z

75

Interference and inequality in quantum decision theory  

E-Print Network [OSTI]

The quantum decision theory is examined in its simplest form of two-condition two-choice setting. A set of inequalities to be satisfied by any quantum conditional probability describing the decision process is derived. Experimental data indicating the breakdown of classical explanations are critically examined with quantum theory using the full set of quantum phases.

Taksu Cheon; Taiki Takahashi

2010-08-16T23:59:59.000Z

76

Born--Oppenheimer decomposition for quantum fields on quantum spacetimes  

E-Print Network [OSTI]

Quantum Field Theory on Curved Spacetime (QFT on CS) is a well established theoretical framework which intuitively should be a an extremely effective description of the quantum nature of matter when propagating on a given background spacetime. If one wants to take care of backreaction effects, then a theory of quantum gravity is needed. It is now widely believed that such a theory should be formulated in a non-perturbative and therefore background independent fashion. Hence, it is a priori a puzzle how a background dependent QFT on CS should emerge as a semiclassical limit out of a background independent quantum gravity theory. In this article we point out that the Born-Oppenheimer decomposition (BOD) of the Hilbert space is ideally suited in order to establish such a link, provided that the Hilbert space representation of the gravitational field algebra satisfies an important condition. If the condition is satisfied, then the framework of QFT on CS can be, in a certain sense, embedded into a theory of quantum gravity. The unique representation of the holonomy-flux algebra underlying Loop Quantum Gravity (LQG) violates that condition. While it is conceivable that the condition on the representation can be relaxed, for convenience in this article we consider a new classical gravitational field algebra and a Hilbert space representation of its restriction to an algebraic graph for which the condition is satisfied. An important question that remains and for which we have only partial answers is how to construct eigenstates of the full gravity-matter Hamiltonian whose BOD is confined to a small neighbourhood of a physically interesting vacuum spacetime.

Kristina Giesel; Johannes Tambornino; Thomas Thiemann

2009-11-27T23:59:59.000Z

77

Quantum Electrodynamical Density-Functional Theory: Bridging Quantum Optics and Electronic-Structure Theory  

E-Print Network [OSTI]

In this work we give a comprehensive derivation of an exact and numerically feasible method to perform ab-initio calculations of quantum particles interacting with a quantized electromagnetic field. We present a hierachy of density-functional-type theories that describe the interaction of charged particles with photons and introduce the appropriate Kohn-Sham schemes. We show how the evolution of a system described by quantum electrodynamics in Coulomb gauge is uniquely determined by its initial state and two reduced quantities. These two fundamental observables, the polarization of the Dirac field and the vector potential of the photon field, can be calculated by solving two coupled, non-linear evolution equations without the need to explicitly determine the (numerically infeasible) many-body wave function of the coupled quantum system. To find reliable approximations to the implicit functionals we present the according Kohn-Sham construction. In the non-relativistic limit this density-functional-type theory ...

Ruggenthaler, Michael; Pellegrini, Camilla; Appel, Heiko; Tokatly, Ilya V; Rubio, Angel

2014-01-01T23:59:59.000Z

78

The Quantum Field as a Quantum Computer  

E-Print Network [OSTI]

It is supposed that at very small scales a quantum field is an infinite homogeneous quantum computer. On a quantum computer the information cannot propagate faster than $c=a/\\tau$, $a$ and $\\tau$ being the minimum space and time distances between gates, respectively. It is shown that the information flow satisfies a Dirac equation, with speed $v=\\zeta c$ and $\\zeta=\\zeta(m)$ mass-dependent. For $a/\\tau=c$ the speed of light $\\zeta^{-1}$ is a vacuum refraction index increasing monotonically from $\\zeta^{-1}(0)=1$ to $\\zeta^{-1}(M)=\\infty$, $M$ being the Planck mass for $2a$ the Planck length.

Giacomo Mauro D'Ariano

2010-12-02T23:59:59.000Z

79

Energy and Momentum Density in Field Theory  

Science Journals Connector (OSTI)

It is shown that the energy density commutator condition in its simplest form is valid for interacting spin 0, , 1 field systems, but not for higher spin fields. The action principle is extended, for this purpose, to arbitrary coordinate frames. There is a discussion of four categories of fields and some explicit consideration of spin 32 as the simplest example that gives additional terms in the energy density commutator. As the fundamental equation of relativistic quantum field theory, the commutator condition makes explicit the greater physical complexity of higher spin fields.

Julian Schwinger

1963-04-15T23:59:59.000Z

80

Theory of Pseudomodes in Quantum Optical Processes  

E-Print Network [OSTI]

This paper deals with non-Markovian behaviour in atomic systems coupled to a structured reservoir of quantum EM field modes, with particular relevance to atoms interacting with the field in high Q cavities or photonic band gap materials. In cases such as the former, we show that the pseudo mode theory for single quantum reservoir excitations can be obtained by applying the Fano diagonalisation method to a system in which the atomic transitions are coupled to a discrete set of (cavity) quasimodes, which in turn are coupled to a continuum set of (external) quasimodes with slowly varying coupling constants and continuum mode density. Each pseudomode can be identified with a discrete quasimode, which gives structure to the actual reservoir of true modes via the expressions for the equivalent atom-true mode coupling constants. The quasimode theory enables cases of multiple excitation of the reservoir to now be treated via Markovian master equations for the atom-discrete quasimode system. Applications of the theory to one, two and many discrete quasimodes are made. For a simple photonic band gap model, where the reservoir structure is associated with the true mode density rather than the coupling constants, the single quantum excitation case appears to be equivalent to a case with two discrete quasimodes.

B. J. Dalton; S. M. Barnett; B. M. Garraway

2001-02-28T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


81

Quantum Monte Carlo calculations of electromagnetic moments and transitions in A{<=}9 nuclei including meson-exchange currents derived from chiral effective field theory  

SciTech Connect (OSTI)

Quantum Monte Carlo calculations of electromagnetic moments and transitions are reported for A{<=}9 nuclei. The realistic Argonne v{sub 18} two-nucleon and Illinois-7 three-nucleon potentials are used to generate the nuclear wave functions. Contributions of two-body meson-exchange current (MEC) operators are included for magnetic moments and M1 transitions. The MEC operators have been derived in both a standard nuclear physics approach and a chiral effective field theory formulation with pions and nucleons including up to one-loop corrections. The two-body MEC contributions provide significant corrections and lead to very good agreement with experiment. Their effect is particularly pronounced in the A=9, T=3/2 systems, in which they provide up to ~20% (~40%) of the total predicted value for the {sup 9}Li ({sup 9}C) magnetic moment.

Saori Pastore, S.C. Pieper, Rocco Schiavilla, Robert Wiringa

2013-03-01T23:59:59.000Z

82

Understanding conformal field theory through parafermions and Chern Simons theory  

SciTech Connect (OSTI)

Conformal field theories comprise a vast class of exactly solvable two dimensional quantum field theories. Conformal theories with an enlarged symmetry group, the current algebra symmetry, axe a key ingredient to possible string compactification models. The following work explores a Lagrangian approach to these theories. In the first part of this thesis, a large class of conformal theories, the so-called coset models, are derived semi-classically from a gauged version Of the Wess-Zumino-Witten functional. A non-local field transformation to the parafermionic field description is employed in the quantization procedure. Classically, these parafermionic fields satisfy non-trivial Poisson brackets, providing insight into the fractional spin nature of the conformal theory. The W-algebra symmetry is shown to appear naturally in this approach. In the second part of this thesis, the connection between the fusion algebra structure of Wess-Zumino-Witten models and the quantization of the Chern-Simons action on the torus is made explicit. The modular properties of the conformal model are also derived in this context, giving a natural demonstration of the Verlinde conjecture. The effects of background gauge fields and monopoles are also discussed.

Hotes, S.A.

1992-11-19T23:59:59.000Z

83

Quantum Theory of Probability and Decisions  

E-Print Network [OSTI]

The probabilistic predictions of quantum theory are conventionally obtained from a special probabilistic axiom. But that is unnecessary because all the practical consequences of such predictions follow from the remaining, non-probabilistic, axioms of quantum theory, together with the non-probabilistic part of classical decision theory.

David Deutsch

1999-06-04T23:59:59.000Z

84

Processing Information in Quantum Decision Theory  

E-Print Network [OSTI]

A survey is given summarizing the state of the art of describing information processing in Quantum Decision Theory, which has been recently advanced as a novel variant of decision making, based on the mathematical theory of separable Hilbert spaces. This mathematical structure captures the effect of superposition of composite prospects, including many incorporated intended actions. The theory characterizes entangled decision making, non-commutativity of subsequent decisions, and intention interference. The self-consistent procedure of decision making, in the frame of the quantum decision theory, takes into account both the available objective information as well as subjective contextual effects. This quantum approach avoids any paradox typical of classical decision theory. Conditional maximization of entropy, equivalent to the minimization of an information functional, makes it possible to connect the quantum and classical decision theories, showing that the latter is the limit of the former under vanishing interference terms.

V. I. Yukalov; D. Sornette

2008-02-25T23:59:59.000Z

85

Electromagnetic Field Theory  

E-Print Network [OSTI]

physicists around the world and from WWW `hit' statistics it seems that the book serves as a frequently used formulation of classical electrodynamics, force, momentum and energy of the electromagnetic field, radiation and scope to make it useful in higher university education anywhere in the world, it was produced within

Hart, Gus

86

Quantum mechanical effects from deformation theory  

SciTech Connect (OSTI)

We consider deformations of quantum mechanical operators by using the novel construction tool of warped convolutions. The deformation enables us to obtain several quantum mechanical effects where electromagnetic and gravitomagnetic fields play a role. Furthermore, a quantum plane can be defined by using the deformation techniques. This in turn gives an experimentally verifiable effect.

Much, A. [Max-Planck-Institute for Mathematics in the Sciences, 04103 Leipzig, Germany and Institute for Theoretical Physics, University of Leipzig, 04009 Leipzig (Germany)] [Max-Planck-Institute for Mathematics in the Sciences, 04103 Leipzig, Germany and Institute for Theoretical Physics, University of Leipzig, 04009 Leipzig (Germany)

2014-02-15T23:59:59.000Z

87

Quantum-classical correspondence in response theory  

E-Print Network [OSTI]

In this thesis, theoretical analysis of correspondence between classical and quantum dynamics is studied in the context of response theory. Thesis discusses the mathematical origin of time-divergence of classical response ...

Kryvohuz, Maksym

2008-01-01T23:59:59.000Z

88

Quantum Probability and Decision Theory, Revisited  

E-Print Network [OSTI]

An extended analysis is given of the program, originally suggested by Deutsch, of solving the probability problem in the Everett interpretation by means of decision theory. Deutsch's own proof is discussed, and alternatives are presented which are based upon different decision theories and upon Gleason's Theorem. It is argued that decision theory gives Everettians most or all of what they need from `probability'. Some consequences of (Everettian) quantum mechanics for decision theory itself are also discussed.

David Wallace

2002-11-18T23:59:59.000Z

89

Quantum theory from one global symmetry  

E-Print Network [OSTI]

It is shown that unitary quantum theory is not only consistent with but follows from decompositional equivalence: the principle that there is no preferred decomposition of the universe into systems, or alternatively, that there is no preferred quantum reference frame. Decompositional equivalence requires unitary quantum theory to be both observer- and scale-independent, requires time, "systems" and all classical information to be strictly observer-relative, and imposes an unavoidable free-energy cost on the acquisition of observational outcomes. This free energy cost of observation is characterized from first principles and shown to accord with known costs of information acquisition and storage by human observers.

Chris Fields

2014-06-17T23:59:59.000Z

90

Comments on Cahill's Quantum Foam Inflow Theory of Gravity  

E-Print Network [OSTI]

We reveal an underlying flaw in Reginald T. Cahill's recently promoted quantum foam inflow theory of gravity. It appears to arise from a confusion of the idea of the Galilean invariance of the acceleration of an individual flow with what is obtained as an acceleration when a homogeneous flow is superposed with an inhomogeneous flow. We also point out that the General Relativistic covering theory he creates by substituting a generalized Painleve-Gullstrand metric into Einstein's field equations leads to absurd results.

T. D. Martin

2004-07-20T23:59:59.000Z

91

Non-Equilibrium Conformal Field Theories with Impurities  

E-Print Network [OSTI]

We present a construction of non-equilibrium steady states within conformal field theory. These states sustain energy flows between two quantum systems, initially prepared at different temperatures, whose dynamical properties are represented by two, possibly different, conformal field theories connected through an impurity. This construction relies on a real time formulation of conformal defect dynamics based on a field scattering picture parallelizing - but yet different from - the Euclidean formulation. We present the basic characteristics of this formulation and give an algebraic construction of the real time scattering maps that we illustrate in the case of SU(2)-based conformal field theories.

D. Bernard; B. Doyon; J. Viti

2015-01-20T23:59:59.000Z

92

Quantum Theory of Matter: Superfluids & Superconductors  

E-Print Network [OSTI]

. The electrical resistance of a metal decreases when it is cooled. For a superconductor, the resistance vanishes resistance flux expulsion flux quantisation Superfluids atomic Bose condensates liquid helium theory in condensed matter physics elementary excitations in strongly correlated systems 1 Quantum Theory

93

Hamilton-Jacobi Theory in k-Symplectic Field Theories  

E-Print Network [OSTI]

In this paper we extend the geometric formalism of Hamilton-Jacobi theory for Mechanics to the case of classical field theories in the k-symplectic framework.

M. De Len; D. Martn De Diego; J. C. Marrero; M. Salgado; S. Vilario

2010-05-10T23:59:59.000Z

94

Quantum Theory of Synchroton Radiation  

Science Journals Connector (OSTI)

The classical relativistic expression for the synchrotron radiation spectrum has been generalized to include quantum corrections up to second order in ??/E [1]. The modifications can be traced to the discrete ...

Heimo G. Latal

1979-01-01T23:59:59.000Z

95

Quantum fields in toroidal topology  

SciTech Connect (OSTI)

The standard representation of c*-algebra is used to describe fields in compactified space-time dimensions characterized by topologies of the type {Gamma}{sub D}{sup d}=(S{sup 1}){sup d}xM{sup D-d}. The modular operator is generalized to introduce representations of isometry groups. The Poincare symmetry is analyzed and then we construct the modular representation by using linear transformations in the field modes, similar to the Bogoliubov transformation. This provides a mechanism for compactification of the Minkowski space-time, which follows as a generalization of the Fourier integral representation of the propagator at finite temperature. An important result is that the 2x2 representation of the real-time formalism is not needed. The end result on calculating observables is described as a condensate in the ground state. We initially analyze the free Klein-Gordon and Dirac fields, and then formulate non-abelian gauge theories in {Gamma}{sub D}{sup d}. Using the S-matrix, the decay of particles is calculated in order to show the effect of the compactification. - Highlights: > C*-algebra is used to describe fields in compactified space-time dimensions. > The space-time is characterized by toroidal topologies. > Representations of the Poincare group are studied by using the modular operator. > We derive non-abelian gauge theories in compactified regions of space-time. > We show the compactification effect in the decay of particles using the S-matrix.

Khanna, F.C., E-mail: fkhanna@ualberta.ca [Theoretical Physics Institute, University of Alberta, Edmonton, AB, T6G 2J1 (Canada); TRIUMF, Vancouver, BC, V6T 2A3 (Canada); Malbouisson, A.P.C., E-mail: adolfo@cbpf.br [Centro Brasileiro de Pesquisas Fisicas/MCT, 22290-180, Rio de Janeiro, RJ (Brazil); Malbouisson, J.M.C., E-mail: jmalboui@ufba.br [Instituto de Fisica, Universidade Federal da Bahia, 40210-340, Salvador, BA (Brazil); Santana, A.E., E-mail: asantana@unb.br [Theoretical Physics Institute, University of Alberta, Edmonton, AB, T6G 2J1 (Canada); Instituto de Fisica, International Center for Condensed Matter Physics, Universidade de Brasilia, 70910-900, Brasilia, DF (Brazil)

2011-10-15T23:59:59.000Z

96

Geometric Hamilton-Jacobi Field Theory  

E-Print Network [OSTI]

I briefly review my proposal about how to extend the geometric Hamilton-Jacobi theory to higher derivative field theories on fiber bundles.

Luca Vitagliano

2011-09-08T23:59:59.000Z

97

Derivation of Quantum Theory from Feynman's Rules  

E-Print Network [OSTI]

Feynman's formulation of quantum theory is remarkable in its combination of formal simplicity and computational power. However, as a formulation of the abstract structure of quantum theory, it is incomplete as it does not account for most of the fundamental mathematical structure of the standard von Neumann-Dirac formalism such as the unitary evolution of quantum states. In this paper, we show how to reconstruct the entirety of the finite-dimensional quantum formalism starting from Feynman's rules with the aid of a single new physical postulate, the no-disturbance postulate. This postulate states that a particular class of measurements have no effect on the outcome probabilities of subsequent measurements performed. We also show how it is possible to derive both the amplitude rule for composite systems of distinguishable subsystems and Dirac's amplitude-action rule, each from a single elementary and natural assumption, by making use of the fact that these assumptions must be consistent with Feynman's rules.

Philip Goyal

2014-03-14T23:59:59.000Z

98

Risk, ambiguity and quantum decision theory  

E-Print Network [OSTI]

In the present article we use the quantum formalism to describe the effects of risk and ambiguity in decision theory. The main idea is that the probabilities in the classic theory of expected utility are estimated probabilities, and thus do not follow the classic laws of probability theory. In particular, we show that it is possible to use consistently the classic expected utility formula, where the probability associated to the events are computed with the equation of quantum interference. Thus we show that the correct utility of a lottery can be simply computed by adding to the classic expected utility a new corrective term, the uncertainty utility, directly connected with the quantum interference term.

Riccardo Franco

2007-11-06T23:59:59.000Z

99

Bekenstein bound in asymptotically free field theory  

SciTech Connect (OSTI)

For spatially bounded free fields, the Bekenstein bound states that the specific entropy satisfies the inequality (S/E){<=}2{pi}R, where R stands for the radius of the smallest sphere that circumscribes the system. The validity of the Bekenstein bound in the asymptotically free side of the Euclidean ({lambda}{phi}{sup 4}){sub d} scalar field theory is investigated. We consider the system in thermal equilibrium with a reservoir at temperature {beta}{sup -1} and defined in a compact spatial region without boundaries. Using the effective potential, we discuss the thermodynamic of the model. For low and high temperatures the system presents a condensate. We present the renormalized mean energy E and entropy S for the system and show in which situations the specific entropy satisfies the quantum bound.

Arias, E.; Svaiter, N. F.; Menezes, G. [Centro Brasileiro de Pesquisas Fisicas-CBPF, Rua Dr. Xavier Sigaud 150, Rio de Janeiro, RJ, 22290-180 (Brazil); Instituto de Fisica Teorica, Universidade Estadual Paulista, Rua Dr. Bento Teobaldo Ferraz 271, Bloco II, Barra Funda, Sao Paulo, SP, 01140-070 (Brazil)

2010-08-15T23:59:59.000Z

100

Electric Field effects on quantum correlations in semiconductor quantum dots  

E-Print Network [OSTI]

We study the effect of external electric bias on the quantum correlations in the array of optically excited coupled semiconductor quantum dots. The correlations are characterized by the quantum discord and concurrence and are observed using excitonic qubits. We employ the lower bound of concurrence for thermal density matrix at different temperatures. The effect of the F\\"orster interaction on correlations will be studied. Our theoretical model detects nonvanishing quantum discord when the electric field is on while concurrence dies, ensuring the existence of nonclassical correlations as measured by the quantum discord.

S. Shojaei; M. Mahdian; R. Yousefjani

2012-05-01T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


101

Lattice p-Form Electromagnetism and Chain Field Theory  

E-Print Network [OSTI]

Since Wilson's work on lattice gauge theory in the 1970s, discrete versions of field theories have played a vital role in fundamental physics. But there is recent interest in certain higher dimensional analogues of gauge theory, such as p-form electromagnetism, including the Kalb-Ramond field in string theory, and its nonabelian generalizations. It is desirable to discretize such `higher gauge theories' in a way analogous to lattice gauge theory, but with the fundamental geometric structures in the discretization boosted in dimension. As a step toward studying discrete versions of more general higher gauge theories, we consider the case of p-form electromagnetism. We show that discrete p-form electromagnetism admits a simple algebraic description in terms of chain complexes of abelian groups. Moreover, the model allows discrete spacetimes with quite general geometry, in contrast to the regular cubical lattices usually associated with lattice gauge theory. After constructing a suitable model of discrete spacetime for p-form electromagnetism, we quantize the theory using the Euclidean path integral formalism. The main result is a description of p-form electromagnetism as a `chain field theory' -- a theory analogous to topological quantum field theory, but with chain complexes replacing manifolds. This, in particular, gives a notion of time evolution from one `spacelike slice' of discrete spacetime to another.

Derek K. Wise

2005-10-08T23:59:59.000Z

102

Tensor networks for Lattice Gauge Theories and Atomic Quantum Simulation  

E-Print Network [OSTI]

We show that gauge invariant quantum link models, Abelian and non-Abelian, can be exactly described in terms of tensor networks states. Quantum link models represent an ideal bridge between high-energy to cold atom physics, as they can be used in cold-atoms in optical lattices to study lattice gauge theories. In this framework, we characterize the phase diagram of a (1+1)-d quantum link version of the Schwinger model in an external classical background electric field: the quantum phase transition from a charge and parity ordered phase with non-zero electric flux to a disordered one with a net zero electric flux configuration is described by the Ising universality class.

E. Rico; T. Pichler; M. Dalmonte; P. Zoller; S. Montangero

2014-06-07T23:59:59.000Z

103

Relativistic Gravity and Non-Relativistic Effective Field Theories  

E-Print Network [OSTI]

There has been great interest recently in formulating non-relativistic effective field theories in a general coordinate invariant way. We show that relativistic gravity theories can offer such a framework. We focus on the parity violating case in 2+1 dimensions which is particularly appropriate for the study on quantum Hall effects and chiral superfluids. We discuss how the non-relativistic spacetime structure emerges from relativistic gravity. We present covariant maps and constraints that relate the field contents in the two theories, which also serve as holographic dictionary in context of gauge/gravity duality. A low energy effective action for fractional quantum Hall states is constructed and captures universal geometric properties and generates non-universal corrections systematically. We give another holographic example with dyonic black brane background to calculate thermodynamic and transport properties of strongly coupled non-relativistic fluids in magnetic field. Our formalism has a good projection...

Wu, Chaolun

2014-01-01T23:59:59.000Z

104

Natural Philosophy and Quantum Theory  

E-Print Network [OSTI]

We attempt to show how relationalism might help in understanding Bell's theorem. We also present an analogy with Darwinian evolution in order to pedagogically hint at how one might go about using a theory in which one does not even desire to explain correlations by invoking common causes.

Thomas Marlow

2006-08-22T23:59:59.000Z

105

Quantum theory of optical coherence of nonstationary light in the space-frequency domain  

SciTech Connect (OSTI)

Classical theories of coherence for statistically stationary, as well as, nonstationary optical fields are frequently discussed both in the space-time and in the space-frequency domains. However, the quantum treatment of coherence theory is generally carried out in the space-time domain. In this paper, we present a quantum-mechanical theory of first-order coherence for statistically nonstationary light in the space-frequency domain.

Lahiri, Mayukh [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Wolf, Emil [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Institute of Optics, University of Rochester, Rochester, New York 14627 (United States)

2010-10-15T23:59:59.000Z

106

A Geometric Hamilton-Jacobi Theory for Classical Field Theories  

E-Print Network [OSTI]

In this paper we extend the geometric formalism of the Hamilton-Jacobi theory for hamiltonian mechanics to the case of classical field theories in the framework of multisymplectic geometry and Ehresmann connections.

M. de Leon; J. C. Marrero; D. Martin de Diego

2008-01-08T23:59:59.000Z

107

Quantum Cellular Automaton Theory of Light  

E-Print Network [OSTI]

We present a quantum theory of light based on quantum cellular automata (QCA). This approach allows us to have a thorough quantum theory of free electrodynamics encompassing an hypothetical discrete Planck scale. The theory is particularly relevant because it provides predictions at the macroscopic scale that can be experimentally tested. We show how, in the limit of small wave-vector k, the free Maxwell's equations emerge from two Weyl QCAs derived from informational principles in Ref. [1]. Within this framework the photon is introduced as a composite particle made of a pair of correlated massless Fermions, and the usual Bosonic statistics is recovered in the low photon density limit. We derive the main phenomenological features of the theory, consisting in dispersive propagation in vacuum, the occurrence of a small longitudinal polarization, and a saturation effect originated by the Fermionic nature of the photon. We then discuss whether these effects can be experimentally tested, and observe that only the dispersive effects are accessible with current technology, from observations of arrival times of pulses originated at cosmological distances.

Alessandro Bisio; Giacomo Mauro D'Ariano; Paolo Perinotti

2014-07-25T23:59:59.000Z

108

Baryon masses in the three-state Potts field theory in a weak magnetic field  

E-Print Network [OSTI]

The 3-state Potts field theory describes the scaling limit of the 3-state Potts model on the two-dimensional lattice near its continuous phase transition point. In the presence of thermal and magnetic field perturbations, the 3-state Potts field theory in the ordered phase exhibits confinement of kinks, which allows both mesons and baryons. We calculate the masses of light baryons in this model in the weak confinement regime in leading order of the small magnetic field. In leading order of perturbation theory, the light baryons can be viewed as bound states of three quantum particles - the kinks, which move on a line and interact via a linear potential. We determine the masses of the lightest baryons by numerical solution of the associated non-relativistic one-dimensional quantum three-body problem.

S. B. Rutkevich

2014-08-08T23:59:59.000Z

109

Mathematical Structure of Quantum Decision Theory  

E-Print Network [OSTI]

One of the most complex systems is the human brain whose formalized functioning is characterized by decision theory. We present a "Quantum Decision Theory" of decision making, based on the mathematical theory of separable Hilbert spaces. This mathematical structure captures the effect of superposition of composite prospects, including many incorporated intentions, which allows us to explain a variety of interesting fallacies and anomalies that have been reported to particularize the decision making of real human beings. The theory describes entangled decision making, non-commutativity of subsequent decisions, and intention interference of composite prospects. We demonstrate how the violation of the Savage's sure-thing principle (disjunction effect) can be explained as a result of the interference of intentions, when making decisions under uncertainty. The conjunction fallacy is also explained by the presence of the interference terms. We demonstrate that all known anomalies and paradoxes, documented in the context of classical decision theory, are reducible to just a few mathematical archetypes, all of which finding straightforward explanations in the frame of the developed quantum approach.

V. I. Yukalov; D. Sornette

2008-08-01T23:59:59.000Z

110

Quantum Tetrahedra  

E-Print Network [OSTI]

We discuss in details the role of Wigner 6j symbol as the basic building block unifying such different fields as state sum models for quantum geometry, topological quantum field theory, statistical lattice models and quantum computing. The apparent twofold nature of the 6j symbol displayed in quantum field theory and quantum computing -a quantum tetrahedron and a computational gate- is shown to merge together in a unified quantum-computational SU(2)-state sum framework.

Mauro Carfora; Annalisa Marzuoli; Mario Rasetti

2010-01-25T23:59:59.000Z

111

A quantum theory of distance along a curve  

E-Print Network [OSTI]

We present a quantum theory of distances along a curve, based on a linear line element that is equal to the operator square root of the quadratic metric of Riemannian geometry. Since the linear line element is an operator, we treat it according to the rules of quantum mechanics and interpret its eigenvalues as physically observable distances; the distance eigenvalues are naturally quantized. There are both positive and negative eigenvalues, which requires interpretation. Multi-element curves are defined as direct sums of line elements, and behave much like systems of spin half electrons in a magnetic field. For a curve of many elements an entropy and energy and temperature are quite naturally defined, leading via standard statistical thermodynamics to a relation between the most probable curve length and temperature. That relation may be viewed as a universal heat-shrinking property of curves. At this stage of the theory we do not include bodies or particles in the mix, do not suggest field equations for the quantum geometry, and questions of interpretation remain. The theory might conceivably be testable using observations of the early Universe, when the temperature of space was presumably quite high. In particular cosmogenesis may be thought of as time stopping at an infinite temperature as we go backwards in time to the beginning.

Ronald J. Adler

2014-02-13T23:59:59.000Z

112

The Theory of Quantized Fields. I  

Science Journals Connector (OSTI)

The conventional correspondence basis for quantum dynamics is here replaced by a self-contained quantum dynamical principle from which the equations of motion and the commutation relations can be deduced. The theory is developed in terms of the model supplied by localizable fields. A short review is first presented of the general quantum-mechanical scheme of operators and eigenvectors, in which emphasis is placed on the differential characterization of representatives and transformation functions by means of infinitesimal unitary transformations. The fundamental dynamical principle is stated as a variational equation for the transformation function connecting eigenvectors associated with different spacelike surfaces, which describes the temporal development of the system. The generator of the infinitesimal transformation is the variation of the action integral operator, the spacetime volume integral of the invariant lagrange function operator. The invariance of the lagrange function preserves the form of the dynamical principle under coordinate transformations, with the exception of those transformations which include a reversal in the positive sense of time, where a separate discussion is necessary. It will be shown in Sec. III that the requirement of invariance under time reflection imposes a restriction upon the operator properties of fields, which is simply the connection between the spin and statistics of particles. For a given dynamical system, changes in the transformation function arise only from alterations of the eigenvectors associated with the two surfaces, as generated by operators constructed from field variables attached to those surfaces. This yields the operator principle of stationary action, from which the equations of motion are obtained. Commutation relations are derived from the generating operator associated with a given surface. In particular, canonical commutation relations are obtained for those field components that are not restricted by equations of constraint. The surface generating operator also leads to generalized Schrdinger equations for the representative of an arbitrary state. Action integral variations which correspond to changing the dynamical system are discussed briefly. A method for constructing the transformation function is described, in a form appropriate to an integral spin field, which involves solving Hamilton-Jacobi equations for ordered operators. In Sec. III, the exceptional nature of time reflection is indicated by the remark that the charge and the energy-momentum vector behave as a pseudoscalar and pseudovector, respectively, for time reflection transformations. This shows, incidentally, that positive and negative charge must occur symmetrically in a completely covariant theory. The contrast between the pseudo energy-momentum vector and the proper displacement vector then indicates that time reflection cannot be described within the unitary transformation framework. This appears most fundamentally in the basic dynamical principle. It is important to recognize here that the contributions to the lagrange function of half-integral spin fields behave like pseudoscalars with respect to time reflection. The non-unitary transformation required to represent time reflection is found to be the replacement of a state vector by its dual, or complex conjugate vector, together with the transposition of all operators. The fundamental dynamical principle is then invariant under time reflection if inverting the order of all operators in the lagrange function leaves an integral spin contribution unaltered, and reverses the sign of a half-integral spin contribution. This implies the essential commutativity, or anti-commutativity, of integral and half-integral field components, respectively, which is the connection between spin and statistics.

Julian Schwinger

1951-06-15T23:59:59.000Z

113

Cancellation of anomalies in a path integral formulation for classical field theories  

E-Print Network [OSTI]

Some symmetries can be broken in the quantization process (anomalies) and this breaking is signalled by a non-invariance of the quantum path integral measure. In this talk we show that it is possible to formulate also classical field theories via path integral techniques. The associated classical functional measure is larger than the quantum one, because it includes some auxiliary fields. For a fermion coupled with a gauge field we prove that the way these auxiliary fields transform compensates exactly the Jacobian which arises from the transformation of the fields appearing in the quantum measure. This cancels the quantum anomaly and restores the symmetry at the classical level.

D. Mauro

2005-07-07T23:59:59.000Z

114

Scalar Field Quantum Inequalities in Static Spacetimes  

E-Print Network [OSTI]

We discuss quantum inequalities for minimally coupled scalar fields in static spacetimes. These are inequalities which place limits on the magnitude and duration of negative energy densities. We derive a general expression for the quantum inequality for a static observer in terms of a Euclidean two-point function. In a short sampling time limit, the quantum inequality can be written as the flat space form plus subdominant correction terms dependent upon the geometric properties of the spacetime. This supports the use of flat space quantum inequalities to constrain negative energy effects in curved spacetime. Using the exact Euclidean two-point function method, we develop the quantum inequalities for perfectly reflecting planar mirrors in flat spacetime. We then look at the quantum inequalities in static de~Sitter spacetime, Rindler spacetime and two- and four-dimensional black holes. In the case of a four-dimensional Schwarzschild black hole, explicit forms of the inequality are found for static observers nea...

Pfenning, M J; Pfenning, Michael J.

1998-01-01T23:59:59.000Z

115

Quantum fields with noncommutative target spaces  

Science Journals Connector (OSTI)

Quantum field theories (QFTs) on noncommutative spacetimes are currently under intensive study. Usually such theories have world sheet noncommutativity. In the present work, instead, we study QFTs with commutative world sheet and noncommutative target space. Such noncommutativity can be interpreted in terms of twisted statistics and is related to earlier work of Oeckl [R. Oeckl, Commun. Math. Phys. 217, 451 (2001).], and others [A.?P. Balachandran, G. Mangano, A. Pinzul, and S. Vaidya, Int. J. Mod. Phys. A 21, 3111 (2006); A.?P. Balachandran, A. Pinzul, and B.?A. Qureshi, Phys. Lett. B 634, 434 (2006); A.?P. Balachandran, A. Pinzul, B.?A. Qureshi, and S. Vaidya, arXiv:hep-th/0608138; A.?P. Balachandran, T.?R. Govindarajan, G. Mangano, A. Pinzul, B.?A. Qureshi, and S. Vaidya, Phys. Rev. D 75, 045009 (2007); A. Pinzul, Int. J. Mod. Phys. A 20, 6268 (2005); G. Fiore and J. Wess, Phys. Rev. D 75, 105022 (2007); Y. Sasai and N. Sasakura, Prog. Theor. Phys. 118, 785 (2007)]. The twisted spectra of their free Hamiltonians has been found earlier by Carmona etal. [J.?M. Carmona, J.?L. Cortes, J. Gamboa, and F. Mendez, Phys. Lett. B 565, 222 (2003); J.?M. Carmona, J.?L. Cortes, J. Gamboa, and F. Mendez, J. High Energy Phys. 03 (2003) 058]. We review their derivation and then compute the partition function of one such typical theory. It leads to a deformed blackbody spectrum, which is analyzed in detail. The difference between the usual and the deformed blackbody spectrum appears in the region of high frequencies. Therefore we expect that the deformed blackbody radiation may potentially be used to compute a Greisen-Zatsepin-Kuzmin cutoff which will depend on the noncommutative parameter ?.

A. P. Balachandran; A. R. Queiroz; A. M. Marques; P. Teotonio-Sobrinho

2008-05-30T23:59:59.000Z

116

Symmetries and Renormalization of Noncommutative Field Theory  

SciTech Connect (OSTI)

An overview of recent developments in the renormalization and in the implementation of spacetime symmetries of noncommutative field theory is presented, and argued to be intimately related.

Szabo, Richard J. [Department of Mathematics, Heriot-Watt University, Colin Maclaurin Building, Riccarton, Edinburgh EH14 4AS (United Kingdom); Maxwell Institute for Mathematical Sciences, Heriot-Watt University, Colin Maclaurin Building, Riccarton, Edinburgh EH14 4AS (United Kingdom)

2007-06-19T23:59:59.000Z

117

Can we see gravitational collapse in (quantum) gravity perturbation theory?  

E-Print Network [OSTI]

In this paper, by making use of the perturbative expansion around topological field theory we are trying to understand why the standard perturbation theory for General Relativity, which starts with linearized gravity does not see gravitational collapse. We start with investigating classical equations of motion. For zero Immirzi parameter the ambiguity of the standard perturbative expansion is reproduced. This ambiguity is related to the appearance of the linearized diffeomorphism symmetry, which becomes unlinked from the original diffeomorphism symmetry. Introducing Immirzi parameter makes it possible to restore the link between these two symmetries and thus removes the ambiguity, but at the cost of making classical perturbation theory rather intractable. Then we argue that the two main sources of complexity of perturbation theory, infinite number of degrees of freedom and non-trivial curvature of the phase space of General Relativity could be disentangled when studying {\\it quantum} amplitudes. As an illustration we consider zero order approximation in quantum perturbation theory. We identify relevant observables, and sketch their quantization. We find some indications that this zero order approximation might be described by Doubly Special Relativity.

J. Kowalski-Glikman; A. Starodubtsev

2006-12-14T23:59:59.000Z

118

Detailed discussions and calculations of quantum Regge calculus of Einstein-Cartan theory  

Science Journals Connector (OSTI)

This article presents detailed discussions and calculations of the recent paper Quantum Regge calculus of Einstein-Cartan theory in 9. The Euclidean space-time is discretized by a four-dimensional simplicial complex. We adopt basic tetrad and spin-connection fields to describe the simplicial complex. By introducing diffeomorphism and local Lorentz invariant holonomy fields, we construct a regularized Einstein-Cartan theory for studying the quantum dynamics of the simplicial complex and fermion fields. This regularized Einstein-Cartan action is shown to properly approach to its continuum counterpart in the continuum limit. Based on the local Lorentz invariance, we derive the dynamical equations satisfied by invariant holonomy fields. In the mean-field approximation, we show that the averaged size of 4-simplex, the element of the simplicial complex, is larger than the Planck length. This formulation provides a theoretical framework for analytical calculations and numerical simulations to study the quantum Einstein-Cartan theory.

She-Sheng Xue

2010-09-30T23:59:59.000Z

119

A Foundation Theory of Quantum Mechanics  

E-Print Network [OSTI]

The nRules are empirical regularities that were discovered in macroscopic situations where the outcome is known. When they are projected theoretically into the microscopic domain they predict a novel ontology including the frequent collapse of an atomic wave function, thereby defining an nRule based foundation theory. Future experiments can potentially discriminate between this and other foundation theories of (non-relativistic) quantum mechanics. Important features of the nRules are: (1) they introduce probability through probability current rather than the Born rule, (2) they are valid independent of size (micro or macroscopic), (3) they apply to individual trials, not just to ensembles of trials. (4) they allow all observers to be continuously included in the system without ambiguity, (5) they account for the collapse of the wave function without introducing new or using old physical constants, and (6) in dense environments they provide a high frequency of stochastic localizations of quantum mechanical objects. Key words: measurement, stochastic choice, state reduction.

Richard A Mould

2006-07-10T23:59:59.000Z

120

Scalar Field Quantum Inequalities in Static Spacetimes  

E-Print Network [OSTI]

We discuss quantum inequalities for minimally coupled scalar fields in static spacetimes. These are inequalities which place limits on the magnitude and duration of negative energy densities. We derive a general expression for the quantum inequality for a static observer in terms of a Euclidean two-point function. In a short sampling time limit, the quantum inequality can be written as the flat space form plus subdominant correction terms dependent upon the geometric properties of the spacetime. This supports the use of flat space quantum inequalities to constrain negative energy effects in curved spacetime. Using the exact Euclidean two-point function method, we develop the quantum inequalities for perfectly reflecting planar mirrors in flat spacetime. We then look at the quantum inequalities in static de~Sitter spacetime, Rindler spacetime and two- and four-dimensional black holes. In the case of a four-dimensional Schwarzschild black hole, explicit forms of the inequality are found for static observers near the horizon and at large distances. It is show that there is a quantum averaged weak energy condition (QAWEC), which states that the energy density averaged over the entire worldline of a static observer is bounded below by the vacuum energy of the spacetime. In particular, for an observer at a fixed radial distance away from a black hole, the QAWEC says that the averaged energy density can never be less than the Boulware vacuum energy density.

Michael J. Pfenning; L. H. Ford

1997-10-09T23:59:59.000Z

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121

N=2 gauge theories and degenerate fields of Toda theory  

SciTech Connect (OSTI)

We discuss the correspondence between degenerate fields of the W{sub N} algebra and punctures of Gaiotto's description of the Seiberg-Witten curve of N=2 superconformal gauge theories. Namely, we find that the type of degenerate fields of the W{sub N} algebra, with null states at level one, is classified by Young diagrams with N boxes, and that the singular behavior of the Seiberg-Witten curve near the puncture agrees with that of W{sub N} generators. We also find how to translate mass parameters of the gauge theory to the momenta of the Toda theory.

Kanno, Shoichi; Matsuo, Yutaka; Shiba, Shotaro [Department of Physics, Faculty of Science, University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Tachikawa, Yuji [School of Natural Sciences, Institute for Advanced Study, Princeton, New Jersey 08540 (United States)

2010-02-15T23:59:59.000Z

122

Heavy quarks in effective field theories  

E-Print Network [OSTI]

Heavy quark physics serves as a probe to understand QCD, measure standard model parameters, and look for signs of new physics. We study several aspects of heavy quark systems in an effective field theory framework, including ...

Jain, Ambar

2009-01-01T23:59:59.000Z

123

DENSITY FUNCTIONAL THEORY OF FIELD THEORETICAL SYSTEMS  

E-Print Network [OSTI]

DENSITY FUNCTIONAL THEORY OF FIELD THEORETICAL SYSTEMS E. Engel Inst. fur Theor. Physik background of relativistic density functional theory is emphasized and its consequences for relativistic Kohn-Sham equations are shown. The local density approximation for the exchange energy functional is reviewed

Engel, Eberhard

124

Field Theory of Matter. IV  

Science Journals Connector (OSTI)

The relativistic dynamics of 0- and 1- mesons in the idealization of U3 symmetry is derived from the hypothesis that a compact group of transformations on fundamental fields induces a predominantly local and linear transformation of the phenomenological fields that are associated with particles. The physical picture of phenomenological fields as highly localized functions of fundamental fields implies that the interaction term of the phenomenological Lagrange function can have symmetry properties, expressed by invariance under the compact transformation group, that have no significance for the remainder of the Lagrange function, which describes the propagation of the physical excitations. It is verified that the meson interaction term derived by considering fundamental fermion fields is invariant under the parity-conserving group U6U6. The implied connection between the ??? and ??? coupling constants is well satisfied. There is a brief discussion of the dynamics of fermion-particle triplets, from which it is shown that the invariance of the similarly derived interaction term implies the mass degeneracy of the singlet and octuplet of 1- mesons, without relation to 0- masses. The triplets are also used to illustrate the derivation of gauge- and relativistically invariant electromagnetic properties. The mass degeneracy of the nine 1- mesons, and of nine 2+ mesons, can be inferred from the commutation properties of bilinear combinations of the fundamental field.

Julian Schwinger

1965-10-11T23:59:59.000Z

125

Quantum decoherence in the theory of open systems  

E-Print Network [OSTI]

In the framework of the Lindblad theory for open quantum systems, we determine the degree of quantum decoherence of a harmonic oscillator interacting with a thermal bath. It is found that the system manifests a quantum decoherence which is more and more significant in time. We calculate also the decoherence time scale and analyze the transition from quantum to classical behaviour of the considered system.

A. Isar

2007-04-25T23:59:59.000Z

126

The Theory of Quantized Fields. II  

Science Journals Connector (OSTI)

The arguments leading to the formulation of the action principle for a general field are presented. In association with the complete reduction of all numerical matrices into symmetrical and antisymmetrical parts, the general field is decomposed into two sets, which are identified with Bose-Einstein and Fermi-Dirac fields. The spin restriction on the two kinds of fields is inferred from the time reflection invariance requirement. The consistency of the theory is verified in terms of a criterion involving the various generators of infinitesimal transformations. Following a discussion of charged fields, the electromagnetic field is introduced to satisfy the postulate of general gauge invariance. As an aspect of the latter, it is recognized that the electromagnetic field and charged fields are not kinematically independent. After a discussion of the field strength commutation relations, the independent dynamical variables of the electromagnetic field are exhibited in terms of a special gauge.

Julian Schwinger

1953-08-01T23:59:59.000Z

127

Quantum fields on closed timelike curves  

SciTech Connect (OSTI)

Recently, there has been much interest in the evolution of quantum particles on closed timelike curves (CTCs). However, such models typically assume pointlike particles with only two degrees of freedom; a very questionable assumption given the relativistic setting of the problem. We show that it is possible to generalize the Deutsch model of CTCs to fields using the equivalent circuit formalism. We give examples for coherent, squeezed, and single-photon states interacting with the CTC via a beamsplitter. The model is then generalized further to account for the smooth transition to normal quantum mechanics as the CTC becomes much smaller than the size of the modes interacting on it. In this limit, we find that the system behaves like a standard quantum-mechanical feedback loop.

Pienaar, J. L.; Myers, C. R.; Ralph, T. C. [School of Mathematics and Physics, The University of Queensland, Brisbane 4072, Queensland (Australia)

2011-12-15T23:59:59.000Z

128

The Vector Meson Mass in Chiral Effective Field Theory  

E-Print Network [OSTI]

A brief overview of Quantum Chromodynamics (QCD) as a non-Abelian gauge field theory, including symmetries and formalism of interest, will precede a focused discussion on the use of an Effective Field Theory (EFT) as a low energy perturbative expansion technique. Regularization schemes involved in Chiral Perturbation Theory (\\c{hi}PT) will be reviewed and compared with EFT. Lattices will be discussed as a useful procedure for studying large mass particles. An Effective Field Theory will be formulated, and the self energy of the \\r{ho} meson for a Finite-Range Regulated (FRR) theory will be calculated. This will be performed in both full QCD and the simpler quenched approximation (QQCD). Finite-volume artefacts, due to the finite box size on the lattice, will be quantified. Currently known lattice results will be used to calculate the \\r{ho} meson mass, and the possibility of unquenching will be explored. The aim of the research was to determine whether a stable unquenching procedure for the \\r{ho} meson could be discovered. The results from the original research indicate that there is no such procedure because the \\r{ho} mesons are unstable. Unless additional data involving lighter quark masses is available, an element of modelling is needed for successful unquenching.

Jonathan M M Hall

2014-05-01T23:59:59.000Z

129

Construction of relativistic quantum theory: a progress report  

SciTech Connect (OSTI)

We construct the particulate states of quantum physics using a recursive computer program that incorporates non-determinism by means of locally arbitrary choices. Quantum numbers and coupling constants arise from the construction via the unique 4-level combinatorial hierarchy. The construction defines indivisible quantum events with the requisite supraluminal correlations, yet does not allow supraluminal communication. Measurement criteria incorporate c, h-bar and m/sub p/ or (not ''and'') G, connected to laboratory events via finite particle number scattering theory and the counter paradigm. The resulting theory is discrete throughout, contains no infinities, and, as far as we have developed it, is in agreement with quantum mechanical and cosmological fact.

Noyes, H.P.

1986-06-01T23:59:59.000Z

130

Qubit-Programmable Operations on Quantum Light Fields  

E-Print Network [OSTI]

Engineering quantum operations is one of the main abilities we need for developing quantum technologies and designing new fundamental tests. Here we propose a scheme for realising a controlled operation acting on a travelling quantum field, whose functioning is determined by an input qubit. This study introduces new concepts and methods in the interface of continuous- and discrete-variable quantum optical systems.

Marco Barbieri; Nicol Spagnolo; Franck Ferreyrol; Rmi Blandino; Brian J. Smith; Rosa Tualle-Brouri

2014-12-01T23:59:59.000Z

131

A CSP Field Theory with Helicity Correspondence  

E-Print Network [OSTI]

We propose the first covariant local action describing the propagation of a single free continuous-spin degree of freedom. The theory is simply formulated as a gauge theory in a "vector superspace", but can also be formulated in terms of a tower of symmetric tensor gauge fields. When the spin invariant $\\rho$ vanishes, the helicity correspondence is manifest -- familiar gauge theory actions are recovered and couplings to conserved currents can easily be introduced. For non-zero $\\rho$, a tower of tensor currents must be present, of which only the lowest rank is exactly conserved. A paucity of local gauge-invariant operators for non-zero $\\rho$ suggests that the equations of motion in any interacting theory should be covariant, not invariant, under a generalization of the free theory's gauge symmetry.

Schuster, Philip

2014-01-01T23:59:59.000Z

132

A CSP Field Theory with Helicity Correspondence  

E-Print Network [OSTI]

We propose the first covariant local action describing the propagation of a single free continuous-spin degree of freedom. The theory is simply formulated as a gauge theory in a "vector superspace", but can also be formulated in terms of a tower of symmetric tensor gauge fields. When the spin invariant $\\rho$ vanishes, the helicity correspondence is manifest -- familiar gauge theory actions are recovered and couplings to conserved currents can easily be introduced. For non-zero $\\rho$, a tower of tensor currents must be present, of which only the lowest rank is exactly conserved. A paucity of local gauge-invariant operators for non-zero $\\rho$ suggests that the equations of motion in any interacting theory should be covariant, not invariant, under a generalization of the free theory's gauge symmetry.

Philip Schuster; Natalia Toro

2014-04-02T23:59:59.000Z

133

The Inverse-Cube Central Force Field in Quantum Mechanics  

Science Journals Connector (OSTI)

The problem of the motion of a particle in an inverse-cube central force field is fully treated by quantum mechanics and the results compared with the classical theory. Taking the effective radial potential energy as Sr2, although the solutions for negative energy for 0?S?-h232?2? satisfy the usual boundary conditions, they can not be admitted because the Hamiltonian is not Hermitian in these solutions. This corresponds to taking (l+12)2 in place of l(l+1) as the analogue of the square of the classical angular momentum. If we do this, we get a complete analogy between the classical and quantum mechanically allowed solutions, with no quantization. The solutions involve Bessel functions of both real and imaginary orders with both real and imaginary arguments.

George H. Shortley

1931-07-01T23:59:59.000Z

134

Completely Reducible maps in Quantum Information Theory  

E-Print Network [OSTI]

In order to compute the Schmidt decomposition of $A\\in M_k\\otimes M_m$, we must consider an associated self-adjoint map. Here, we show that if $A$ is positive under partial transposition (PPT) or symmetric with positive coefficients (SPC) or invariant under realignment then its associated self-adjoint map is completely reducible. We give applications of this fact in Quantum Information Theory. We recover some theorems recently proved for PPT and SPC matrices and we prove these theorems for matrices invariant under realignment using theorems of Perron-Frobenius theory. One consequence of these theorems is the fact that if $\\mathbb{C}^{k}$ contains $k$ mutually unbiased bases then $\\mathbb{C}^{k}$ contains $k+1$. We search for other types of matrices that could have the same property. We consider a group of linear transformations acting on $M_k\\otimes M_k$, which contains the partial transpositions and the realignment map. For each element of this group, we consider the set of matrices in $M_k\\otimes M_k\\simeq M_{k^2}$ that are positive and remain positive, or invariant, under the action of this element. Within this family of sets, we have the set of PPT matrices, the set of SPC matrices and the set of matrices invariant under realignment. We show that these three sets are the only sets of this family such that the associated self-adjoint map of each matrix is completely reducible. We also show that every matrix invariant under realignment is PPT in $M_2\\otimes M_2$ and we present a counterexample in $M_k\\otimes M_k$, $k\\geq 3$.

Daniel Cariello

2014-12-12T23:59:59.000Z

135

Time Evolution in the external field problem of Quantum Electrodynamics  

E-Print Network [OSTI]

A general problem of quantum field theories is the fact that the free vacuum and the vacuum for an interacting theory belong to different, non-equivalent representations of the canonical (anti-)commutation relations. In the external field problem of QED, we encounter this problem in the form that the Dirac time evolution for an external field with non-vanishing magnetic components will not satisfy the Shale-Stinespring condition, known to be necessary and sufficient for the existence of an implementation on the fermionic Fock space. Therefore, a second quantization of the time evolution in the usual way is impossible. In this thesis, we present several rigorous approaches to QED with time-dependent, external fields and analyze in what sense a time evolution can exist in the second quantized theory. We study different constructions of the fermionic Fock space and prove their equivalence. We study and compare the results of Deckert et. al. (2010), where the time evolution is realized as unitary transformations ...

Lazarovici, Dustin

2013-01-01T23:59:59.000Z

136

The affine gauge theory in the quantum phase space CP(N-1)  

E-Print Network [OSTI]

In the present article I propose a non-linear relativistic 4-d field model originated by the internal dynamics in CP(N-1). There is no initially distinction between `particle' and `field', and the space-time manifold is derivable. The main idea is to base the theory on the relative amplitudes solely. Quantum measurements will be described in terms of the parallel transport of the local dynamical variables and a specific gauge reduction of the full state vector to the Qubit coherent state. I will discuss here field equations of quantum particle arising in the dynamical space-time.

Peter Leifer

2005-03-19T23:59:59.000Z

137

A quantum cascade laser in a transverse magnetic field. A model of the open triple-barrier active region  

Science Journals Connector (OSTI)

A theory of spectral parameters and active dynamic conductivity of the quantum cascade laser is proposed in the model of a triple-barrier active region of an individual cascade in a transverse magnetic field. In ...

N. V. Tkach; I. V. Boyko; Ju. A. Seti; G. G. Zegrya

2013-06-01T23:59:59.000Z

138

Markov states of the quantum electromagnetic field  

Science Journals Connector (OSTI)

A translation-invariant state (a quantum Markov chain) is associated with a nearest-neighbor interaction on a one-dimensional lattice by a new technique which provides closed forms for all the correlation functions. When applied to an Ising-type perturbation of a chain of harmonic oscillators, the dynamics can be computed explicitly. The resulting translation-invariant distribution is substantially different from the Planck distribution when the temperature and the coupling constant are large. For the evolution of the field operators on a given mode, we obtain a natural nonlinear generalization of the theorem which states that the free evolution of the field operators is obtained by second quantization of the classical free evolution.

Luigi Accardi and Geoffrey S. Watson

1987-02-01T23:59:59.000Z

139

Maps for general open quantum systems and a theory of linear quantum error correction  

E-Print Network [OSTI]

We show that quantum subdynamics of an open quantum system can always be described by a Hermitian map, irrespective of the form of the initial total system state. Since the theory of quantum error correction was developed based on the assumption of completely positive (CP) maps, we present a generalized theory of linear quantum error correction, which applies to any linear map describing the open system evolution. In the physically relevant setting of Hermitian maps, we show that the CP-map based version of quantum error correction theory applies without modifications. However, we show that a more general scenario is also possible, where the recovery map is Hermitian but not CP. Since non-CP maps have non-positive matrices in their range, we provide a geometric characterization of the positivity domain of general linear maps. In particular, we show that this domain is convex, and that this implies a simple algorithm for finding its boundary.

A. Shabani; D. A. Lidar

2009-02-14T23:59:59.000Z

140

Nuclear effective field theory on the lattice  

E-Print Network [OSTI]

In the low-energy region far below the chiral symmetry breaking scale (which is of the order of 1 GeV) chiral perturbation theory provides a model-independent approach for quantitative description of nuclear processes. In the two- and more-nucleon sector perturbation theory is applicable only at the level of an effective potential which serves as input in the corresponding dynamical equation. To deal with the resulting many-body problem we put chiral effective field theory (EFT) on the lattice. Here we present the results of our lattice EFT study up to next-to-next-to-leading order in the chiral expansion. Accurate description of two-nucleon phase-shifts and ground state energy ratio of dilute neutron matter up to corrections of higher orders shows that lattice EFT is a promising tool for a quantitative description of low-energy few- and many-body systems.

Hermann Krebs; Bugra Borasoy; Evgeny Epelbaum; Dean Lee; Ulf-G. Mei ner

2008-10-01T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


141

Graphene as a Lattice Field Theory  

E-Print Network [OSTI]

We introduce effective field theories for the electronic properties of graphene in terms of relativistic fermions propagating in 2+1 dimensions, and outline how strong inter-electron interactions may be modelled by numerical simulation of a lattice field theory. For strong enough coupling an insulating state can form via condensation of particle-hole pairs, and it is demonstrated that this is a theoretical possibility for monolayer graphene. For bilayer graphene the effect of an interlayer bias voltage can be modelled by the introduction of a chemical potential (akin to isopsin chemical potential in QCD) with no accompanying sign problem; simulations reveal the presence of strong interactions among the residual degrees of freedom at the resulting Fermi surface, which is disrupted by an excitonic condensate. We also present preliminary results for the quasiparticle dispersion, which permit direct estimates of both the Fermi momentum and the induced gap.

Simon Hands; Wes Armour; Costas Strouthos

2015-01-08T23:59:59.000Z

142

Graphene as a Lattice Field Theory  

E-Print Network [OSTI]

We introduce effective field theories for the electronic properties of graphene in terms of relativistic fermions propagating in 2+1 dimensions, and outline how strong inter-electron interactions may be modelled by numerical simulation of a lattice field theory. For strong enough coupling an insulating state can form via condensation of particle-hole pairs, and it is demonstrated that this is a theoretical possibility for monolayer graphene. For bilayer graphene the effect of an interlayer bias voltage can be modelled by the introduction of a chemical potential (akin to isopsin chemical potential in QCD) with no accompanying sign problem; simulations reveal the presence of strong interactions among the residual degrees of freedom at the resulting Fermi surface, which is disrupted by an excitonic condensate. We also present preliminary results for the quasiparticle dispersion, which permit direct estimates of both the Fermi momentum and the induced gap.

Hands, Simon; Strouthos, Costas

2015-01-01T23:59:59.000Z

143

Wonderful Compactifications in Quantum Field Theory  

E-Print Network [OSTI]

This article reviews the use of DeConcini-Procesi wonderful models in renormalization of ultraviolet divergences in position space as introduced by Bergbauer, Brunetti and Kreimer. In contrast to the exposition there we employ a slightly different approach; instead of the subspaces in the arrangement of divergent loci, we use the poset of divergent subgraphs as the main tool to describe the whole renormalization process. This is based on an article by Feichtner, where wonderful models were studied from a purely combinatorial viewpoint. The main motivation for this approach is the fact that both, renormalization and the model construction, are governed by the combinatorics of this poset. Not only simplifies this the exposition considerably, but also allows to study the renormalization operators in more detail. Moreover, we explore the renormalization group in this setting by studying how the renormalized distributions behave under a change of renormalization points.

Marko Berghoff

2015-02-02T23:59:59.000Z

144

High-Frequency Conductivity of Quantum Plasma in a Magnetic Field  

Science Journals Connector (OSTI)

The problem of the electromagnetic absorption coefficient in a quantum plasma in the presence of a uniform magnetic field is investigated by a kinetic description. The finite duration of encounters is taken into account in a self-consistent fashion which includes collective effects properly. This treatment is the quantum extension of an earlier classical study. The application of this theory to heavily doped semiconductors is suggested.

Carl Oberman and Amiram Ron

1963-05-15T23:59:59.000Z

145

Scalar Field Theories with Polynomial Shift Symmetries  

E-Print Network [OSTI]

We continue our study of naturalness in nonrelativistic QFTs of the Lifshitz type, focusing on scalar fields that can play the role of Nambu-Goldstone (NG) modes associated with spontaneous symmetry breaking. Such systems allow for an extension of the constant shift symmetry to a shift by a polynomial of degree $P$ in spatial coordinates. These "polynomial shift symmetries" in turn protect the technical naturalness of modes with a higher-order dispersion relation, and lead to a refinement of the proposed classification of infrared Gaussian fixed points available to describe NG modes in nonrelativistic theories. Generic interactions in such theories break the polynomial shift symmetry explicitly to the constant shift. It is thus natural to ask: Given a Gaussian fixed point with polynomial shift symmetry of degree $P$, what are the lowest-dimension operators that preserve this symmetry, and deform the theory into a self-interacting scalar field theory with the shift symmetry of degree $P$? To answer this (essen...

Griffin, Tom; Horava, Petr; Yan, Ziqi

2014-01-01T23:59:59.000Z

146

Working Group Report: Lattice Field Theory  

SciTech Connect (OSTI)

This is the report of the Computing Frontier working group on Lattice Field Theory prepared for the proceedings of the 2013 Community Summer Study ("Snowmass"). We present the future computing needs and plans of the U.S. lattice gauge theory community and argue that continued support of the U.S. (and worldwide) lattice-QCD effort is essential to fully capitalize on the enormous investment in the high-energy physics experimental program. We first summarize the dramatic progress of numerical lattice-QCD simulations in the past decade, with some emphasis on calculations carried out under the auspices of the U.S. Lattice-QCD Collaboration, and describe a broad program of lattice-QCD calculations that will be relevant for future experiments at the intensity and energy frontiers. We then present details of the computational hardware and software resources needed to undertake these calculations.

Blum, T.; et al.,

2013-10-22T23:59:59.000Z

147

Lattice field theory simulations of graphene  

E-Print Network [OSTI]

We discuss the Monte Carlo method of simulating lattice field theories as a means of studying the low-energy effective theory of graphene. We also report on simulational results obtained using the Metropolis and Hybrid Monte Carlo methods for the chiral condensate, which is the order parameter for the semimetal-insulator transition in graphene, induced by the Coulomb interaction between the massless electronic quasiparticles. The critical coupling and the associated exponents of this transition are determined by means of the logarithmic derivative of the chiral condensate and an equation-of-state analysis. A thorough discussion of finite-size effects is given, along with several tests of our calculational framework. These results strengthen the case for an insulating phase in suspended graphene, and indicate that the semimetal-insulator transition is likely to be of second order, though exhibiting neither classical critical exponents, nor the predicted phenomenon of Miransky scaling.

Joaqun E. Drut; Timo A. Lhde

2009-01-06T23:59:59.000Z

148

Quantum kinetic theory with nonlocal coherence  

E-Print Network [OSTI]

In this thesis we develop a novel approximation scheme (eQPA), where the effects of nonlocal coherence are included in the kinetic approach to nonequilibrium quantum dynamics. The key element in our formalism is the finding of new singular shell solutions, located at $k_{0,z} = 0$ in the phase space of 2-point Wightman function, which describe the nonlocal quantum coherence between the ``opposite'' mass-shell excitations for spatially homogeneous and static planar symmetric problems, respectively. This phase space structure leads to a closed set of transport equations for the corresponding on-shell distribution functions $f$, providing an extension to the standard quantum Boltzmann equation. We have considered a number of applications to demonstrate the use of our formalism, including the Klein problem, quantum reflection from a CP-violating mass wall and coherent production of (fermionic and scalar) particles in an oscillating background. Our formalism should be of relevance for many problems in particle physics and cosmology, including baryogenesis and neutrino flavour oscillations in an inhomogeneous background.

Matti Herranen

2009-06-17T23:59:59.000Z

149

Quantum theory of nonequilibrium processes, 1  

SciTech Connect (OSTI)

Green's function techniques for studying nonequilibrium quantum processes are discussed. Perturbation expansions and Green's function equations of motion are developed for noncorrelated and correlated initial states of a system. A transition, from the Kadanoff-Baym Green's function equations of motion to the Boltzmann equation, and specifications of the respective limit, are examined in detail.

Danielewicz, P.

1984-02-01T23:59:59.000Z

150

Compact boson stars in K field theories  

E-Print Network [OSTI]

We study a scalar field theory with a non-standard kinetic term minimally coupled to gravity. We establish the existence of compact boson stars, that is, static solutions with compact support of the full system with self-gravitation taken into account. Concretely, there exist two types of solutions, namely compact balls on the one hand, and compact shells on the other hand. The compact balls have a naked singularity at the center. The inner boundary of the compact shells is singular, as well, but it is, at the same time, a Killing horizon. These singular, compact shells therefore resemble black holes.

C. Adam; N. Grandi; P. Klimas; J. Sanchez-Guillen; A. Wereszczynski

2009-09-16T23:59:59.000Z

151

Compact boson stars in K field theories  

E-Print Network [OSTI]

We study a scalar field theory with a non-standard kinetic term minimally coupled to gravity. We establish the existence of compact boson stars, that is, static solutions with compact support of the full system with self-gravitation taken into account. Concretely, there exist two types of solutions, namely compact balls on the one hand, and compact shells on the other hand. The compact balls have a naked singularity at the center. The inner boundary of the compact shells is singular, as well, but it is, at the same time, a Killing horizon. These singular, compact shells therefore resemble black holes.

Adam, C; Klimas, P; Snchez-Guilln, J; Wereszczynski, A

2009-01-01T23:59:59.000Z

152

Quantum critical benchmark for density functional theory  

E-Print Network [OSTI]

Two electrons at the threshold of ionization represent a severe test case for electronic structure theory. A pseudospectral method yields a very accurate density of the two-electron ion with nuclear charge close to the critical value. Highly accurate energy components and potentials of Kohn-Sham density functional theory are given, as well as a useful parametrization of the critical density. The challenges for density functional approximations and the strength of correlation are also discussed.

Paul E. Grabowski; Kieron Burke

2014-08-09T23:59:59.000Z

153

ETHTH/9926 ON A CLASSICAL LIMIT OF QUANTUM THEORY  

E-Print Network [OSTI]

--8093 Z¨urich, Switzerland 2 Courant Institute of Mathematical Sciences, New York University, 251 Mercer Street, New York, NY 10471, USA #12; On a Classical Limit of Quantum Theory . . . , 1 1 GeneralB and ~, and from the speed of light, c, and Newton's law of gravitational attraction he could then infer

154

Kinetic transport theory with quantum coherence  

E-Print Network [OSTI]

We derive transport equations for fermions and bosons in spatially or temporally varying backgrounds with special symmetries, by use of the Schwinger-Keldysh formalism. In a noninteracting theory the coherence information is shown to be encoded in new singular shells for the 2-point function. Imposing this phase space structure to the interacting theory leads to a a self-consistent equation of motion for a physcial density matrix, including coherence and a well defined collision integral. The method is applied e.g. to demonstrate how an initially coherent out-of-equlibrium state approaches equlibrium through decoherence and thermalization.

Matti Herranen; Kimmo Kainulainen; Pyry M. Rahkila

2008-11-06T23:59:59.000Z

155

From Quantum Mechanics to String Theory  

E-Print Network [OSTI]

electric fields to accelerate the particles and magnetic fields to control their directions detectors particles, the nuclear force) neutrinos (beta decay, conservation laws, particle stability) Thursday, May 7 these states exist, but they are all filled. Redefine the vacuum as this situation: define this as a zero

156

Quantum field theoretic properties of Lorentz-violating operators of nonrenormalizable dimension in the fermion sector  

E-Print Network [OSTI]

In the current paper the properties of a quantum field theory based on certain sets of Lorentz-violating coefficients in the nonminimal fermion sector of the Standard-Model Extension are analyzed. In particular, three families of coefficients are considered, where two of them are CPT-even and the third is CPT-odd. As a first step the modified fermion dispersion relations are obtained. Then the positive- and negative-energy solutions of the modified Dirac equation and the fermion propagator are derived. These are used to demonstrate the validity of the optical theorem at tree-level, which provides a cross-check for the results obtained. Furthermore unitarity is examined and seems to be valid for the first set of CPT-even coefficients. However for the remaining sets certain issues with unitarity are found. The article demonstrates that the adapted quantum field theoretical methods at tree-level work for the nonminimal, Lorentz-violating framework considered. Besides, the quantum field theory based on the first family of CPT-even coefficients is most likely well-behaved at lowest order perturbation theory. The results are important for future phenomenological investigations carried out in the context of field theory, e.g., the computation of decay rates and cross sections at tree-level.

M. Schreck

2014-09-04T23:59:59.000Z

157

Integrable Conformal Field Theory - A Case Study  

SciTech Connect (OSTI)

Over the last decades, 2-dimensional conformal field theory has been developed into a powerful tool that has been applied to problems in diverse branches of physics and mathematics. Models are usually solved algebraically by exploiting certain infinite dimensional symmetries. But the presence of sufficient world-sheet symmetry is a rather exceptional feature, one that is e.g. not present for curved string backgrounds at generic points in moduli space. In this note I review some recent work which aims at computing spectra of conformal sigma models without spectrum generating symmetries. Our main results are illustrated at the example of complex projective superspace (C) P{sup N-1|N}. This note is based on several publications with C. Candu, T. Creutzig, V. Mitev, T. Quella and H. Saleur.

Schomerus, Volker [DESY Hamburg, Theory Group, Notkestrasse 85, D-22607 Hamburg (Germany)

2010-06-17T23:59:59.000Z

158

The Theory of Quantized Fields. VI  

Science Journals Connector (OSTI)

This paper treats the effect of a time-independent external electromagnetic field upon a Dirac field by constructing the transformation function in a representation adapted to the external field. In addition to the alteration of the Green's function, the structure of the transformation function differs from that of the zero field situation by a factor which describes the energy of the modified vacuum state. A formula for the vacuum energy is obtained and expressed in a form appropriate to a localized field, in terms of the energy eigenvalues of discrete modes, and of the phase shifts associated with continuum modes. Determinantal methods are then introduced, and the class of fields is established for which a certain frequency-dependent modified determinant is an integral function of the parameter measuring the strength of the field. The properties of the determinant are investigated in the two frequency regions |p0|m, with regard to the zeros of the real determinant in the former region, which are the frequencies of the discrete modes, and to the phase of the complex determinant in the latter region. In the second situation, a connection is established with a unitary matrix defined for modes of a given frequency, and the phase of the determinant is expressed in terms of the eigenphases of this matrix. Following a discussion of the asymptotic behavior of the determinant as a function of p0, the modified determinant is constructed in terms of the discrete mode energies and of the eigenphases. This yields a more precise version of the vacuum energy formula, in which a single divergent parameter is exhibited, for a suitable class of fields.The scattering description is introduced by an evaluation of the Green's function, for a sufficiently large time interval, in terms of the discrete modes, and of linear combinations of free particle modes expressed by a unitary matrix which is an extension of that referring to modes of a single frequency. Transition probabilities are derived and summarized in a generating function that serves to evaluate occupation number expectation values for the final state, upon which is based the definition of differential and total scattering cross sections. A discussion is presented of various symmetry operations and the resulting properties of cross sections. Then, a determinantal formula for the individual transition probabilities is used to examine the probability for the persistence of a state, in its dependence upon occupation numbers. An incidental result of this analysis is a qualitative upper limit to total cross sections in relation to the character of the angular distribution. A section is devoted to the properties of eigenphases, including the demonstration of equivalence between phase shifts and eigenphases, and the discussion of alternative procedures for their evaluation in terms of quantities exhibited as convergent power series in the potential. Finally, the determinantal asymptotic behavior is used to obtain a high-energy approximation to the eigenphases for an isotropic scalar potential. The resulting high energy, small angle, form of the scattering cross section is discussed in the extreme quantum and classical limits. An alternative derivation of the high-energy scattering formula is provided in terms of an approximate construction of the Green's function.

Julian Schwinger

1954-06-01T23:59:59.000Z

159

Pauli-Villars regularization of field theories on the light front  

SciTech Connect (OSTI)

Four-dimensional quantum field theories generally require regularization to be well defined. This can be done in various ways, but here we focus on Pauli-Villars (PV) regularization and apply it to nonperturbative calculations of bound states. The philosophy is to introduce enough PV fields to the Lagrangian to regulate the theory perturbatively, including preservation of symmetries, and assume that this is sufficient for the nonperturbative case. The numerical methods usually necessary for nonperturbative bound-state problems are then applied to a finite theory that has the original symmetries. The bound-state problem is formulated as a mass eigenvalue problem in terms of the light-front Hamiltonian. Applications to quantum electrodynamics are discussed.

Hiller, John R. [Department of Physics, University of Minnesota-Duluth, Duluth, Minnesota 55812 (United States)

2010-12-22T23:59:59.000Z

160

Modeling of electroabsorption in semiconductor quantum structures within the eight-band k?p theory  

Science Journals Connector (OSTI)

We have incorporated electric fields into the eight-band k?p theory, which we have applied to heterostructures, in conjunction with the envelope-function approximation. We use the method of Baraff and Gershoni to implement the electric-field effects in a computer program that calculates the optical properties of direct-band-gap heterostructures in one, two, and three dimensions. Using this method, we calculate the interband and intersubband electroabsorption of multiple quantum wells as well as the interband electroabsorption in superlattices. We illustrate the evolution of the Stark localization of the electron wave function under the application of an external electric field in superlattices. Comparison with experimental data, available in the literature, exhibits very good agreement between theory and experiment, with respect to the spectral shape, the absolute magnitude, and the electric-field dependence of the absorption.

Mats-Erik Pistol and David Gershoni

1994-10-15T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


161

6-dimensional Kaluza-Klein Theory for Basic Quantum Particles and Electron-Photon Interaction  

E-Print Network [OSTI]

By extending original Kaluza-Klein theory to 6-dimension, the basic quantum field equations for 0-spin particle, 1-spin particle and 1/2 spin particle with mass >0 are directly derived from 6-dimensional Einstein equations. It shows that the current quantum field equations of basic particles become pure geometry properties under 6-dimension time-space. The field equations of electron and photon can be unified in one 6-dimensional extended Maxwell equation. The equations containing interactions between electron and photon will be derived from Einstein equation under 6-dimension time-space. It shows that the interactions in QED can be considered as the effect of local geometry curvature changing instead of exchange virtual photons.

Xiaodong Chen

2005-01-26T23:59:59.000Z

162

From Quantum Mechanics to String Theory  

E-Print Network [OSTI]

's Constant Newton's constant G appears in the universal law of gravitation: It determines the strength potential energy that we see as mass a spontaneously broken symmetry is a symmetry of the laws of nature. An object of mass m in a gravitational field g feels a force of F = mg This is similar to electromagnetism

163

Quantum Transition State Theory for proton transfer reactions in enzymes  

E-Print Network [OSTI]

We consider the role of quantum effects in the transfer of hyrogen-like species in enzyme-catalysed reactions. This study is stimulated by claims that the observed magnitude and temperature dependence of kinetic isotope effects imply that quantum tunneling below the energy barrier associated with the transition state significantly enhances the reaction rate in many enzymes. We use a path integral approach which provides a general framework to understand tunneling in a quantum system which interacts with an environment at non-zero temperature. Here the quantum system is the active site of the enzyme and the environment is the surrounding protein and water. Tunneling well below the barrier only occurs for temperatures less than a temperature $T_0$ which is determined by the curvature of potential energy surface near the top of the barrier. We argue that for most enzymes this temperature is less than room temperature. For physically reasonable parameters quantum transition state theory gives a quantitative description of the temperature dependence and magnitude of kinetic isotope effects for two classes of enzymes which have been claimed to exhibit signatures of quantum tunneling. The only quantum effects are those associated with the transition state, both reflection at the barrier top and tunneling just below the barrier. We establish that the friction due to the environment is weak and only slightly modifies the reaction rate. Furthermore, at room temperature and for typical energy barriers environmental degrees of freedom with frequencies much less than 1000 cm$^{-1}$ do not have a significant effect on quantum corrections to the reaction rate.

Jacques P. Bothma; Joel Gilmore; Ross H. McKenzie

2009-10-07T23:59:59.000Z

164

Microscopic nonequilibrium theory of quantum well solar cells  

Science Journals Connector (OSTI)

We present a microscopic theory of bipolar quantum well structures in the photovoltaic regime, based on the nonequilibrium Greens function formalism for a multiband tight-binding Hamiltonian. The quantum kinetic equations for the single particle Greens functions of electrons and holes are self-consistently coupled to Poissons equation, including intercarrier scattering on the Hartree level. Relaxation and broadening mechanisms are considered by the inclusion of acoustic and optical electron-phonon interaction in a self-consistent Born approximation of the scattering self-energies. Photogeneration of carriers is described on the same level in terms of a self-energy derived from the standard dipole approximation of the electron-photon interaction. Results from a simple two-band model are shown for the local density of states, spectral response, current spectrum, and current-voltage characteristics for generic single quantum well systems.

U. Aeberhard and R. H. Morf

2008-03-28T23:59:59.000Z

165

Quantum tomography meets dynamical systems and bifurcations theory  

SciTech Connect (OSTI)

A powerful tool for studying geometrical problems in Hilbert spaces is developed. We demonstrate the convergence and robustness of our method in every dimension by considering dynamical systems theory. This method provides numerical solutions to hard problems involving many coupled nonlinear equations in low and high dimensions (e.g., quantum tomography problem, existence and classification of Pauli partners, mutually unbiased bases, complex Hadamard matrices, equiangular tight frames, etc.). Additionally, this tool can be used to find analytical solutions and also to implicitly prove the existence of solutions. Here, we develop the theory for the quantum pure state tomography problem in finite dimensions but this approach is straightforwardly extended to the rest of the problems. We prove that solutions are always attractive fixed points of a nonlinear operator explicitly given. As an application, we show that the statistics collected from three random orthonormal bases is enough to reconstruct pure states from experimental (noisy) data in every dimension d ? 32.

Goyeneche, D., E-mail: dardo.goyeneche@cefop.udec.cl [Departamento de Fisca, Universidad de Concepcin, Casilla 160-C, Concepcin, Chile and Center for Optics and Photonics, Universidad de Concepcin, Casilla 4012, Concepcin (Chile); Torre, A. C. de la [Departamento de Fsica, Universidad Nacional de Mar del Plata, IFIMAR-CONICET, Dean Funes 3350, 7600 Mar del Plata (Argentina)

2014-06-15T23:59:59.000Z

166

The Hamilton-Jacobi Theory, Quantum Mechanics and General Relativity  

E-Print Network [OSTI]

The Hamilton-Jacobi theory of Classical Mechanics can be extended in a novel manner to systems which are fuzzy in the sense that they can be represented by wave functions. A constructive interference of the phases of the wave functions then gives us back Classical systems. In a suitable description this includes both Quantum Theory and General Relativity in the well known superspace formulation. However, there are several nuances which provide insight into these latter systems. All this is considered in this paper together with suitable generalization, to cascades of super universes.

B. G. Sidharth

2005-10-12T23:59:59.000Z

167

Classical Logical versus Quantum Conceptual Thought: Examples in Economics, Decision theory and Concept Theory  

E-Print Network [OSTI]

Inspired by a quantum mechanical formalism to model concepts and their disjunctions and conjunctions, we put forward in this paper a specific hypothesis. Namely that within human thought two superposed layers can be distinguished: (i) a layer given form by an underlying classical deterministic process, incorporating essentially logical thought and its indeterministic version modeled by classical probability theory; (ii) a layer given form under influence of the totality of the surrounding conceptual landscape, where the different concepts figure as individual entities rather than (logical) combinations of others, with measurable quantities such as 'typicality', 'membership', 'representativeness', 'similarity', 'applicability', 'preference' or 'utility' carrying the influences. We call the process in this second layer 'quantum conceptual thought', which is indeterministic in essence, and contains holistic aspects, but is equally well, although very differently, organized than logical thought. A substantial part of the 'quantum conceptual thought process' can be modeled by quantum mechanical probabilistic and mathematical structures. We consider examples of three specific domains of research where the effects of the presence of quantum conceptual thought and its deviations from classical logical thought have been noticed and studied, i.e. economics, decision theory, and concept theories and which provide experimental evidence for our hypothesis.

Diederik Aerts; Bart D'Hooghe

2008-10-29T23:59:59.000Z

168

DOE Science Showcase - Effective field theories | OSTI, US Dept...  

Office of Scientific and Technical Information (OSTI)

some of the latest DOE research endeavors utilizing the EFT concept in his latest white paper 'Effective field theory: In the OSTI Collections'. Large non-Gaussianities in...

169

Purity of states in the theory of open quantum systems  

E-Print Network [OSTI]

The condition of purity of states for a damped harmonic oscillator is considered in the framework of Lindblad theory for open quantum systems. For a special choice of the environment coefficients, the correlated coherent states are shown to be the only states which remain pure all the time during the evolution of the considered system. These states are also the most stable under evolution in the presence of the environment.

A. Isar

2006-04-28T23:59:59.000Z

170

A New Look at the Position Operator in Quantum Theory  

E-Print Network [OSTI]

The postulate that coordinate and momentum representations are related to each other by the Fourier transform has been accepted from the beginning of quantum theory by analogy with classical electrodynamics. As a consequence, an inevitable effect in standard theory is the wave packet spreading (WPS) of the photon coordinate wave function in directions perpendicular to the photon momentum. This leads to the following paradoxes: if the major part of photons emitted by stars are in wave packet states (what is the most probable scenario) then we should see not separate stars but only an almost continuous background from all stars; no anisotropy of the CMB radiation should be observable; data on gamma-ray bursts, signals from directional radio antennas (in particular, in experiments on Shapiro delay) and signals from pulsars show no signs of WPS. In addition, a problem arises why there are no signs of WPS for protons in the LHC ring. We argue that the above postulate is based neither on strong theoretical arguments nor on experimental data and propose a new consistent definition of the position operator. Then WPS in directions perpendicular to the particle momentum is absent and the paradoxes are resolved. Different components of the new position operator do not commute with each other and, as a consequence, there is no wave function in coordinate representation. Implications of the results for entanglement, quantum locality and the problem of time in quantum theory are discussed.

Felix M. Lev

2015-01-07T23:59:59.000Z

171

Quantum dynamics and state-dependent affine gauge fields on CP(N-1)  

E-Print Network [OSTI]

Gauge fields frequently used as an independent construction additional to so-called wave fields of matter. This artificial separation is of course useful in some applications (like Berry's interactions between the "heavy" and "light" sub-systems) but it is restrictive on the fundamental level of "elementary" particles and entangled states. It is shown that the linear superposition of action states and non-linear dynamics of the local dynamical variables form an oscillons of energy representing non-local particles - "lumps" arising together with their "affine gauge potential" agrees with Fubini-Study metric. I use the conservation laws of local dynamical variables (LDV's) during affine parallel transport in complex projective Hilbert space $CP(N-1)$ for twofold aim. Firstly, I formulate the variation problem for the ``affine gauge potential" as system of partial differential equations \\cite{Le1}. Their solutions provide embedding quantum dynamics into dynamical space-time whose state-dependent coordinates related to the qubit spinor subjected to Lorentz transformations of "quantum boosts" and "quantum rotations". Thereby, the problem of quantum measurement being reformulated as the comparison of LDV's during their affine parallel transport in $CP(N-1)$, is inherently connected with space-time emergences. Secondly, the important application of these fields is the completeness of quantum theory. The EPR and Schr\\"odinger's Cat paradoxes are discussed from the point of view of the restored Lorentz invariance due to the affine parallel transport of local Hamiltonian of the soliton-like field.

Peter Leifer

2008-04-11T23:59:59.000Z

172

Griffiths-Hurst-Sherman Inequalities and a Lee-Yang Therorem for the (?4)2 Field Theory  

Science Journals Connector (OSTI)

The Griffiths-Hurst-Sherman inequalities and the Lee-Yang zero theorem in the theory of Ising ferromagnets are shown to hold in a two-dimensional self-coupled Bose quantume field theory with interaction: a?4+b?2-??:. Applications include the continuity of the infinite-volume "magnetization," ??(0)?, away from ?=0. Our results should carry over to three or four dimensions once it is known how to control the ultraviolet divergences in these theories.

Barry Simon and Robert B. Griffiths

1973-05-07T23:59:59.000Z

173

Self-field and magnetic-flux quantum mechanics  

E-Print Network [OSTI]

Self-field and quantized magnetic-flux are employed to generate the quantum numbers n, m, and l of atomic physics. Wave-particle duality is shown to be a natural outcome of having a particle and its self-field.

Paul Harris

2005-04-06T23:59:59.000Z

174

Observable coherence theory for statistically periodic fields Brynmor J. Davis*  

E-Print Network [OSTI]

Observable coherence theory for statistically periodic fields Brynmor J. Davis* The Beckman processes is used to develop classical coherence theory for the measurement of statistically periodicRevA.76.043843 PACS number s : 42.25.Kb, 42.60.Mi, 42.65.Re I. INTRODUCTION Coherence theory 1

Bhargava, Rohit

175

A connection between quantum decision theory and quantum games: The Hamiltonian of Strategic Interaction  

Science Journals Connector (OSTI)

Abstract Experimental economics and studies in psychology show incompatibilities between human behavior and the perfect rationality assumption which do not fit in classical decision theory, but a more general representation in terms of Hilbert spaces can account for them. This paper integrates previous theoretical works in quantum game theory, Yukalov and Sornettes quantum decision theory and Pothos and Busemeyers quantum cognition model by postulating the Hamiltonian of Strategic Interaction which introduces entanglement in the strategic state of the decision-maker. The Hamiltonian is inherited from the algebraic structure of angular momentum in quantum mechanics and the only required parameter, ? ? ? [ 0 , ? ] , represents the strength of the interaction. We consider it as a non-revealed type of the decision-maker. Considering ? ? to be a continuous random variable, phenomena like learning when participating in repeated games and the influence of the amount of disposable information could be considered as an evolution in the mode and shape of the distribution function f ? ? ( t , I ) . This modeling is motivated by the EisertWilkensLewenstein quantization scheme for Prisoners Dilemma game and then it is applied in the Ultimatum game, which is not a simultaneous but a sequential game. Even when this non-revealed type ? ? cannot be directly observed, we can compute observable outcomes: the probabilities of offering different amounts of coins and the probability of the different offers being accepted or not by the other player.

Ismael Martnez-Martnez

2014-01-01T23:59:59.000Z

176

Dynamics of polymers: A mean-field theory  

SciTech Connect (OSTI)

We derive a general mean-field theory of inhomogeneous polymer dynamics; a theory whose form has been speculated and widely applied, but not heretofore derived. Our approach involves a functional integral representation of a Martin-Siggia-Rose (MSR) type description of the exact many-chain dynamics. A saddle point approximation to the generating functional, involving conditions where the MSR action is stationary with respect to a collective density field ? and a conjugate MSR response field ?, produces the desired dynamical mean-field theory. Besides clarifying the proper structure of mean-field theory out of equilibrium, our results have implications for numerical studies of polymer dynamics involving hybrid particle-field simulation techniques such as the single-chain in mean-field method.

Fredrickson, Glenn H. [Department of Chemical Engineering, University of California, Santa Barbara, California 93106 (United States) [Department of Chemical Engineering, University of California, Santa Barbara, California 93106 (United States); Materials Research Laboratory, University of California, Santa Barbara, California 93106 (United States); Department of Materials, University of California, Santa Barbara, California 93106 (United States); Orland, Henri [Institut de Physique Thorique, CE-Saclay, CEA, F-91191 Gif-sur-Yvette Cedex (France)] [Institut de Physique Thorique, CE-Saclay, CEA, F-91191 Gif-sur-Yvette Cedex (France)

2014-02-28T23:59:59.000Z

177

Decision theory and information propagation in quantum physics  

E-Print Network [OSTI]

In recent papers, Zurek has objected to the decision-theoretic approach of Deutsch and Wallace to deriving the Born rule for quantum probabilities on the grounds that it courts circularity. Deutsch and Wallace assume that the many worlds theory is true and that decoherence gives rise to a preferred basis. However, decoherence arguments use the reduced density matrix, which relies upon the partial trace and hence upon the Born Rule for its validity. Using the Heisenberg Picture and quantum Darwinism - the notion that classical information is quantum information that can proliferate in the environment pioneered by Olliver et al - I show that measurement interactions between two systems only create correlations between a specific set of commuting observables of system 1 and a specific set of commuting observables of system 2. This argument picks out a unique basis in which information flows in the correlations between those sets of commuting observables. I then derive the Born rule for both pure and mixed states and answer some other criticisms of the decision theoretic approach to quantum probability.

Alan Forrester

2006-04-18T23:59:59.000Z

178

On the ultraviolet behaviour of quantum fields over noncommutative manifolds  

E-Print Network [OSTI]

By exploiting the relation between Fredholm modules and the Segal-Shale-Stinespring version of canonical quantization, and taking as starting point the first-quantized fields described by Connes' axioms for noncommutative spin geometries, a Hamiltonian framework for fermion quantum fields over noncommutative manifolds is introduced. We analyze the ultraviolet behaviour of second-quantized fields over noncommutative 3-tori, and discuss what behaviour should be expected on other noncommutative spin manifolds.

Varilly, J C; Varilly, Joseph C.; Gracia-Bondia, Jose M.

1999-01-01T23:59:59.000Z

179

Mass Operator and Gauge Field Theory with Five-variable Field Functions  

E-Print Network [OSTI]

To investigate the mass generating problem without Higgs mechanism we present a model in which a new scalar gauge coupling is naturally introduced. Because of the existence of production and annihilation for particles in quantum field theory, we extend the number of independent variables from conventional four space-time dimensions to five ones in order to describe all degrees of freedom for field functions while the conventional space-time is still retained to be the background. The potential fifth variable is nothing but the proper time of particles. In response, a mass operator $(\\hat{m}=-i\\hbar \\frac{\\partial}{\\partial\\tau})$ should be introduced. After that, the lagrangian for free fermion fields in terms of five independent variables and mass operator is written down. By applying the gauge principle, three kinds of vector gauge couplings and one kind of scalar gauge coupling are naturally introduced. In the current scenario, the mass spectrum for all fundamental particles is accounted for in principle by solving the eigenvalue of mass operator under the function of all kinds of interactions. Moreover, there no any auxiliary mechanism including spontaneous symmetry breaking get involved in the model. Therefore, traditional problems in the standard model such as the vacuum energy problem are removed from our model, as well as the hierarchy problem on the mass spectrum for fundamental particles.

ChiYi Chen

2014-04-08T23:59:59.000Z

180

Testing axioms for Quantum Mechanics on Probabilistic toy-theories  

E-Print Network [OSTI]

In Ref. [1] one of the authors proposed postulates for axiomatizing Quantum Mechanics as a "fair operational framework", namely regarding the theory as a set of rules that allow the experimenter to predict future events on the basis of suitable tests, having local control and low experimental complexity. In addition to causality, the following postulates have been considered: PFAITH (existence of a pure preparationally faithful state), and FAITHE (existence of a faithful effect). These postulates have exhibited an unexpected theoretical power, excluding all known nonquantum probabilistic theories. Later in Ref. [2] in addition to causality and PFAITH, postulate LDISCR (local discriminability) and PURIFY (purifiability of all states) have been considered, narrowing the probabilistic theory to something very close to Quantum Mechanics. In the present paper we test the above postulates on some nonquantum probabilistic models. The first model, "the two-box world" is an extension of the Popescu-Rohrlich model, which achieves the greatest violation of the CHSH inequality compatible with the no-signaling principle. The second model "the two-clock world" is actually a full class of models, all having a disk as convex set of states for the local system. One of them corresponds to the "the two-rebit world", namely qubits with real Hilbert space. The third model--"the spin-factor"--is a sort of n-dimensional generalization of the clock. Finally the last model is "the classical probabilistic theory". We see how each model violates some of the proposed postulates, when and how teleportation can be achieved, and we analyze other interesting connections between these postulate violations, along with deep relations between the local and the non-local structures of the probabilistic theory.

Giacomo Mauro D'Ariano; Alessandro Tosini

2009-11-29T23:59:59.000Z

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181

Effective Field Theory of Broken Spatial Diffeomorphisms  

E-Print Network [OSTI]

We study the low energy effective theory describing gravity with broken spatial diffeomorphism invariance. In the unitary gauge, the Goldstone bosons associated with broken diffeomorphisms are eaten and the graviton becomes a massive spin-2 particle with 5 well-behaved degrees of freedom. In this gauge, the most general theory is built with the lowest dimension operators invariant under only temporal diffeomorphisms. Imposing the additional shift and SO(3) internal symmetries, we analyze the perturbations on a FRW background. At linear perturbation level, the observables of this theory are characterized by six parameters, including the usual cosmological parameters and two additional coupling constants for the symmetry-breaking scalars. We discuss several examples relevant to theories of massive gravity.

Lin, Chunshan

2015-01-01T23:59:59.000Z

182

Toward theory of quantum Hall effect in graphene  

E-Print Network [OSTI]

We analyze a gap equation for the propagator of Dirac quasiparticles and conclude that in graphene in a magnetic field, the order parameters connected with the quantum Hall ferromagnetism dynamics and those connected with the magnetic catalysis dynamics necessarily coexist (the latter have the form of Dirac masses and correspond to excitonic condensates). This feature of graphene could lead to important consequences, in particular, for the existence of gapless edge states. Solutions of the gap equation corresponding to recently experimentally discovered novel plateaus in graphene in strong magnetic fields are described.

E. V. Gorbar; V. P. Gusynin; V. A. Miransky

2007-10-18T23:59:59.000Z

183

Book Review: "Quantum Theory as an Emergent Phenomenon", by Stephen L. Adler  

E-Print Network [OSTI]

This is a book review of the book: "Quantum Theory as an Emergent Phenomenon", by Stephen L. Adler (Cambridge University Press - 2004)

A. Bassi

2005-04-28T23:59:59.000Z

184

On the polarization of non-Gaussian optical quantum field: Higher-order optical-polarization  

SciTech Connect (OSTI)

Polarization of light signifies transversal, anisotropic and asymmetrical statistical properties of electromagnetic radiation about the direction of propagation. Traditionally, optical-polarization is characterized by Stokes theory susceptible to be insufficient in assessing the polarization structure of optical quantum fields and, also, does not decipher the twin characteristic polarization parameters (ratio of real amplitudes and difference in phases). An alternative way, in the spirit of classical description of optical-polarization, is introduced which can be generalized to deal higher-order polarization of quantum light, particularly, prepared in non-Gaussian Schrodinger Cat or Cat-like states and entangled bi-modal coherent states. On account of pseudo mono-modal or multi-modal nature of such optical quantum field, higher-order polarization is seen to be highly sensitive to the basis of description. -- Highlights: We have generalized the usual concept of optical-polarization. A concept of higher-order optical-polarization is introduced. This concept is applied to compute the polarization-parameters of non-Gaussian Optical field. To the best of our knowledge, no study is performed which investigates such optical quantum field.

Singh, Ravi S., E-mail: yesora27@gmail.com [Department of Physics, D. D. U. Gorakhpur University, Gorakhpur-273009, (U.P.) (India); Prakash, Hari [Physics Department, University of Allahabad, Allahabad-211002, (U.P.) (India)] [Physics Department, University of Allahabad, Allahabad-211002, (U.P.) (India)

2013-06-15T23:59:59.000Z

185

Probabilistic theories: what is special about Quantum Mechanics?  

E-Print Network [OSTI]

Quantum Mechanics (QM) is a very special probabilistic theory, yet we don't know which operational principles make it so. All axiomatization attempts suffer at least one postulate of a mathematical nature. Here I will analyze the possibility of deriving QM as the mathematical representation of a "fair operational framework", i.e. a set of rules which allows the experimenter to make predictions on future "events" on the basis of suitable "tests", e.g. without interference from uncontrollable sources. Two postulates need to be satisfied by any fair operational framework: NSF: "no-signaling from the future"--for the possibility of making predictions on the basis of past tests; PFAITH: "existence of a preparationally faithful state"--for the possibility of preparing any state and calibrating any test. I will show that all theories satisfying NSF admit a C*-algebra representation of events as linear transformations of effects. Based on a very general notion of dynamical independence, it is easy to see that all such probabilistic theories are "non-signaling without interaction" ("non-signaling" for short)--another requirement for a fair operational framework. Postulate PFAITH then implies the "local observability principle", the tensor-product structure for the linear spaces of states and effects, the impossibility of bit commitment and additional features, such an operational definition of transpose, a scalar product for effects, weak-selfduality of the theory, and more. Dual to Postulate PFAITH an analogous postulate for effects would give additional quantum features, such as teleportation. However, all possible consequences of these postulates still need to be investigated, and it is not clear yet if we can derive QM from the present postulates only. [CONTINUES on manuscript

Giacomo Mauro D'Ariano

2008-07-28T23:59:59.000Z

186

Magnetic Field Control of the Quantum Chaotic Dynamics of Hydrogen Analogues in an Anisotropic Crystal Field  

E-Print Network [OSTI]

We report magnetic field control of the quantum chaotic dynamics of hydrogen analogues in an anisotropic solid state environment. The chaoticity of the system dynamics was quantified by means of energy level statistics. We analyzed the magnetic field dependence of the statistical distribution of the impurity energy levels and found a smooth transition between the Poisson limit and the Wigner limit, i.e. transition between regular Poisson and fully chaotic Wigner dynamics. Effect of the crystal field anisotropy on the quantum chaotic dynamics, which manifests itself in characteristic transitions between regularity and chaos for different field orientations, was demonstrated.

Weihang Zhou; Zhanghai Chen; Bo Zhang; C. H. Yu; Wei Lu; S. C. Shen

2010-03-09T23:59:59.000Z

187

Soft Theorems from Effective Field Theory  

E-Print Network [OSTI]

The singular limits of massless gauge theory amplitudes are described by an effective theory, called soft-collinear effective theory (SCET), which has been applied most successfully to make all-orders predictions for observables in collider physics and weak decays. At tree-level, the emission of a soft gauge boson at subleading order in its energy is given by the Low-Burnett-Kroll theorem, with the angular momentum operator acting on a lower-point amplitude. For well separated particles at tree-level, we prove the Low-Burnett-Kroll theorem using matrix elements of subleading SCET Lagrangian and operator insertions which are individually gauge invariant. These contributions are uniquely determined by gauge invariance and the reparametrization invariance (RPI) symmetry of SCET. RPI in SCET is connected to the infinite-dimensional asymptotic symmetries of the S-matrix. The Low-Burnett-Kroll theorem is generically spoiled by on-shell corrections, including collinear loops and collinear emissions. We demonstrate this explicitly both at tree-level and at one-loop. The effective theory correctly describes these configurations, and we generalize the Low-Burnett-Kroll theorem into a new one-loop subleading soft theorem for amplitudes. Our analysis is presented in a manner that illustrates the wider utility of using effective theory techniques to understand the perturbative S-matrix.

Andrew J. Larkoski; Duff Neill; Iain W. Stewart

2014-12-09T23:59:59.000Z

188

Perturbation Expa]nsion in Dynamical Nuclear Field Theory and Its Relation with Boson Expansion Theory  

Science Journals Connector (OSTI)

......Perturbation Expa]nsion in Dynamical Nuclear Field Theory and Its Relation...April 1990. With the Dynamical Nuclear Field Theory (DNFT) in the...vibrational mode of a spherical nuclear system. Due to the effects...coupling strength and boson energy fails at full self-consistency......

Teruo Kishimoto; Tetsuo Kammuri

1990-09-01T23:59:59.000Z

189

Field-induced decay of quantum vacuum: visualizing pair production in a classical photonic system  

E-Print Network [OSTI]

The phenomenon of vacuum decay, i.e. electron-positron pair production due to the instability of the quantum electrodynamics vacuum in an external field, is a remarkable prediction of Dirac theory whose experimental observation is still lacking. Here a classic wave optics analogue of vacuum decay, based on light propagation in curved waveguide superlattices, is proposed. Our photonic analogue enables a simple and experimentally-accessible visualization in space of the process of pair production as break up of an initially negative-energy Gaussian wave packet, representing an electron in the Dirac sea, under the influence of an oscillating electric field.

Stefano Longhi

2010-09-01T23:59:59.000Z

190

Multichannel Quantum Defect Theory of Strontium Rydberg Series  

E-Print Network [OSTI]

Using the reactance matrix approach, we systematically develop new multichannel quantum defect theory models for the singlet and triplet S, P, D and F states of strontium based on improved energy level measurements. The new models reveal additional insights into the character of doubly excited perturber states, and the improved energy level measurements for certain series allow fine structure to be resolved for those series' perturbers. Comparison between the predictions of the new models and those of previous empirical and \\emph{ab initio} studies reveals good agreement with most series, however some discrepancies are highlighted. Using the multichannel quantum defect theory wave functions derived from our models we calculate other observables such as Land\\'e $g_J$-factors and radiative lifetimes. The analysis reveals the impact of perturbers on the Rydberg state properties of divalent atoms, highlighting the importance of including two-electron effects in the calculations of these properties. The work enables future investigations of properties such as Stark maps and long-range interactions of Rydberg states of strontium.

C L Vaillant; M P A Jones; R M Potvliege

2014-02-24T23:59:59.000Z

191

Consistent Gravitationally-Coupled Spin-2 Field Theory  

E-Print Network [OSTI]

Inspired by the translational gauge structure of teleparallel gravity, the theory for a fundamental massless spin-2 field is constructed. Accordingly, instead of being represented by a symmetric second-rank tensor, the fundamental spin-2 field is assumed to be represented by a spacetime (world) vector field assuming values in the Lie algebra of the translation group. The flat-space theory naturally emerges in the Fierz formalism and is found to be equivalent to the usual metric-based theory. However, the gravitationally coupled theory, with gravitation itself described by teleparallel gravity, is shown not to present the consistency problems of the spin-2 theory constructed on the basis of general relativity.

H. I. Arcos; Tiago Gribl Lucas; J. G. Pereira

2010-05-05T23:59:59.000Z

192

The Theory of Quantized Fields. IV  

Science Journals Connector (OSTI)

The principal development in this paper is the extension of the eigenvalue-eigenvector concept to complete sets of anticommuting operators. With the aid of this formalism we construct a transformation function for the Dirac field, as perturbed by an external source. This transformation function is enlarged to describe phase transformations and, when applied to the isolated Dirac field, yields the charge and energy-momentum eigenvalues and eigenfunctions. The transformation function describing the system in the presence of the source is then used as a generating function to construct the matrices of all ordered products of the field operators, for the isolated Dirac field. The matrices in the occupation number representation are exhibited with a classification that effectively employs a time-reversed description for negative frequency modes. The last section supplements III by constructing the matrices of all ordered products of the potential vector, for the isolated electromagnetic field.

Julian Schwinger

1953-12-01T23:59:59.000Z

193

Field theory: Why have some physicists abandoned it?  

Science Journals Connector (OSTI)

Field theory: Why have some physicists abandoned it? 10.1073/pnas.95.22.12776 Roman Jackiw Massachusetts Institute of Technology, Center for Theoretical Physics, 77 Massachusetts Avenue, 6-320, Cambridge...

Roman Jackiw

1998-01-01T23:59:59.000Z

194

Unified Field Theory and Principle of Representation Invariance  

Science Journals Connector (OSTI)

The main objectives of this article are to postulate a new principle of representation invariance (PRI), and to refine the unified field model of four interactions, derived using the principle of interaction dynamics (PID). Intuitively, PID takes the ... Keywords: Asymptotic freedom, Atom potential, Duality theory of interactions, Electroweak theory, Higgs bosons, Higgs mechanism, Nucleon potential, Principle of Interaction Dynamics (PID), Principle of Representation Invariance (PRI), Quark confinement, Quark potential, Strong interaction force formulas, Unified field equations, Weak interaction force formula, Weak interaction potential

Tian Ma, Shouhong Wang

2014-06-01T23:59:59.000Z

195

Quantum states in rotating electromagnetic fields  

E-Print Network [OSTI]

We describe a new class of exact square integrable solutions of the Pauli and Dirac equation in rotating electromagnetic fields. Solutions obtained by putting equations in the stationary form with help of a coordinate transformation corresponding to the transition into a rotating frame. The transformation is assumed to be Galilean one however a non-Galilean transformation is of particular interest for such solutions. Obtained solutions, especially of Dirac's equation, are valid for arbitrary values of parameters and may be tested experimentally.

B. V. Gisin

2010-11-11T23:59:59.000Z

196

Ising model conformal boundary conditions from open string field theory  

E-Print Network [OSTI]

Given a consistent choice of conformally invariant boundary conditions in a two dimensional conformal field theory, one can construct new consistent boundary conditions by deforming with a relevant boundary operator and flowing to the infrared, or by a marginal deformation. Open string field theory provides a very universal tool to discover and study such new boundary theories. Surprisingly, it also allows one to go in the reverse direction and to uncover solutions with higher boundary entropy. We will illustrate our results on the well studied example of Ising model.

Kudrna, Matej; Schnabl, Martin

2014-01-01T23:59:59.000Z

197

Black Holes as Conformal Field Theories on Horizons  

E-Print Network [OSTI]

We show that any nonextreme black hole can be described by a state with $L_0=E_R$ in a $D=2$ chiral conformal field theory with central charge $c=12E_R$ where $E_R$ is the dimensionless Rindler energy of the black hole. The theory lives in the very near horizon region, i.e. around the origin of Rindler space. Black hole hair is the momentum along the Euclidean dimensionless Rindler time direction. As evidence, we show that $D$--dimensional Schwarzschild black holes and $D=2$ dilatonic ones that are obtained from them by spherical reduction are described by the same conformal field theory states.

Halyo, Edi

2015-01-01T23:59:59.000Z

198

Causation, decision theory, and Bell's theorem: a quantum analogue of the Newcomb problem  

E-Print Network [OSTI]

I apply some of the lessons from quantum theory, in particular from Bell's theorem, to a debate on the foundations of decision theory and causation. By tracing a formal analogy between the basic assumptions of Causal Decision Theory (CDT)--which was developed partly in response to Newcomb's problem-- and those of a Local Hidden Variable (LHV) theory in the context of quantum mechanics, I show that an agent who acts according to CDT and gives any nonzero credence to some possible causal interpretations underlying quantum phenomena should bet against quantum mechanics in some feasible game scenarios involving entangled systems, no matter what evidence they acquire. As a consequence, either the most accepted version of decision theory is wrong, or it provides a practical distinction, in terms of the prescribed behaviour of rational agents, between some metaphysical hypotheses regarding the causal structure underlying quantum mechanics.

Eric G. Cavalcanti

2009-11-12T23:59:59.000Z

199

Effective field theory and integrability in two-dimensional Mott transition  

SciTech Connect (OSTI)

Highlights: > Mott transition in 2d lattice fermion model. > 3D integrability out of 2D. > Effective field theory for Mott transition in 2d. > Double Chern-Simons. > d-Density waves. - Abstract: We study the Mott transition in a two-dimensional lattice spinless fermion model with nearest neighbors density-density interactions. By means of a two-dimensional Jordan-Wigner transformation, the model is mapped onto the lattice XXZ spin model, which is shown to possess a quantum group symmetry as a consequence of a recently found solution of the Zamolodchikov tetrahedron equation. A projection (from three to two space-time dimensions) property of the solution is used to identify the symmetry of the model at the Mott critical point as U{sub q}(sl(2)-circumflex)xU{sub q}(sl(2)-circumflex), with deformation parameter q = -1. Based on this result, the low-energy effective field theory for the model is obtained and shown to be a lattice double Chern-Simons theory with coupling constant k = 1 (with the standard normalization). By further employing the effective filed theory methods, we show that the Mott transition that arises is of topological nature, with vortices in an antiferromagnetic array and matter currents characterized by a d-density wave order parameter. We also analyze the behavior of the system upon weak coupling, and conclude that it undergoes a quantum gas-liquid transition which belongs to the Ising universality class.

Bottesi, Federico L. [Facultad de Ingenieria Pontificia Universidad Catolica Argentina, Av. Alicia Moreau de Justo 1500, 1428 Buenos Aires (Argentina); Physics Department, Comision Nacional de Energia Atomica, Av. Libertador 8250, 1429 Buenos Aires (Argentina); Zemba, Guillermo R., E-mail: zemba@tander.cnea.gov.ar [Facultad de Ingenieria Pontificia Universidad Catolica Argentina, Av. Alicia Moreau de Justo 1500, 1428 Buenos Aires (Argentina); Physics Department, Comision Nacional de Energia Atomica, Av. Libertador 8250, 1429 Buenos Aires (Argentina)

2011-08-15T23:59:59.000Z

200

Slavnov-Taylor Identity for the Effective Field Theory of the Color Glass Condensate  

E-Print Network [OSTI]

We show that a powerful Slavnov-Taylor (ST) identity exists for the Effective Field Theory (EFT) of the Color Glass Condensate (CGC), allowing to control by purely algebraic means the full dependence on the background fields of the fast gluon modes, as well as the correlators of the quantum fluctuations of the classical gluon source. We use this formalism to study the change of the background fast modes (in the Coulomb gauge), induced by the quantum corrections of the semi-fast gluons. We establish the evolution equation for the EFT of the CGC, which points towards an algebraic derivation of the JIMWLK equation. Being based on symmetry-arguments only, the approach can be used to extend the analysis to arbitrary gauges and to higher orders in the perturbation expansion of the EFT.

D. Binosi; A. Quadri; D. N. Triantafyllopoulos

2014-02-18T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


201

Three Dimensional Time Theory: to Unify the Principles of Basic Quantum Physics and Relativity  

E-Print Network [OSTI]

Interpreting quantum mechanics(QM) by classical physics seems like an old topic; And unified theory is in physics frontier; But because the principles of quantum physics and relativity are so different, any theories of trying to unify 4 nature forces should not be considered as completed without truly unifying the basic principles between QM and relativity. This paper will interpret quantum physics by using two extra dimensional time as quantum hidden variables. I'll show that three dimensional time is a bridge to connect basics quantum physics, relativity and string theory. ``Quantum potential'' in Bohm's quantum hidden variable theory is derived from Einstein Lagrangian in 6-dimensional time-space geometry. Statistical effect in the measurement of single particle, non-local properties, de Broglie wave can be naturally derived from the natural properties of three dimensional time. Berry phase, double-slit interference of single particle, uncertainty relation, wave-packet collapse are discussed. The spin and g factor are derived from geometry of extra two time dimensions. Electron can be expressed as time monopole. In the last part of this paper, I'll discuss the relation between three dimensional time and unified theory. Key words: Quantum hidden variable, Interpreting of quantum physics, Berry phase, three dimensional time, unified theory

Xiaodong Chen

2005-10-03T23:59:59.000Z

202

hal00263678, On group theory for quantum gates  

E-Print Network [OSTI]

at the interface of the three pillars: quantum physics, mathematics and computer science. If large-scale quantum of the stabilizer group in terms of maximal normal subgroups [16], sustain the explanation of quantum (de

Paris-Sud XI, Université de

203

The Theory of Quantized Fields. III  

Science Journals Connector (OSTI)

In this paper we discuss the electromagnetic field, as perturbed by a prescribed current. All quantities of physical interest in various situations, eigenvalues, eigenfunctions, and transition probabilities, are derived from a general transformation function which is expressed in a non-Hermitian representation. The problems treated are: the determination of the energy-momentum eigenvalues and eigenfunctions for the isolated electromagnetic field, and the energy eigenvalues and eigenfunctions for the field perturbed by a time-independent current; the evaluation of transition probabilities and photon number expectation values for a time-dependent current that departs from zero only within a finite time interval, and for a time-dependent current that assumes non-vanishing time-independent values initially and finally. The results are applied in a discussion of the infrared catastrophe and of the adiabatic theorem. It is shown how the latter can be exploited to give a uniform formulation for all problems requiring the evaluation of transition probabilities or eigenvalue displacements.

Julian Schwinger

1953-08-01T23:59:59.000Z

204

Holographic thermal field theory on curved spacetimes  

E-Print Network [OSTI]

The AdS/CFT correspondence relates certain strongly coupled CFTs with large effective central charge $c_\\text{eff}$ to semi-classical gravitational theories with AdS asymptotics. We describe recent progress in understanding gravity duals for CFTs on non-trivial spacetimes at finite temperature, both in and out of equilibrium. Such gravity methods provide powerful new tools to access the physics of these strongly coupled theories, which often differs qualitatively from that found at weak coupling. Our discussion begins with basic aspects of AdS/CFT and progresses through thermal CFTs on the Einstein Static Universe and on periodically identified Minkowski spacetime. In the latter context we focus on states describing so-called plasma balls, which become stable at large $c_\\text{eff}$. We then proceed to out-of-equilibrium situations associated with dynamical bulk black holes. In particular, the non-compact nature of these bulk black holes allows stationary solutions with non-Killing horizons that describe time-independent flows of CFT plasma. As final a topic we consider CFTs on black hole spacetimes. This discussion provides insight into how the CFT transports heat between general heat sources and sinks of finite size. In certain phases the coupling to small sources can be strongly suppressed, resulting in negligible heat transport despite the presence of a deconfined plasma with sizeable thermal conductivity. We also present a new result, explaining how this so-called droplet behaviour is related to confinement via a change of conformal frame.

Donald Marolf; Mukund Rangamani; Toby Wiseman

2014-02-22T23:59:59.000Z

205

Conditional probabilities in quantum theory, and the tunneling time controversy  

E-Print Network [OSTI]

It is argued that there is a sensible way to define conditional probabilities in quantum mechanics, assuming only Bayes's theorem and standard quantum theory. These probabilities are equivalent to the ``weak measurement'' predictions due to Aharonov {\\it et al.}, and hence describe the outcomes of real measurements made on subensembles. In particular, this approach is used to address the question of the history of a particle which has tunnelled across a barrier. A {\\it gedankenexperiment} is presented to demonstrate the physically testable implications of the results of these calculations, along with graphs of the time-evolution of the conditional probability distribution for a tunneling particle and for one undergoing allowed transmission. Numerical results are also presented for the effects of loss in a bandgap medium on transmission and on reflection, as a function of the position of the lossy region; such loss should provide a feasible, though indirect, test of the present conclusions. It is argued that the effects of loss on the pulse {\\it delay time} are related to the imaginary value of the momentum of a tunneling particle, and it is suggested that this might help explain a small discrepancy in an earlier experiment.

Aephraim M. Steinberg

1995-02-02T23:59:59.000Z

206

Quark Phase Transition Parameters and $?$-Meson Field in RMF Theory  

E-Print Network [OSTI]

The deconfinement phase transition from hadronic matter to quark matter in the interior of compact stars is investigated. The hadronic phase is described in the framework of relativistic mean-field (RMF) theory, when also the scalar- isovector $\\delta$-meson effective field is taken into account. To describe a quark phase the MIT bag model is used. The changes of the mixed phase threshold parameters caused by the presence of $\\delta$-meson field are investigated.

G. B. Alaverdyan

2009-07-23T23:59:59.000Z

207

Screening effects on field emission from arrays of (5,5) carbon nanotubes: Quantum mechanical simulations  

Science Journals Connector (OSTI)

The simulation of field electron emission from arrays of micrometer-long open-ended (5,5) carbon nanotubes is performed in the framework of quantum theory of many electrons. It is found that the applied external field is strongly screened when the spacing distance is shorter than the length of the carbon nanotubes. The optimal spacing distance is two to three times of the nanotube length, slightly depending on the applied external fields. The electric screening can be described by a factor that is an exponential function of the ratio of the spacing distance to the length of the carbon nanotubes. For a given length, the field enhancement factor decreases sharply as the screening factor is larger than 0.05. The simulation implies that the thickness of the array should be larger than a value, but it does not help the emission much by increasing the thickness a great deal.

Guihua Chen; Weiliang Wang; Jie Peng; Chunshan He; Shaozhi Deng; Ningsheng Xu; Zhibing Li

2007-11-13T23:59:59.000Z

208

Quantum mechanical analogue of the zeroth law of thermodynamics. (On the problem of incorporating Thermodynamics into Quantum Theory)  

E-Print Network [OSTI]

This approach to the incorporation of stochastic thermodynamics into quantum theory is based on the conception of consistent inclusion of the holistic stochastic environmental influence described by wave functions of the arbitrary vacuum, which was proposed in our paper previously. In this study, we implement the possibility of explicitly incorporating the zeroth law of stochastic thermodynamics in the form of the saturated Schr\\"odinger uncertainty relation into quantum theory. This allows comparatively analyzing the sets of states of arbitrary vacuums, namely, squeezed coherent states (SCSs) and correlated coherent states (CCSs). In addition, we compare the results of the construction of stochastic thermodynamics using SCSs and TCCSs with the versions involving the incorporation of thermodynamics into quantum theory developed previously and based on thermofield dynamics and quantum statistical mechanics.

O. N. Golubjeva; A. D. Sukhanov

2013-03-25T23:59:59.000Z

209

Field Test of Measurement-Device-Independent Quantum Key Distribution  

E-Print Network [OSTI]

A main type of obstacles of practical applications of quantum key distribution (QKD) network is various attacks on detection. Measurement-device-independent QKD (MDIQKD) protocol is immune to all these attacks and thus a strong candidate for network security. Recently, several proof-of-principle demonstrations of MDIQKD have been performed. Although novel, those experiments are implemented in the laboratory with secure key rates less than 0.1 bps. Besides, they need manual calibration frequently to maintain the system performance. These aspects render these demonstrations far from practicability. Thus, justification is extremely crucial for practical deployment into the field environment. Here, by developing an automatic feedback MDIQKD system operated at a high clock rate, we perform a field test via deployed fiber network of 30 km total length, achieving a 16.9 bps secure key rate. The result lays the foundation for a global quantum network which can shield from all the detection-side attacks.

Yan-Lin Tang; Hua-Lei Yin; Si-Jing Chen; Yang Liu; Wei-Jun Zhang; Xiao Jiang; Lu Zhang; Jian Wang; Li-Xing You; Jian-Yu Guan; Dong-Xu Yang; Zhen Wang; Hao Liang; Zhen Zhang; Nan Zhou; Xiongfeng Ma; Teng-Yun Chen; Qiang Zhang; Jian-Wei Pan

2014-08-11T23:59:59.000Z

210

Orthogonal-state-based cryptography in quantum mechanics and local post-quantum theories  

E-Print Network [OSTI]

In contrast to the well-known quantum key distribution (QKD) protocols, which encode secret bits in non-orthogonal states, orthogonal-state-based protocols for QKD transmit secret bits deterministically. Even though secure, such a protocol cannot be used to transmit a secret message directly, because an eavesdropper is not prevented from learning something about the direct message before being detected. A quantum secure direct communication (QSDC) scheme satisfies this stronger security requirement. In this work, we study the relationship between security in QKD and QSDC. We show that replacing qubit streaming in a QKD scheme by block-encoding of qubits, we can construct a QSDC scheme. This forms the basis for reducing the security of a QSDC scheme to that of aQKD scheme, in the sense that if the latter is secure, then so is the QSDC scheme built on top of it. We refer to this as \\textit{block reduction}. Further, we show that the security of QKD reduces to that of QSDC, in the sense that if a QSDC protocol is secure, then by sending a random key as the direct message, the corresponding QKD protocol is also secure. This procedure we call as \\textit{key reduction}. Finally, we propose an orthogonal-state-based deterministic key distribution (KD) protocol which is secure in some local post-quantum theories. Its security arises neither from geographic splitting of a code state nor from Heisenberg uncertainty, but from post-measurement disturbance.

S. Arvinda; Anindita Banerjee; Anirban Pathak; R. Srikanth

2014-09-30T23:59:59.000Z

211

An assessment of Evans' unified field theory I  

E-Print Network [OSTI]

Evans developed a classical unified field theory of gravitation and electromagnetism on the background of a spacetime obeying a Riemann-Cartan geometry. This geometry can be characterized by an orthonormal coframe theta and a (metric compatible) Lorentz connection Gamma. These two potentials yield the field strengths torsion T and curvature R. Evans tried to infuse electromagnetic properties into this geometrical framework by putting the coframe theta to be proportional to four extended electromagnetic potentials A; these are assumed to encompass the conventional Maxwellian potential in a suitable limit. The viable Einstein-Cartan(-Sciama-Kibble) theory of gravity was adopted by Evans to describe the gravitational sector of his theory. Including also the results of an accompanying paper by Obukhov and the author, we show that Evans' ansatz for electromagnetism is untenable beyond repair both from a geometrical as well as from a physical point of view. As a consequence, his unified theory is obsolete.

Friedrich W. Hehl

2007-03-10T23:59:59.000Z

212

An assessment of Evans' unified field theory I  

E-Print Network [OSTI]

Evans developed a classical unified field theory of gravitation and electromagnetism on the background of a spacetime obeying a Riemann-Cartan geometry. This geometry can be characterized by an orthonormal coframe theta and a (metric compatible) Lorentz connection Gamma. These two potentials yield the field strengths torsion T and curvature R. Evans tried to infuse electromagnetic properties into this geometrical framework by putting the coframe theta to be proportional to four extended electromagnetic potentials A; these are assumed to encompass the conventional Maxwellian potential in a suitable limit. The viable Einstein-Cartan(-Sciama-Kibble) theory of gravity was adopted by Evans to describe the gravitational sector of his theory. Including also the results of an accompanying paper by Obukhov and the author, we show that Evans' ansatz for electromagnetism is untenable beyond repair both from a geometrical as well as from a physical point of view. As a consequence, his unified theory is obsolete.

Hehl, F W

2007-01-01T23:59:59.000Z

213

Strong-Field Quantum Electrodynamics and Muonic Hydrogen  

E-Print Network [OSTI]

We explore the possibility of a breakdown of perturbative quantum electrodynamics in light muonic bound systems, notably, muonic hydrogen. The average electric field seen by a muon orbiting a proton is shown to be comparable to hydrogenlike Uranium and, notably, larger than the electric field achievable using even the most advanced strong-laser facilities. Following Maltman and Isgur who have shown that fundamental forces such as the meson exchange force may undergo a qualitative change in the strong-coupling regime, we investigate a concomitant possible existence of muon-proton and electron-proton contact interactions, of nonperturbative origin, and their influence on transition frequencies in light one-muon ions.

U. D. Jentschura

2014-11-14T23:59:59.000Z

214

Strong-Field Quantum Electrodynamics and Muonic Hydrogen  

E-Print Network [OSTI]

We explore the possibility of a breakdown of perturbative quantum electrodynamics in light muonic bound systems, notably, muonic hydrogen. The average electric field seen by a muon orbiting a proton is shown to be comparable to hydrogenlike Uranium and, notably, larger than the electric field achievable using even the most advanced strong-laser facilities. Following Maltman and Isgur who have shown that fundamental forces such as the meson exchange force may undergo a qualitative change in the strong-coupling regime, we investigate a concomitant possible existence of muon-proton and electron-proton contact interactions, of nonperturbative origin, and their influence on transition frequencies in light one-muon ions.

Jentschura, U D

2014-01-01T23:59:59.000Z

215

Light-like tachyon condensation in Open String Field Theory  

E-Print Network [OSTI]

We use open string field theory to study the dynamics of unstable branes in the bosonic string theory, in the background of a generic linear dilaton. We find a simple exact solution describing a dynamical interpolation between the perturbative vacuum and the recently discovered nonperturbative tachyon vacuum. In our solution, the open string tachyon increases exponentially along a null direction, after which nonlinearities set in and cause the solution to asymptote to a static state. In particular, the wild oscillations of the open string fields which plague the time-like rolling tachyon solution are entirely absent. Our model thus represents the first example proving that the true tachyon vacuum of open string field theory can be realized as the endpoint of a dynamical transition from the perturbative vacuum.

Simeon Hellerman; Martin Schnabl

2008-03-10T23:59:59.000Z

216

The syntomic regulator for K-theory of fields.  

E-Print Network [OSTI]

We define complexes analogous to Goncharov's complexes for the K-theory of discrete valuation rings of characteristic zero. Under suitable assumptions in K-theory, there is a map from the cohomology of those complexes to the K-theory of the ring. In case the ring is the localization of the ring of integers in a number field, there are no assumptions necessary. We compute the composition of our map to the K-theory with the syntomic regulator. The result can be described in terms of a p-adic polylogarithm. Finally, we apply our theory in order to compute the regulator to syntomic cohomology on Beilinson's cyclotomic elements. The result is again given by the p-adic polylogarithm. This last result is related to one by Somekawa and generalizes work by Gros.

Amnon Besser; Rob de Jeu

217

Quantum Energy Teleportation with Electromagnetic Field: Discrete vs. Continuous Variables  

E-Print Network [OSTI]

Local measurements of quantum fluctuation in the vacuum state of electromagnetic field require energy infusion to the field. The infused energy is diffused to spatial infinity with light velocity and the state of the field soon becomes a local vacuum with zero energy around the measurement area. Of cource we cannot retrieve energy from this measurement area if we do not know the measurement result of the fluctuation. However, if the measurement result is available for us, we are able to extract energy from the local vacuum of the field, applying the protocol of quantum energy teleportation recently proposed. By performing a local unitary operation around the measurement area dependent on the measurement result, the fluctuaion of zero-point oscillation is squeezed and negative energy density appears around the area, accompanied by extraction of positive energy from the field. In this paper, we compare two different protocols of the energy retrieval. In the first protocol, a 1/2 spin is coupled with the fluctua...

Hotta, Masahiro

2009-01-01T23:59:59.000Z

218

Advances in Quantum Chemistry, 43, 95-117 (2003) Differentiability in density-functional theory  

E-Print Network [OSTI]

Advances in Quantum Chemistry, 43, 95-117 (2003) Differentiability in density-functional theory in density-functional theory (DFT) is investigated, and it is shown that the so-called Levy- Lieb functional The differentiability of density functionals is of fundamental importance in Density-Functional Theory (DFT) and forms

Lindgren, Ingvar

219

Electric-field-induced spin depolarization in graphene quantum dots  

Science Journals Connector (OSTI)

We study the effect of the in-plane electric field on the magnetic properties of charge-neutral triangular zigzag graphene quantum dot (GQD) by using the mean-field Hubbard Hamiltonian. Our calculated results show that spin depolarization begins to occur when the electric field is beyond some critical value. The spin-density distribution is more concentrated in the region of the GQDs with smaller electrostatic potential. This phenomenon is attributed to the competition between the many-body electron-electron interaction and the external electrostatic potential. Numerical results also show that the total spin of larger GQDs are easier to depolarize than the total spin of smaller GQDs. Moreover, the spin of GQDs with weak edge disorder still respond to an electric field but in a more irregular way. Our findings provide a path to electrically tuning the magnetic properties of GQDs.

Wen-Long Ma and Shu-Shen Li

2012-07-30T23:59:59.000Z

220

Absence of cosmological constant problem in special relativistic field theory of gravity  

E-Print Network [OSTI]

The principles of quantum field theory in flat spacetime suggest that gravity is mediated by a massless particle with helicity $\\pm2$, the so-called graviton. It is regarded as textbook knowledge that, when the self-coupling of a particle with these properties is considered, the long-wavelength structure of such a nonlinear theory is fixed to be that of general relativity. However, here we show that these arguments conceal an implicit assumption which is surreptitiously motivated by the very knowledge of general relativity. This is shown by providing a counterexample: we revisit a nonlinear theory of gravity which is not structurally equivalent to general relativity and that, in the non-interacting limit, describes a free helicity $\\pm2$ graviton. We explicitly prove that this theory can be understood as the result of self-coupling in complete parallelism to the well-known case of general relativity. The assumption which was seen as natural in previous analyses but biased the result is pointed out. This special relativistic field theory of gravity implies the decoupling of vacuum zero-point energies of matter and passes all the known experimental tests in gravitation.

Carlos Barcel; Ral Carballo-Rubio; Luis J. Garay

2014-06-30T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
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221

The Measurement Process in Local Quantum Theory and the EPR Paradox  

E-Print Network [OSTI]

We describe in a qualitative way a possible picture of the Measurement Process in Quantum Mechanics, which takes into account: 1. the finite and non zero time duration T of the interaction between the observed system and the microscopic part of the measurement apparatus; 2. the finite space size R of that apparatus; 3. the fact that the macroscopic part of the measurement apparatus, having the role of amplifying the effect of that interaction to a macroscopic scale, is composed by a very large but finite number N of particles. The conventional picture of the measurement, as an instantaneous action turning a pure state into a mixture, arises only in the limit in which N and R tend to infinity, and T tends to 0. We sketch here a proposed scheme, which still ought to be made mathematically precise in order to analyse its implications and to test it in specific models, where we argue that in Quantum Field Theory this picture should apply to the unique time evolution expressing the dynamics of a given theory, and should comply with the Principle of Locality. We comment on the Einstein Podolski Rosen thought experiment (partly modifying the discussion on this point in an earlier version of this note), reformulated here only in terms of local observables (rather than global ones, as one particle or polarisation observables). The local picture of the measurement process helps to make it clear that there is no conflict with the Principle of Locality.

Sergio Doplicher

2009-08-04T23:59:59.000Z

222

Aspects of finite temperature field theories in Ads/CFT  

E-Print Network [OSTI]

In this dissertation I study some properties of field theories at finite temperature using the AdS/CFT correspondence. I present a general proof of an "inheritance principle" satisfied by a weakly coupled SU(N) (or U(N)) ...

Brigante, Mauro

2008-01-01T23:59:59.000Z

223

Comments on the Casimir energy in supersymmetric field theories  

E-Print Network [OSTI]

We study the Casimir energy of four-dimensional supersymmetric gauge theories in the context of the rigid limit of new minimal supergravity. Firstly, revisiting the computation of the localized partition function on $S^1\\times S^3$, we recover the supersymmetric Casimir energy. Secondly, we consider the same theories in the Hamiltonian formalism on $\\mathbb{R}\\times S^3$, focussing on the free limit and including a one-parameter family of background gauge fields along $\\mathbb{R}$. We compute the vacuum expectation value of the canonical Hamiltonian using zeta function regularization, and show that this interpolates between the supersymmetric Casimir energy and the ordinary Casimir energy of a supersymmetric free field theory.

Jakob Lorenzen; Dario Martelli

2014-12-23T23:59:59.000Z

224

A Continuous Field Theory of Matter and Electromagnetism  

E-Print Network [OSTI]

A continuous field theory of matter and electromagnetism is developed. The starting point of the theory is the classical Maxwell equations which are directly tied to the Riemann-Christoffel curvature tensor. This is done through the derivatives of the Maxwell tensor which are equated to a vector field contracted with the curvature tensor. The electromagnetic portion of the theory is shown to be equivalent to the classical Maxwell equations with the addition of a hidden variable. Because the proposed equations describing electromagnetism and matter differ from the classical Maxwell-Einstein equations, their ability to describe classical physics is shown for several situations by direct calculation. The inclusion of antimatter and the possibility of particle-like solutions exhibiting both quantized charge and mass are discussed.

Raymond J. Beach

2012-08-31T23:59:59.000Z

225

On the Compatibility Between Quantum and Relativistic Effects in an Electromagnetic Bridge Theory  

E-Print Network [OSTI]

The Dipolar Electromagnetic Source (DEMS) model, based on the Poynting Vector Conjecture, conduces in Bridge Theory to a derivation of the Lorentz transformation connecting pairs of events. The results prove a full compatibility between quantum and relativistic effects.

Massimo Auci

2010-03-18T23:59:59.000Z

226

Incompatibility between Self-Observing Consciousness and the Axioms of Quantum theory  

E-Print Network [OSTI]

Based on the standard axioms of quantum theory, we provide a counter-example which invalidates the full compatibility between consciousness and quantum theory. In particular, we present an example of a natural phenomenon in which an observer's the mental state can be fully described in mathematical terms analogous to the state vector that is being observed. This mathematical description of the observer's mental state enables us to examine consciousness within the standard axioms of quantum theory. The separation between the observing party and the physical system being observed, imposed by the axiom of quantum theory, poses a problem when the observer is observing his own mental state, i.e., self-observing consciousness.

Song, Daegene

2007-01-01T23:59:59.000Z

227

Incompatibility between Self-Observing Consciousness and the Axioms of Quantum theory  

E-Print Network [OSTI]

Based on the standard axioms of quantum theory, we provide a counter-example which invalidates the full compatibility between consciousness and quantum theory. In particular, we present an example of a natural phenomenon in which an observer's the mental state can be fully described in mathematical terms analogous to the state vector that is being observed. This mathematical description of the observer's mental state enables us to examine consciousness within the standard axioms of quantum theory. The separation between the observing party and the physical system being observed, imposed by the axiom of quantum theory, poses a problem when the observer is observing his own mental state, i.e., self-observing consciousness.

Daegene Song

2007-06-28T23:59:59.000Z

228

Statistical Separability and the Consistency between Quantum Theory, Relativity and the Causality  

E-Print Network [OSTI]

We show that the non-locality together with the statistical character makes the world statistically separable. The super-luminal signal transmission is impossible. The quantum theory is therefore consistent with the relativity and the causality.

Qi-Ren Zhang

2005-12-19T23:59:59.000Z

229

Generalized Galilean Transformations and the Measurement Problem in the Entropic Dynamics Approach to Quantum Theory  

E-Print Network [OSTI]

Quantum mechanics is an extremely successful and accurate physical theory, yet since its inception, it has been afflicted with numerous conceptual difficulties. The primary subject of this thesis is the theory of entropic quantum dynamics (EQD), which seeks to avoid these conceptual problems by interpreting quantum theory from an informational perspective. We begin by reviewing probability theory as a means of rationally quantifying uncertainties. We then discuss how probabilities can be updated with the method of maximum entropy (ME). We then review some motivating difficulties in quantum mechanics before discussing Caticha's work in deriving quantum theory from the approach of entropic dynamics. After entropic dynamics is introduced, we develop the concepts of symmetries and transformations from an informational perspective. The primary result is the formulation of a symmetry condition that any transformation must satisfy in order to qualify as a symmetry in EQD. We then proceed to apply this condition to the extended Galilean transformation. This transformation is of interest as it exhibits features of both special and general relativity. The transformation yields a gravitational potential that arises from an equivalence of information. We conclude the thesis with a discussion of the measurement problem in quantum mechanics. We discuss the difficulties that arise in the standard quantum mechanical approach to measurement before developing our theory of entropic measurement. In entropic dynamics, position is the only observable. We show how a theory built on this one observable can account for the multitude of measurements present in quantum theory. Furthermore, we show that the Born rule need not be postulated, but can be derived in EQD. Finally, we show how the wave function can be updated by the ME method as the phase is constructed purely in terms of probabilities.

David T. Johnson

2011-05-06T23:59:59.000Z

230

Cascading and local-field effects in non-linear optics revisited: A quantum-field picture based on exchange of photons  

SciTech Connect (OSTI)

The semi-classical theory of radiation-matter coupling misses local-field effects that may alter the pulse time-ordering and cascading that leads to the generation of new signals. These are then introduced macroscopically by solving Maxwell's equations. This procedure is convenient and intuitive but ad hoc. We show that both effects emerge naturally by including coupling to quantum modes of the radiation field that are initially in the vacuum state to second order. This approach is systematic and suggests a more general class of corrections that only arise in a QED framework. In the semi-classical theory, which only includes classical field modes, the susceptibility of a collection of N non-interacting molecules is additive and scales as N. Second-order coupling to a vacuum mode generates an effective retarded interaction that leads to cascading and local field effects both of which scale as N{sup 2}.

Bennett, Kochise, E-mail: kcbennet@uci.edu; Mukamel, Shaul, E-mail: smukamel@uci.edu [Chemistry Department, University of California, Irvine, California 92697-2025 (United States)] [Chemistry Department, University of California, Irvine, California 92697-2025 (United States)

2014-01-28T23:59:59.000Z

231

Effective field theory for dilute fermions with pairing  

SciTech Connect (OSTI)

Effective field theory (EFT) methods for a uniform system of fermions with short-range, natural interactions are extended to include pairing correlations, as part of a program to develop a systematic Kohn-Sham density functional theory (DFT) for medium and heavy nuclei. An effective action formalism for local composite operators leads to a free-energy functional that includes pairing by applying an inversion method order by order in the EFT expansion. A consistent renormalization scheme is demonstrated for the uniform system through next-to-leading order, which includes induced-interaction corrections to pairing.

Furnstahl, R.J. [Department of Physics, Ohio State University, Columbus, OH 43210 (United States)], E-mail: furnstahl.1@osu.edu; Hammer, H.-W. [Helmholtz-Institut fuer Strahlen- und Kernphysik (Theorie), Universitaet Bonn, Nussallee 14-16, D-53115 Bonn (Germany)], E-mail: hammer@itkp.uni-bonn.de; Puglia, S.J. [SBIG PLC, Berkeley Square House, London W1J 6BR (United Kingdom)], E-mail: spuglia@sbiguk.com

2007-11-15T23:59:59.000Z

232

Dirac-Brueckner-Hartree-Fock versus chiral effective field theory  

E-Print Network [OSTI]

We compare nuclear and neutron matter predictions based on two different ab initio approaches to nuclear forces and the nuclear many-body problem. The first consists of a realistic meson-theoretic nucleon-nucleon potential together with the relativistic counterpart of the Brueckner-Hartree-Fock theory of nuclear matter. The second is based on chiral effective field theory, with density-dependent interactions derived from leading order chiral three-nucleon forces. We find the results to be very close and conclude that both approaches contain important features governing the physics of nuclear and neutron matter.

F. Sammarruca; B. Chen; L. Coraggio; N. Itaco; R. Machleidt

2012-09-22T23:59:59.000Z

233

Dirac-Brueckner-Hartree-Fock versus chiral effective field theory  

E-Print Network [OSTI]

We compare nuclear and neutron matter predictions based on two different ab initio approaches to nuclear forces and the nuclear many-body problem. The first consists of a realistic meson-theoretic nucleon-nucleon potential together with the relativistic counterpart of the Brueckner-Hartree-Fock theory of nuclear matter. The second is based on chiral effective field theory, with density-dependent interactions derived from leading order chiral three-nucleon forces. We find the results to be very close and conclude that both approaches contain important features governing the physics of nuclear and neutron matter.

Sammarruca, F; Coraggio, L; Itaco, N; Machleidt, R

2012-01-01T23:59:59.000Z

234

Proton-proton fusion in lattice effective field theory  

E-Print Network [OSTI]

The proton-proton fusion rate is calculated at low energy in a lattice effective field theory (EFT) formulation. The strong and the Coulomb interactions are treated non-perturbatively at leading order in the EFT. The lattice results are shown to accurately describe the low energy cross section within the validity of the theory at energies relevant to solar physics. In prior work in the literature, Coulomb effects were generally not included in non-perturbative lattice calculations. Work presented here is of general interest in nuclear lattice EFT calculations that involve Coulomb effects at low energy. It complements recent developments of the adiabatic projection method for lattice calculations of nuclear reactions.

Gautam Rupak; Pranaam Ravi

2014-11-10T23:59:59.000Z

235

Stochastic quantization of real-time thermal field theory  

SciTech Connect (OSTI)

We use the stochastic quantization method to obtain the free scalar propagator of a finite temperature field theory formulated in the Minkowski space-time. First, we use the Markovian stochastic quantization approach to present the two-point function of the theory. Second, we assume a Langevin equation with a memory kernel and a colored noise. The convergence of the Markovian and non-Markovian stochastic processes in the asymptotic limit of the fictitious time is obtained. Our formalism can be the starting point to discuss systems at finite temperature out of equilibrium.

Aguiar, T. C. de; Svaiter, N. F. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rua Dr. Xavier Sigaud 150, Rio de Janeiro 22290-180, Rio de Janeiro (Brazil); Menezes, G. [Instituto de Fisica Teorica, Universidade Estadual Paulista, Rua Dr. Bento Teobaldo Ferraz 271, Bloco II, Barra Funda, Sao Paulo 01140-070, Sao Paulo (Brazil)

2010-10-15T23:59:59.000Z

236

IASSNS-HEP-90/58 Mean-field theory of spin-liquid states  

E-Print Network [OSTI]

and topological orders* X. G. Wen Institute for Advanced Study Princeton, NJ 08540 ABSTRACT: The mean field theory are based on the mean field theory, the concept of the topological order and the associated universal theory. We also discuss the dynamical stability of the mean field theory. * Research supported by DOE

Wen, Xiao-Gang

237

QLib - A Matlab Package for Quantum Information Theory Calculations with Applications  

E-Print Network [OSTI]

Developing intuition about quantum information theory problems is difficult, as is verifying or ruling-out of hypothesis. We present a Matlab package intended to provide the QIT community with a new and powerful tool-set for quantum information theory calculations. The package covers most of the "QI textbook" and includes novel parametrization of quantum objects and a robust optimization mechanism. New ways of re-examining well-known results is demonstrated. QLib is designed to be further developed and enhanced by the community and is available for download at www.qlib.info

Shai Machnes

2007-08-03T23:59:59.000Z

238

Quantum field theoretical description for the reflectivity of graphene  

E-Print Network [OSTI]

We derive the polarization tensor of graphene at nonzero temperature in (2+1)-dimensional space-time. The obtained tensor coincides with the previously known one at all Matsubara frequencies, but, in contrast to it, admits analytic continuation to the real frequency axis satisfying all physical requirements. Using the obtained representation for the polarization tensor, we develope quantum field theoretical description for the reflectivity of graphene. The analytic asymptotic expressions for the reflection coefficients and reflectivities at low and high frequencies are derived for both independent polarizations of the electromagnetic field. The dependencies of reflectivities on the frequency and angle of incidence are investigated. Numerical computations using the exact expressions for the polarization tensor are performed and application regions for the analytic asymptotic results are determined.

Bordag, M; Mostepanenko, V M; Petrov, V M

2015-01-01T23:59:59.000Z

239

Theory of coherent dynamic nuclear polarization in quantum dots  

Science Journals Connector (OSTI)

We consider the production of dynamic nuclear spin polarization (DNP) in a two-electron double quantum dot, in which the electronic levels are repeatedly swept through a singlet-triplet avoided crossing. Our analysis helps to elucidate the intriguing interplay between electron-nuclear hyperfine coupling, electronic spin-orbit coupling, and electron and nuclear Larmor precession in an externally applied magnetic field in guiding the production of DNP. In particular, we specifically address the roles of multiple nuclear spin species. By treating the nuclear spin dynamics semiclassically, we identify two contributions to the DNP production rate, a geometric contribution and a dynamic contribution, which depend in very different ways on control parameters such as the sweep rate and holding time near the level crossing. We find that the dynamical contribution dominates the DNP when the system is held near the singlet-triplet avoided crossing for a time on the order of the nuclear Larmor period. Detailed numerical calculations provide a physical picture for understanding the oscillations observed by Foletti et al. in arXiv:0801.3613.

Izhar Neder; Mark S. Rudner; Bertrand I. Halperin

2014-02-04T23:59:59.000Z

240

SciTech Connect: Heavy Quarks, QCD, and Effective Field Theory  

Office of Scientific and Technical Information (OSTI)

Quarks, Quarkonium, Soft-Collinear Effective Theory, Effective Field Theories Word Cloud More Like This Full Text preview image File size NAView Full Text View Full Text DOI:...

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


241

SciTech Connect: An effective field theory for collinear and...  

Office of Scientific and Technical Information (OSTI)

Heavy to light decays An effective field theory for collinear and soft gluons: Heavy to light decays We construct the Lagrangian for an effective theory of highly energetic...

242

Questions and Answers - How can I explain the Quantum/Wave theory to my  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

What is a meniscus? What is a meniscus? Previous Question (What is a meniscus?) Questions and Answers Main Index Next Question (What is the sun made from?) What is the sun made from? How can I explain the Quantum/Wave theory to my class? You can't! The folks who have postulated the quantum nature of matter and wave-particle duality, and other quantum theories have trouble explaining it in terms other than mathematical equations. When trying to explain it in conceptual terms, we're asked to accept things that don't make sense, and in some ways, physicists use this as justification that the theory is correct. Anyway, here are a couple ideas for discussing the quantum/wave properties of energy. Until around 1900, when Max Planck developed the idea of quanta, energy had been thought to be a phenomenon of continuous flow - basically waves.

243

Scalar $?^4$ field theory for active-particle phase separation  

E-Print Network [OSTI]

Recent theories predict phase separation among orientationally disordered active particles whose propulsion speed decreases rapidly enough with density. Coarse-grained models of this process show time-reversal symmetry (detailed balance) to be restored for uniform states, but broken by gradient terms; hence detailed-balance violation is strongly coupled to interfacial phenomena. To explore the subtle generic physics resulting from such coupling we here introduce `Active Model B'. This is a scalar $\\phi^4$ field theory (or phase-field model) that minimally violates detailed balance via a leading-order square-gradient term. We find that this additional term has modest effects on coarsening dynamics, but alters the static phase diagram by creating a jump in (thermodynamic) pressure across flat interfaces. Both results are surprising, since interfacial phenomena are always strongly implicated in coarsening dynamics but are, in detailed-balance systems, irrelevant for phase equilibria.

Raphael Wittkowski; Adriano Tiribocchi; Joakim Stenhammar; Rosalind J. Allen; Davide Marenduzzo; Michael E. Cates

2014-07-11T23:59:59.000Z

244

The perturbative structure of spin glass field theory  

E-Print Network [OSTI]

Cubic replicated field theory is used to study the glassy phase of the short-range Ising spin glass just below the transition temperature, and for systems above, at, and slightly below the upper critical dimension six. The order parameter function is computed up to two-loop order. There are two, well-separated bands in the mass spectrum, just as in mean field theory. The small mass band acts as an infrared cutoff, whereas contributions from the large mass region can be computed perturbatively (d>6), or interpreted by the epsilon-expansion around the critical fixed point (d=6-epsilon). The one-loop calculation of the (momentum-dependent) longitudinal mass, and the whole replicon sector is also presented. The innocuous behavior of the replicon masses while crossing the upper critical dimension shows that the ultrametric replica symmetry broken phase remains stable below six dimensions.

Tams Temesvri

2013-12-27T23:59:59.000Z

245

Tachyon solutions in boundary and open string field theory  

SciTech Connect (OSTI)

We construct rolling tachyon solutions of open and boundary string field theory (OSFT and BSFT, respectively), in the bosonic and supersymmetric (susy) case. The wildly oscillating solution of susy OSFT is recovered, together with a family of time-dependent BSFT solutions, for the bosonic and susy string. These are parametrized by an arbitrary constant r involved in solving the Green equation of the target fields. When r=0 we recover previous results in BSFT, whereas for r attaining the value predicted by OSFT it is shown that the bosonic OSFT solution is the derivative of the boundary one; in the supersymmetric case the relation between the two solutions is more complicated. This technical correspondence sheds some light on the nature of wild oscillations, which appear in both theories whenever r>0.

Calcagni, Gianluca; Nardelli, Giuseppe [Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH (United Kingdom) and Institute for Gravitation and the Cosmos, Department of Physics, Pennsylvania State University, 104 Davey Lab, University Park, Pennsylvania 16802 (United States); Dipartimento di Matematica e Fisica, Universita Cattolica, via Musei 41, 25121 Brescia (Italy) and INFN Gruppo Collegato di Trento, Universita di Trento, 38050 Povo, Trento (Italy)

2008-12-15T23:59:59.000Z

246

Tachyon solutions in boundary and cubic string field theory  

E-Print Network [OSTI]

We construct rolling tachyon solutions of open and boundary string field theory (OSFT and BSFT, respectively), in the bosonic and supersymmetric (susy) case. The wildly oscillating solution of susy OSFT is recovered, together with a family of time-dependent BSFT solutions for the bosonic and susy string. These are parametrized by an arbitrary constant r involved in solving the Green equation of the target fields. When r=0 we recover previous results in BSFT, whereas for r attaining the value predicted by OSFT it is shown that the bosonic OSFT solution is the derivative of the boundary one; in the supersymmetric case the relation between the two solutions is more complicated. This technical correspondence sheds some light on the nature of wild oscillations, which appear in both theories whenever r>0.

Gianluca Calcagni; Giuseppe Nardelli

2007-08-02T23:59:59.000Z

247

Radiative Neutron Capture on Carbon-14 in Effective Field Theory  

E-Print Network [OSTI]

The cross section for radiative capture of neutron on carbon-14 is calculated using the model-independent formalism of halo effective field theory. The dominant contribution from E1 transition is considered, and the cross section is expressed in terms of elastic scattering parameters of the effective range expansion. Contributions from both resonant and non-resonant interaction are calculated. Significant interference between these leads to a capture contribution that deviates from simple Breit-Wigner resonance form.

Gautam Rupak; Lakma Fernando; Akshay Vaghani

2012-04-19T23:59:59.000Z

248

Radiative Neutron Capture on Carbon-14 in Effective Field Theory  

E-Print Network [OSTI]

The cross section for radiative capture of neutron on carbon-14 is calculated using the model-independent formalism of halo effective field theory. The dominant contribution from E1 transition is considered, and the cross section is expressed in terms of elastic scattering parameters of the effective range expansion. Contributions from both resonant and non-resonant interaction are calculated. Significant interference between these leads to a capture contribution that deviates from simple Breit-Wigner resonance form.

Rupak, Gautam; Vaghani, Akshay

2012-01-01T23:59:59.000Z

249

Theory of Coulomb-blockade oscillations in the conductance of a quantum dot  

Science Journals Connector (OSTI)

A linear-response theory is developed for resonant tunneling through a quantum dot of small capacitance, in the regime of thermally broadened resonances. The theory extends the classical theory of Coulomb-blockade oscillations by Kulik and Shekhter to the resonant-tunneling regime. Both the cases of negligible and strong inelastic scattering in the quantum dot are considered. Effects from the non-Fermi-Dirac distribution of electrons among the energy levels (occurring when kT is comparable to the level separation) are fully included. Explicit analytic results are obtained for the periodicity, amplitude, line shape, and activation energy of the conductance oscillations.

C. W. J. Beenakker

1991-07-15T23:59:59.000Z

250

Low-energy effective theory of Fermi surface coupled with U(1) gauge field in 2+1 dimensions  

SciTech Connect (OSTI)

We study the low-energy effective theory for a non-Fermi-liquid state in 2+1 dimensions, where a transverse U(1) gauge field is coupled with a patch of Fermi surface with N flavors of fermion in the large N limit. In the low-energy limit, quantum corrections are classified according to the genus of the two-dimensional surface on which Feynman diagrams can be drawn without a crossing in a double line representation and all planar diagrams are important in the leading order. The emerging theory has the similar structure to the four-dimensional SU(N) gauge theory in the large N limit. Because of strong quantum fluctuations caused by the abundant low-energy excitations near the Fermi surface, low-energy fermions remain strongly coupled even in the large N limit. As a result, there are infinitely many quantum corrections that contribute to the leading frequency dependence of the Green's function of fermion on the Fermi surface. On the contrary, the boson self-energy is not modified beyond the one-loop level and the theory is stable in the large N limit. The nonperturbative nature of the theory also shows up in correlation functions of gauge-invariant operators.

Lee, Sung-Sik [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1 (Canada)

2009-10-15T23:59:59.000Z

251

Quantum Mechanics, Group Theory, and C60 Frank Rioux  

E-Print Network [OSTI]

production in macroscopic amounts2 has generated a tremendous amount of research activity in chemistry and the angular momentum quantum number. (1) Just as the quantum mechanical solution for the one-electron hydrogen all other levels are completely filled. Using traditional group theoretical methods6 , it can be shown that

Rioux, Frank

252

Multiscale quantum-defect theory and its application to atomic spectrum  

E-Print Network [OSTI]

We present a multiscale quantum-defect theory based on the first analytic solution for a two-scale long range potential consisting of a Coulomb potential and a polarization potential. In its application to atomic structure, the theory extends the systematic understanding of atomic Rydberg states, as afforded by the standard single-scale quantum-defect theory, to a much greater range of energies to include the first few excited states and even the ground state. Such a level of understanding has important implications not only on atomic structure, but also on the electronic structure of molecules and on atomic and molecular interactions and reactions. We demonstrate the theory by showing that it provides an analytic description of the energy variations of the standard Coulomb quantum defects for alkali-metal atoms.

Fu, Haixiang; Tey, Meng Khoon; You, Li; Gao, Bo

2015-01-01T23:59:59.000Z

253

Quantum theory of nonequilibrium processes II. Application to nuclear collisions  

SciTech Connect (OSTI)

In the high-energy (E/sub lab/> or =200 MeV/nucl) heavy ion-collisions, the quantum uncertainty of nucleon energies, given by the collision frequency, is of the order of (50-100) MeV. At hundreds MeV/nucl beam energies, the uncertainty is comparable with nucleon energies in the equal ion-velocity frame, indicating a quantum character of the dynamics. The quantum dynamics of a collision process is examined using nonequilibrium Green's function methods. Numerical calculations of collisions in an interpenetrating nuclear matter model, at the energy E/sub lab/ = 400 MeV/nucl, are performed. Comparison of the quantum dynamics, with the classical Markovian dynamics from the Boltzmann equation, reveals effects of the ill-defined nucleon energies in the nucleon momentum distribution. It is shown that the quantum dynamics proceeds twice as slow as Boltzmann dynamics, but the off-shell kinematics compensates for this somewhat.

Danielewicz, P.

1984-02-01T23:59:59.000Z

254

Absence of cosmological constant problem in special relativistic field theory of gravity  

E-Print Network [OSTI]

The principles of quantum field theory in flat spacetime suggest that gravity is mediated by a massless particle with helicity $\\pm2$, the so-called graviton. It is regarded as textbook knowledge that, when the self-coupling of a particle with these properties is considered, the long-wavelength structure of such a nonlinear theory is fixed to be that of general relativity. However, here we show that these arguments conceal an implicit assumption which is surreptitiously motivated by the very knowledge of general relativity. This is shown by providing a counterexample: we revisit a nonlinear theory of gravity which is not structurally equivalent to general relativity and that, in the non-interacting limit, describes a free helicity $\\pm2$ graviton. We explicitly prove that this theory can be understood as the result of self-coupling in complete parallelism to the well-known case of general relativity. The assumption which was seen as natural in previous analyses but biased the result is pointed out. This speci...

Barcel, Carlos; Garay, Luis J

2014-01-01T23:59:59.000Z

255

Bohr - Planck quantum theory, (Tesla) magnetic monopoles and fine structure constant  

E-Print Network [OSTI]

In this work we apply Bohr-Planck (Old quantum atomic and radiation) theory, i.e. and quasi-classical methods for analysis of the magnetic monopoles and other problems. We reproduce exactly some basic elements of the Dirac magnetic monopoles theory, especially Dirac electric/magnetic charge quantization condition. Also, we suggest a new, effective, simply called Tesla model (for analogy with positions of the solenoids by Tesla inductive motor) of the magnetic monopole instead of usual effective Dirac model (half-infinite, very tinny solenoid) of the magnetic monopole. In our, i.e. Tesla model we use three equivalent tiny solenoids connected in series with a voltage source. One end of any solenoid is placed at the circumference of a circle and solenoids are directed radial toward circle center. Length of any solenoid is a bit smaller than finite circle radius so that other end of any solenoid is very close to the circle center. Angles between neighboring solenoids equal $120^{\\circ}$. All this implies that, practically, there is no magnetic field, or, magnetic pole, e.g. $S$, in the circle center, and that whole system holds only other, $N$ magnetic pole, at the ends of the solenoids at circle circumference. Finally, we reproduce relatively satisfactory value of the fine structure constant using Planck, i.e. Bose-Einstein statistics and Wien displacement law.

Vladan Pankovic; Darko V. Kapor; Stevica Djurovic; Miodrag Krmar

2014-10-17T23:59:59.000Z

256

Theory and proposal for a quantum-degenerate electron source  

E-Print Network [OSTI]

for a quantum-degenerate electron source M. Zolotorev, E. D.propose a pulsed electron source capable of a 6D brightnesspropose a pulsed electron source with brightness approaching

Zolotorev, Max; Commins, Eugene D.; Sannibale Fernando

2006-01-01T23:59:59.000Z

257

Local dissipation effects in two-dimensional quantum Josephson junction arrays with a magnetic field  

SciTech Connect (OSTI)

We study the quantum phase transitions in two-dimensional arrays of Josephson-couples junctions with short range Josephson couplings (given by the Josephson energy E{sub J}) and the charging energy E{sub C}. We map the problem onto the solvable quantum generalization of the spherical model that improves over the mean-field theory method. The arrays are placed on the top of a two-dimensional electron gas separated by an insulator. We include effects of the local dissipation in the presence of an external magnetic flux f={phi}/{phi}{sub 0} in square lattice for several rational fluxes f=0,(1/2),(1/3),(1/4), and (1/6). We also have examined the T=0 superconducting-insulator phase boundary as a function of a dissipation {alpha}{sub 0} for two different geometry of the lattice: square and triangular. We have found a critical value of the dissipation parameter independent on geometry of the lattice and presence magnetic field.

Polak, T.P.; Kopec, T.K. [Max-Planck-Institut fuer Physik komplexer Systeme, Noethnitzer Strasse 38, 01187 Dresden (Germany); Institute for Low Temperatures and Structure Research, Polish Academy of Sciences, POB 1410, 50-950 Wroclaw 2 (Poland)

2005-07-01T23:59:59.000Z

258

Scaling Deviations for Neutrino Reactions in Aysmptotically Free Field Theories  

DOE R&D Accomplishments [OSTI]

Several aspects of deep inelastic neutrino scattering are discussed in the framework of asymptotically free field theories. We first consider the growth behavior of the total cross sections at large energies. Because of the deviations from strict scaling which are characteristic of such theories the growth need not be linear. However, upper and lower bounds are established which rather closely bracket a linear growth. We next consider in more detail the expected pattern of scaling deviation for the structure functions and, correspondingly, for the differential cross sections. The analysis here is based on certain speculative assumptions. The focus is on qualitative effects of scaling breakdown as they may show up in the X and y distributions. The last section of the paper deals with deviations from the Callan-Gross relation.

Wilczek, F. A.; Zee, A.; Treiman, S. B.

1974-11-01T23:59:59.000Z

259

Necessary and sufficient condition for a realistic theory of quantum systems  

E-Print Network [OSTI]

We study the possibility to describe pure quantum states and evens with classical probability distributions and conditional probabilities and show that the distributions and/or conditional probabilities have to assume negative values, except for a simple model whose realistic space dimension is not smaller than the Hilbert space dimension of the quantum system. This gives a negative answer to a question proposed by Montina [Phys.Rev.Lett.{\\bf 97}, 180401 (2006)] whether or not does there exist a classical theory whose phase-space dimension is much smaller than the Hilbert space dimension for any quantum system. Thus, any realistic theory of quantum mechanics with nonnegative probability distributions and conditional probabilities requires a number of variables grows exponentially with the physical size.

Zeqian Chen

2009-11-13T23:59:59.000Z

260

Perturbation Theory Based on Darboux Transformation on One-Dimensional Dirac Equation in Quantum Computation  

E-Print Network [OSTI]

We present the recent works \\cite{trisetyarso2011} on the application of Darboux transformation on one-dimensional Dirac equation related to the field of Quantum Information and Computation (QIC). The representation of physical system in one-dimensional equation and its transformation due to the Bagrov, Baldiotti, Gitman, and Shamshutdinova (BBGS)-Darboux transformation showing the possibility admitting the concept of relativity and the trade-off of concurrent condition of quantum and classical physics play into the area of QIC. The applications in cavity quantum electrodynamics and on the proposal of quantum transistor are presented.

Agung Trisetyarso

2014-11-23T23:59:59.000Z

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261

Two-field theory of incompressible-fluid turbulence  

Science Journals Connector (OSTI)

The turbulent velocity field in wave-number space is decomposed into two distinct fields. One is a purely chaotic field; while the other is a correction field, and carries all the phase information. Application of this decomposition to a thin shell of wave numbers in the dissipation range allows the elimination of modes in that shell, with the usual mode-coupling problems being circumvented by the use of a conditional average. The (conditional) mean effect of the eliminated modes appears as an increment to the viscosity, with terms of order ?2 being neglected, where ? is a dimensionless measure of bandwidth thickness, such that 0???1. An iteration (with appropriate rescaling) to successively lower shells reaches a fixed point, corresponding to a renormalized turbulent viscosity. As previously reported [W. D. McComb and A. G. Watt, Phys. Rev. Lett. 65, 3281 (1990)], the spectrum of the purely chaotic field is found to take the Kolmogorov -5/3 power-law form, with a value for the Kolmogorov spectral constant of ?=1.6, independent of ? over the range of bandwidths for which the theory is valid.

W. D. McComb and A. G. Watt

1992-10-15T23:59:59.000Z

262

Instanton calculus, topological field theories and N = 2 super Yang-Mills theories  

Science Journals Connector (OSTI)

The results obtained by Seiberg and Witten for N = 2 supersymmetric theories with gauge group SU(2) are in agreement with instanton computations carried out for winding numbers one and two. This suggests that the instanton saddle point saturates the non-perturbative contribution to the functional integral. A natural framework in which corrections to this approximation are absent is given by the topological field theory built out of the N = 2 Super Yang-Mills theory. After extending the standard construction of the Topological Yang-Mills theory to encompass the case of a non-vanishing vacuum expectation value for the scalar field, a BRST transformation is defined (as a supersymmetry plus a gauge variation), which on the instanton moduli space is the exterior derivative. We then show that each non-perturbative contribution to the N = 2 low-energy effective action can be written as the integral of a total derivative of a function of the instanton moduli. Only instanton configurations of zero conformal size contribute to this result.

Diego Bellisai; Francesco Fucito; Gabriele Travaglini; Alessandro Tanzini

2000-01-01T23:59:59.000Z

263

Atomistic force field for alumina fit to density functional theory  

SciTech Connect (OSTI)

We present a force field for bulk alumina (Al{sub 2}O{sub 3}), which has been parametrized by fitting the energies, forces, and stresses of a large database of reference configurations to those calculated with density functional theory (DFT). We use a functional form that is simpler and computationally more efficient than some existing models of alumina parametrized by a similar technique. Nevertheless, we demonstrate an accuracy of our potential that is comparable to those existing models and to DFT. We present calculations of crystal structures and energies, elastic constants, phonon spectra, thermal expansion, and point defect formation energies.

Sarsam, Joanne [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom) [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Thomas Young Centre, Imperial College London, London SW7 2AZ (United Kingdom); Finnis, Michael W.; Tangney, Paul, E-mail: p.tangney@imperial.ac.uk [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom) [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Thomas Young Centre, Imperial College London, London SW7 2AZ (United Kingdom); Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom)

2013-11-28T23:59:59.000Z

264

Neutron matter on the lattice with pionless effective field theory  

E-Print Network [OSTI]

We study neutron matter by combining pionless effective field theory with non-perturbative lattice methods. The neutron contact interaction is determined by zero temperature scattering data. We simulate neutron matter on the lattice at temperatures 4 and 8 MeV and densities below one-fifth normal nuclear matter density. Our results at different lattice spacings agree with one another and match bubble chain calculations at low densities. The equation of state of pure neutron matter obtained from our simulations agrees quantitatively with variational calculations based on realistic potentials.

Dean Lee; Thomas Schaefer

2004-12-01T23:59:59.000Z

265

Nonequilibrium transport through quantum-wire junctions and boundary defects for free massless bosonic fields  

E-Print Network [OSTI]

We consider a model of quantum-wire junctions where the latter are described by conformal-invariant boundary conditions of the simplest type in the multicomponent compactified massless scalar free field theory representing the bosonized Luttinger liquids in the bulk of wires. The boundary conditions result in the scattering of charges across the junction with nontrivial reflection and transmission amplitudes. The equilibrium state of such a system, corresponding to inverse temperature $\\beta$ and electric potential $V$, is explicitly constructed both for finite and for semi-infinite wires. In the latter case, a stationary nonequilibrium state describing the wires kept at different temperatures and potentials may be also constructed. The main result of the present paper is the calculation of the full counting statistics (FCS) of the charge and energy transfers through the junction in a nonequilibrium situation. Explicit expressions are worked out for the generating function of FCS and its large-deviations asym...

Gaw?dzki, Krzysztof

2015-01-01T23:59:59.000Z

266

Quantum Mechanics Action of ELF Electromagnetic Fields on Living Organisms  

Science Journals Connector (OSTI)

There is presently an intense discussion if extremely low frequency electromagnetic field (ELF?EMF) exposure has consequences for human health. This include exposure to structures and appliances from this range of frequency in the electromagnetic (EM) spectrum. Biological effects of such exposures have been noted frequently although the implications for specific health effects is not that clear. The basic interactions mechanisms between such fields and living matter is unknown. Numerous hypotheses have been suggested although none is convincingly supported by experimental data. Various cellular components processes and systems can be affected by EMF exposure. Since it is unlikely that EMF can induce DNA damage directly most studies have examined EMF effects on the cell membrane level general and specific gene expression and signal transduction pathways. Even more a large number of studies have been performed regarding cell proliferation cell cycle regulation cell differentiation metabolism and various physiological characteristics of cells. The aim of this letter is present the hypothesis of a possible quantum mechanic effect generated by the exposure of ELF EMF an event which is compatible with the multitude of effects observed after exposure. Based on an extensive literature review we suggest that ELF EMF exposure is able to perform such activation restructuring the electronic level of occupancy of free radicals in molecules interacting with DNA structures.

J. J. Godina?Nava

2010-01-01T23:59:59.000Z

267

A verification of quantum field theory measurement of Casimir force  

Science Journals Connector (OSTI)

Here we review our work on measurement of the Casimir force between a large aluminum coated a sphere and flat plate using an atomic force microscope. The average statistical precision is 1% of the force measur...

Anushree Roy; U Mohideen

268

Two studies of topological quantum field theory in two dimensions  

E-Print Network [OSTI]

F a generator of D b Coh(Sing(Y )). By induction, we haveby induction on dim X + dim Y . Let E be a generator of D b

Lin, Haijian Kevin

2012-01-01T23:59:59.000Z

269

Non-equilibrium Quantum Many-Body Green Function Formalism in the light of Quantum Information Theory  

E-Print Network [OSTI]

The following issues are discussed inspired by the recent paper of Kadanoff (arXiv: 1403:6162): (a) Construction of a generalized one-particle Wigner distribution (GWD) function (analog of the classical distribution function) from which the quantum kinetic equation due to Kadanoff and Baym (KB) is derived, often called the Quantum Boltzmann Equation (QBE); (b) The equation obeyed by this has a collision contribution in the form of a two-particle Green function. This term is manipulated to have Kinetic Entropy in parallel to its counterpart in the classical Boltzmann kinetic equation for the classical distribution function. This proved to be problematic in that unlike in the classical Boltzmann kinetic equation, the contribution from the kinetic entropy term was non-positive; (3) Kadanoff surmised that this situation could perhaps be related to quantum entanglement that may not have been included in his theory. It is shown that GWD is not positive everywhere (indicating dynamical quantumness) just like the commonly recognized property of the Wigner function (negative property indicating quantumness of the state). The issue of non-positive feature appearing in approximate evaluation of patently positive entities in many particle systems is here pointed to an early discussion of this issue (Phys. Rev. A10, 1852 (1974)) in terms of a theorem on truncation of cumulant expansion of a probability distribution function due to Marcinkeiwicz. The last issue of presence or absence of entanglement in an approximate evaluation of a many particle correlation poses a new problem; it is considered here in terms of fermionic entanglement theory in the light of density matrix and Green function theory of many-fermion systems. The clue comes from the fact that the Hartree-Fock approximation exhbits no entantanglement in two-particle fermion density matrix and hence also in two-particle Green function.

A. K. Rajgaopal

2014-05-12T23:59:59.000Z

270

Quantum-Gravity Phenomenology and the DSR Ether Theories  

E-Print Network [OSTI]

Guided primarily by versions of a theoretical framework called Doubly Special Relativity, or DSR, that are supposed to entail speeds of light that vary with energy while preserving the relativity of inertial frames, quantum-gravity phenomenologists have recently been seeking clues to quantum gravity, in hoped-for differing times of arrival, for light of differing energies, from cosmologically distant sources. However, it has long been known that signals, of arbitrarily high speed in opposing directions, could be used to observe the translational state of (absolute) rest, as could signals of a fixed speed different from c. Consequently, the above versions of DSR are nonviable.

Kenneth M. Sasaki

2010-09-20T23:59:59.000Z

271

Nuclear Symmetry Energy in Relativistic Mean Field Theory  

E-Print Network [OSTI]

The Physical origin of the nuclear symmetry energy is studied within the relativistic mean field (RMF) theory. Based on the nuclear binding energies calculated with and without mean isovector potential for several isobaric chains we conform earlier Skyrme-Hartree-Fock result that the nuclear symmetry energy strength depends on the mean level spacing $\\epsilon (A)$ and an effective mean isovector potential strength $\\kappa (A)$. A detaied analysis of isospin dependence of the two components contributing to the nuclear symmetry energy reveals a quadratic dependence due to the mean-isoscalar potential, $\\sim\\epsilon T^2$, and, completely unexpectedly, the presence of a strong linear component $\\sim\\kappa T(T+1+\\epsilon/\\kappa)$ in the isovector potential. The latter generates a nuclear symmetry energy in RMF theory that is proportional to $E_{sym}\\sim T(T+1)$ at variance to the non-relativistic calculation. The origin of the linear term in RMF theory needs to be further explored.

Shufang Ban; Jie Meng; Wojciech Satula; Ramon A. Wyss

2005-09-12T23:59:59.000Z

272

Spin Matrix Theory: A quantum mechanical model of the AdS/CFT correspondence  

E-Print Network [OSTI]

We introduce a new quantum mechanical theory called Spin Matrix theory (SMT). The theory is interacting with a single coupling constant g and is based on a Hilbert space of harmonic oscillators with a spin index taking values in a Lie algebra representation as well as matrix indices for the adjoint representation of U(N). We show that SMT describes N=4 super-Yang-Mills theory (SYM) near zero-temperature critical points in the grand canonical phase diagram. Equivalently, SMT arises from non-relativistic limits of N=4 SYM. Even though SMT is a non-relativistic quantum mechanical theory it contains a variety of phases mimicking the AdS/CFT correspondence. Moreover, the infinite g limit of SMT can be mapped to the supersymmetric sector of string theory on AdS_5 x S^5. We study SU(2) SMT in detail. At large N and low temperatures it is a theory of spin chains that for small g resembles planar gauge theory and for large g a non-relativistic string theory. When raising the temperature a partial deconfinement transit...

Harmark, Troels

2014-01-01T23:59:59.000Z

273

An Efficient Quantum Jump Method for Coherent Energy Transfer Dynamics in Photosynthetic Systems under the Influence of Laser Fields  

E-Print Network [OSTI]

We present a non-Markovian quantum jump approach for simulating coherent energy transfer dynamics in molecular systems in the presence of laser fields. By combining a coherent modified Redfield theory (CMRT) and a non-Markovian quantum jump (NMQJ) method, this new approach inherits the broad-range validity from the CMRT and highly efficient propagation from the NMQJ. To implement NMQJ propagation of CMRT, we show that the CMRT master equation can be casted into a generalized Lindblad form. Moreover, we extend the NMQJ approach to treat time-dependent Hamiltonian, enabling the description of excitonic systems under coherent laser fields. As a benchmark of the validity of this new method, we show that the CMRT-NMQJ method accurately describes the energy transfer dynamics in a prototypical photosynthetic complex. Finally, we apply this new approach to simulate the quantum dynamics of a dimer system coherently excited to coupled single-excitation states under the influence of laser fields, which allows us to investigate the interplay between the photoexcitation process and ultrafast energy transfer dynamics in the system. We demonstrate that laser-field parameters significantly affect coherence dynamics of photoexcitations in excitonic systems, which indicates that the photoexcitation process must be explicitly considered in order to properly describe photon-induced dynamics in photosynthetic systems. This work should provide a valuable tool for efficient simulations of coherent control of energy flow in photosynthetic systems and artificial optoelectronic materials.

Qing Ai; Yuan-Jia Fan; Bih-Yaw Jin; Yuan-Chung Cheng

2014-04-19T23:59:59.000Z

274

Theory of indirect exciton photoluminescence in elevated quantum trap  

Science Journals Connector (OSTI)

Abstract Inspired by an experiment of indirect excitons photoluminescence (PL) in elevated quantum trap (High et al., 2009), we theoretically investigate the energy relaxation and nonlinear interactions of indirect excitons in coupled quantum wells. It is shown that, when increasing the laser power, the intensity reversion of two PL peaks is due to the phonon necklace effect. In addition, we use a nonlinear Schrdinger equation including attractive two-body, repulsive three-body interactions and the excitation power dependence of energy distribution to understand the exciton states. This model gives a natural account for the PL blue shift with the increase of the excitation power. This study thus provides an alternative way to understand the underlying physics of the exciton dynamics in coupled potential wells.

C.S. Liu; T.F. Xu; Y.H. Liu; X.L. Jing

2014-01-01T23:59:59.000Z

275

The Invariant Set Postulate: A New Geometric Framework for the Foundations of Quantum Theory and the Role Played by Gravity  

E-Print Network [OSTI]

A new law of physics is proposed, defined on the cosmological scale but with significant implications for the microscale. Motivated by nonlinear dynamical systems theory and black-hole thermodynamics, the Invariant Set Postulate proposes that cosmological states of physical reality belong to a non-computable fractal state-space geometry I, invariant under the action of some subordinate deterministic causal dynamics. An exploratory analysis is made of a possible causal realistic framework for quantum physics, based on key properties of I. For example, sparseness is used to relate generic counterfactual states to points not lying on I, thus providing a geometric basis for the essential contextuality of quantum physics and the role of the abstract Hilbert Space in quantum theory. Also, self-similarity, described in a symbolic setting, provides a possible "realistic" perspective on the essential role of complex numbers and quaternions in quantum theory. A new interpretation is given to the standard "mysteries" of quantum theory: superposition, measurement, nonlocality, emergence of classicality and so on. It is proposed that heterogeneities in the fractal geometry of I are manifestations of the phenomenon of gravity. Since quantum theory is inherently blind to the existence of such state-space geometries, the analysis here suggests that attempts to formulate unified theories of physics within a conventional quantum-theoretic framework are misguided, and that a successful quantum theory of gravity should unify the causal non-Euclidean geometry of space time with the atemporal fractal geometry of state space.

T. N. Palmer

2009-06-30T23:59:59.000Z

276

A lattice bosonic model as a quantum theory of gravity Zheng-Cheng Gu  

E-Print Network [OSTI]

model on a lattice is constructed whose low energy excitations are gravitons described by linearized a quantum theory of gravity. Seven wonders of our universe: Our world has many mysteries and wonders) Identical particles. (2) Gauge interactions.1­3 (3) Fermi statistics.4,5 (4) Tiny masses of fermions ( 10

Wen, Xiao-Gang

277

Coupled-Channels Quantum Theory of Electronic Flux Density in Electronically Adiabatic Processes: Fundamentals  

Science Journals Connector (OSTI)

Coupled-Channels Quantum Theory of Electronic Flux Density in Electronically Adiabatic Processes: Fundamentals ... Ones understanding of the mechanism of this fundamental reaction, as well as those of other arguably more important electronically adiabatic processes, should be significantly advanced by a knowledge of the electronic flux density (je). ...

D. J. Diestler

2011-11-21T23:59:59.000Z

278

Split-quaternionic Hopf map, quantum Hall effect, and twistor theory  

SciTech Connect (OSTI)

Introducing a noncompact version of the Hopf map, we demonstrate remarkable close relations between quantum Hall effect and twistor theory. We first construct quantum Hall effect on a hyperboloid based on the noncompact 2nd Hopf map of split-quaternions. We analyze a hyperbolic one-particle mechanics, and explore many-body problem, where a many-body ground state wave function and membrane-like excitations are derived explicitly. In the lowest Landau level, the symmetry is enhanced from SO(3,2) to the SU(2,2) conformal symmetry. We point out that the quantum Hall effect naturally realizes the philosophy of twistor theory. In particular, emergence mechanism of fuzzy space-time is discussed somehow in detail.

Hasebe, Kazuki [Department of General Education, Kagawa National College of Technology, Takuma-cho, Mitoyo-city, Kagawa 769-1192 (Japan)

2010-02-15T23:59:59.000Z

279

Quantum Theory of Chiral Interactions in Cholesteric Liquid Crystals  

E-Print Network [OSTI]

We study the effective chiral interaction between molecules arising from quantum dispersion interactions within a model in which a) the dominant excited states of a molecule form a band whose width is small compared to the average excitation energy and b) biaxial orientational correlation between adjacent molecules can be neglected. Previous treatments of quantum chiral interactions were based on a multipole expansion of the intermolecular interaction. However, because real liquid crystals are composed of elongated molecules, we utilize an expansion in terms of only coordinates transverse to the long molecular axes. We identify two distinct physical limits depending on whether one or both of the interacting molecules are excited in the virtual state. When both molecules are excited, our results are similar to those found previously by van der Meer et al. Previously unidentified terms in which only one molecule is excited involve the interactions of local dipole moments, which exist even when the global dipole moment of the molecule vanishes. We present analytic and numerical results for helical molecules. Our results do not indicate whether the dominant chiral interaction in cholesterics results from quantum or from steric interactions.

A. S. Issaenko; A. B. Harris; T. C. Lubensky

1998-10-15T23:59:59.000Z

280

Aspects of Four Dimensional N = 2 Field Theory  

E-Print Network [OSTI]

using six dimensional method. This requires introducing irregular singularity of Hithcins equation. Compactify four dimensional theory down to three dimensions, the corresponding N = 4 theory has the interesting mirror symmetry. The mirror theory...

Xie, Dan

2011-07-11T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


281

s This article provides an overview of the field of qualitative decision theory: its motivating tasks  

E-Print Network [OSTI]

s This article provides an overview of the field of qualitative decision theory: its motivating tasks and issues, its antecedents, and its prospects. Qual- itative decision theory studies qualitative- chology, and management. T he field of decision theory and its com- panion methodology of decision

Doyle, Jon

282

On twistors and conformal field theories from six dimensions  

SciTech Connect (OSTI)

We discuss chiral zero-rest-mass field equations on six-dimensional space-time from a twistorial point of view. Specifically, we present a detailed cohomological analysis, develop both Penrose and Penrose-Ward transforms, and analyse the corresponding contour integral formulae. We also give twistor space action principles. We then dimensionally reduce the twistor space of six-dimensional space-time to obtain twistor formulations of various theories in lower dimensions. Besides well-known twistor spaces, we also find a novel twistor space amongst these reductions, which turns out to be suitable for a twistorial description of self-dual strings. For these reduced twistor spaces, we explain the Penrose and Penrose-Ward transforms as well as contour integral formulae.

Saemann, Christian [Maxwell Institute for Mathematical Sciences, Department of Mathematics, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom)] [Maxwell Institute for Mathematical Sciences, Department of Mathematics, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Wolf, Martin [Department of Mathematics, University of Surrey, Guildford GU2 7XH (United Kingdom)] [Department of Mathematics, University of Surrey, Guildford GU2 7XH (United Kingdom)

2013-01-15T23:59:59.000Z

283

Nuclear Electric Dipole Moments in Chiral Effective Field Theory  

E-Print Network [OSTI]

We provide the first consistent and complete calculation of the electric dipole moments of the deuteron, helion, and triton in the framework of chiral effective field theory. The CP-conserving and CP-violating interactions are treated on equal footing and we consider CP-violating one-, two-, and three-nucleon operators up to next-to-leading-order in the chiral power counting. In particular, we calculate for the first time EDM contributions induced by the CP-violating three-pion operator. We find that effects of CP-violating nucleon-nucleon contact interactions are larger than those found in previous studies based on phenomenological models for the CP-conserving nucleon-nucleon interactions. Our results are model-independent and can be used to test various scenarios of CP violation. As examples, we study the implications of our results on the QCD $\\theta$-term and the minimal left-right symmetric model.

Bsaisou, J; Hanhart, C; Liebig, S; Meiner, Ulf-G; Minossi, D; Nogga, A; Wirzba, A

2014-01-01T23:59:59.000Z

284

I THE THEORY OF QUANTIZED FIELDS I11 J  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

" " THE THEORY OF QUANTIZED FIELDS I11 J d i a n Schwinger i Harvard University Cambridge, Mass. I . 1 i DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency Thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement,

285

'Beyond quantum theory: a realist psycho-biological interpretation of reality' revisited  

E-Print Network [OSTI]

It is hypothesised, following Conrad et al. (1988) (http://www.tcm.phy.cam.ac.uk/~bdj10/papers/urbino.html) that quantum physics is not the ultimate theory of nature, but merely a theoretical account of the phenomena manifested in nature under particular conditions. These phenomena parallel cognitive phenomena in biosystems in a number of ways and are assumed to arise from related mechanisms. Quantum and biological accounts are complementary in the sense of Bohr and quantum accounts may be incomplete. In particular, following ideas of Stapp, 'the observer' is a system that, while lying outside the descriptive capacities of quantum mechanics, creates observable phenomena such as wave function collapse through its probing activities. Better understanding of such processes may pave the way to new science.

Brian D. Josephson

2001-05-08T23:59:59.000Z

286

On formation of equation of state of evolving quantum field  

E-Print Network [OSTI]

Stylized model of evolution of matter created in ultra relativistic heavy ion collisions is considered. Systematic procedure of computing quantum corrections in the framework of Keldysh formalism is formulated. Analytical expressions for formation of equations of state taking into account leading quantum corrections is worked out, complete description of subleasing corrections and analytical expressions for some of them is presented.

A. V. Leonidov; A. A. Radovskaya

2014-12-13T23:59:59.000Z

287

Thermodynamics and Universality for Mean Field Quantum Spin Glasses  

E-Print Network [OSTI]

We study aspects of the thermodynamics of quantum versions of spin glasses. By means of the Lie-Trotter formula for exponential sums of operators, we adapt methods used to analyze classical spin glass models to answer analogous questions about quantum models.

Nick Crawford

2006-10-13T23:59:59.000Z

288

Relationship of Quantum Entanglement to Density Functional Theory  

E-Print Network [OSTI]

The maximum von Neumann entropy principle subject to given constraints of mean values of some physical observables determines the density matrix. Similarly the stationary action principle in the case of time-dependent (dissipative) situations under similar constraints yields the density matrix. The free energy and measures of entanglement are expressed in terms of such a density matrix and thus define respective functionals of the mean values. In the light of several model calculations, it is found that the density matrix contains information about both quantum entanglement and phase transitions even though there may not be any direct relationship implied by one on the other.

A. K. Rajagopal; R. W. Rendell

2005-12-13T23:59:59.000Z

289

Microscopic Quantum Interference in the Theory of Superconductivity  

Science Journals Connector (OSTI)

...INTERPRETATION OF RECENT RESULTS ON HE-3 BELOW 3 MK - NEW LIQUID-PHASE, PHYSICAL REVIEW LETTERS...MAGNETIC PHENOMENA IN LIQUID HE-3 BELOW 3 MK, PHYSICAL REVIEW LETTERS 29 : 920 ( 1972...left). Comparison of 3.0 observed ultra-sonic attenuation with the ideal theory...

Leon N Cooper

1973-09-07T23:59:59.000Z

290

Boundary Conformal Field Theory and Ribbon Graphs: a tool for open/closed string dualities  

E-Print Network [OSTI]

We construct and fully characterize a scalar boundary conformal field theory on a triangulated Riemann surface. The results are analyzed from a string theory perspective as tools to deal with open/closed string dualities.

Mauro Carfora; Claudio Dappiaggi; Valeria L. Gili

2007-05-16T23:59:59.000Z

291

Carbon 40 (2002) 429436 Quantum-mechanical simulations of field emission from carbon  

E-Print Network [OSTI]

Carbon 40 (2002) 429­436 Quantum-mechanical simulations of field emission from carbon nanotubes *A simulations of field emission from 2-nm long open (5,5), closed (5,5) and open (10,0) carbon nanotubes recently where the carbon nanotubes [1,2], a vast literature has appeared on field-emission current from

Mayer, Alexandre

292

Development of a compact quantum cascade laser spectrometer for field measurements of CO2 isotopes  

Science Journals Connector (OSTI)

We report the development of a field-deployable, pulsed quantum cascade laser spectrometer. The instrument is designed to measure...13C/12C isotopic ratio in the CO2 released from volcanic vents. Specific 12CO2 a...

D. Weidmann; G. Wysocki; C. Oppenheimer; F.K. Tittel

2005-02-01T23:59:59.000Z

293

Structures and Quantum Conduction of Copper Nanowires under Electric Fields Using First Principles  

Science Journals Connector (OSTI)

Structures and Quantum Conduction of Copper Nanowires under Electric Fields Using First Principles ... Key Laboratory of Automobile Materials (Jilin University), Ministry of Education, and Department of Materials Science and Engineering, Jilin University, Changchun 130022, China ...

C. He; P. Zhang; Y. F. Zhu; Q. Jiang

2008-05-22T23:59:59.000Z

294

Quantum Theory of ?erenkov Radiation, Spectral Cutoff and Resonances  

E-Print Network [OSTI]

We show that the well-established \\v{C}erenkov Effect contains new phenomena arising directly from the quantum nature of the charged particles. These include large deviations from the classically-expected radiation intensity and angle. Most importantly, we find that the traditional Cerenkov angle splits, confining the emitted radiation into two distinctive cones into which two photonic shock waves are emitted. Interestingly, one of the two shockwaves can move on a backward cone, which is otherwise considered impossible for \\v{C}erenkov Radiaiton in ordinary materials. Moreover, for specific values of the particle momentum, we predict an upper frequency cutoff in the photon emission. Surprisingly, for this extremum frequency we find a diverging rate of photon emission, implying this is a new resonant light-matter interaction. Some of these new effects cannot be found without the full quantum derivation. Importantly, our findings are observable for electron beams with realistic parameters, offering new applications including coherent x-ray sources and open a new realm for \\v{C}erenkov detectors.

Ido Kaminer; Maor Mutzafi; Gal Harari; Hanan Herzig Sheinfux; Amir Levy; Scott Skirlo; Jonathan Nemirovsky; John D. Joannopoulos; Mordechai Segev; Marin Solja?i?

2014-11-01T23:59:59.000Z

295

Time in quantum mechanics  

E-Print Network [OSTI]

OF CONTENTS I. INTRODUCTION II. HISTORICAL DEVELOPMENT A. Classical Mechanics B. Quantum Theory . C. The Problem 3 4 6 III. TIME ATOMS AND DISCRETE TIME A. The Earliest Applications of Atomistic and Discrete Time . . . . . B. The Radiating Electron... . C. Quantum Field Theory 8 10 l2 IV. TIME OPERATOR FORMULATIONS 16 A. Advocates Against a Time Operator . B. The Possibility of a Time Operator C, Advocates in Favor of a Time Operator D. A Restricted Time Delay Operator: Scattering Theory...

Chapin, Kimberly R.

2012-06-07T23:59:59.000Z

296

Dimensional reduction and quantum-to-classical reduction at high temperatures  

Science Journals Connector (OSTI)

We discuss the relation between dimensional reduction in quantum field theories at finite temperature and a familiar quantum-mechanical phenomenon that quantum effects become negligible at high temperatures. Fermi and Bose fields are compared in this respect. We show that decoupling of fermions from the dimensionally reduced theory can be related to the nonexistence of classical statistics for a Fermi field.

M. A. Stephanov

1995-09-15T23:59:59.000Z

297

Simulations of magnetic field gradients due to micro-magnets on a triple quantum dot circuit  

SciTech Connect (OSTI)

To quantify the effects of local magnetic fields on triple quantum dots, the Heisenberg Hamiltonian has been diagonalized for three electrons coupled via the exchange interaction. In particular, we have investigated different geometries of micro-magnets located on top of the triple dot in order to optimize the field gradient characteristics. In this paper, we focus on two geometries which are candidates for an addressable EDSR triple quantum dot device.

Poulin-Lamarre, G. [National Research Council of Canada, Ottawa, On., Canada, K1A-0R6 and Dpartement de physique, Universit de Sherbrooke, Sherbrooke, Qc. J1K-2R1 (Canada); Bureau-Oxton, C. [Dpartement de physique, Universit de Sherbrooke, Sherbrooke, Qc. J1K-2R1 (Canada); Kam, A. [National Research Council of Canada, Ottawa, On. K1A-0R6 (Canada); Zawadzki, P.; Aers, G. [National Research Council of Canada, Ottawa, On. K1A-0R6 (Canada); Studenikin, S. [National Research Council of Canada, Ottawa, On.K1A-0R6 (Canada); Pioro-Ladrire, M. [Dpartement de physique, Universit de Sherbrooke, Sherbrooke, Qc. J1K-2R1 (Canada); Sachrajda, A. S. [National Research Council of Canada, Ottawa, On., Canada, K1A-0R6 and Dpartement de physique, Universit de Sherbrooke, Sherbrooke, Qc. J1K-2R1 (Canada)

2013-12-04T23:59:59.000Z

298

Density-functional theory of freezing of quantum liquids at zero temperature using exact liquid-state linear response  

E-Print Network [OSTI]

Density-functional theory of freezing of quantum liquids at zero temperature using exact liquid the shortcomings of the currently popular density-functional approximate theories to describe 3d freezing distances. S0163-1829 97 04310-5 I. INTRODUCTION The modern density-functional theory DFT , which

Likos, Christos N.

299

A novel Artificial Neural Network training method combined with Quantum Computational Multi-Agent System theory  

Science Journals Connector (OSTI)

Artificial Neural Networks (ANNs) are powerful tools that can be used to model and investigate various complex and non-linear phenomena. In this study, we construct a new ANN, which is based on Multi-Agent System (MAS) theory and quantum computing algorithm. All nodes in this new ANN are presented as Quantum Computational (QC) agents, and these agents have learning ability. A novel ANN training method was proposed via implementing QCMAS reinforcement learning. This new ANN has powerful parallel-work ability and its training time is shorter than classic algorithm. Experiment results show that this method is effective.

Xiangping Meng; Jianzhong Wang; Yuzhen Pi; Quande Yuan

2009-01-01T23:59:59.000Z

300

A quantum-dynamical theory for nonlinear optical interactions in graphene  

E-Print Network [OSTI]

We use a quantum-dynamical model to investigate the optical response of graphene under low excitation power. Ultrafast carrier relaxation processes, which play an important role for understanding the optical response of graphene, are included phenomenologically into the model. We obtain analytical solutions for the linear and third-order nonlinear optical response of graphene, and four-wave mixing in particular. This theory shows agreement with recently reported experimental data on linear complex optical conductivity and four-wave mixing, providing evidence for ultrafast quantum-dephasing times of approximately 1 fs.

Zheshen Zhang; Paul L. Voss

2011-06-23T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


301

High Field Quantum Spin Hall State in Graphene  

Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)

quantum spin Hall (QSH) state-the paradigmatic two dimensional SPT phase-in monolayer graphene. In a QSH state, electrons with opposite spin polarization carry current in opposite...

302

Coherence Momentum in Second-Order Vectorial Coherence Theory of Stationary Electromagnetic Fields  

Science Journals Connector (OSTI)

In analog to the electromagnetic momentum, we introduce vector and tensor densities to the general coherence theory of vector electromagnetic fields, and present new conservation...

Wang, Wei; Takeda, Mitsuo

303

Coherence Momentum in Second-Order Vectorial Coherence Theory of Stationary Electromagnetic Fields  

Science Journals Connector (OSTI)

In analog to the electromagnetic momentum, we introduce vector and tensor densities to the general coherence theory of vector electromagnetic fields, and present new conservation laws...

Wang, Wei; Takeda, Mitsuo

304

Parity Violation in Neutron Deuteron Scattering in Pionless Effective Field Theory.  

E-Print Network [OSTI]

??In this dissertation the parity violating neutron deuteron scattering amplitudes are calculated using pionless effective field theory to leading order. The five low energy parity (more)

Vanasse, Jared James

2012-01-01T23:59:59.000Z

305

Quantum theory of operation for rectenna solar cells  

Science Journals Connector (OSTI)

Optical rectennas, sub-micrometre antenna-coupled diodes, can directly rectify solar and thermal electromagnetic radiation, and have been proposed as an alternative to conventional semiconductor photovoltaics. We develop a comprehensive description of the operating principle of rectenna solar cells. In prior work classical concepts from microwave rectenna theory have been applied to the analysis of photovoltaic power generation using these ultra-high frequency rectifiers. Because of their high photon energy the interaction of petahertz frequency waves with fast-responding diodes requires a semiclassical analysis. We use the theory of photon-assisted transport to derive the currentvoltage [I(V)] characteristics of metal/insulator/metal tunnel diodes under illumination. We show how power is generated in the second quadrant of the I(V) characteristic, derive solar cell parameters, and analyse the key variables that influence the performance under monochromatic radiation and to a first order approximation. The efficiency improves with reduced dark current under reverse bias and increasing incident electromagnetic power.

Sachit Grover; Saumil Joshi; Garret Moddel

2013-01-01T23:59:59.000Z

306

On geometry influence on the behavior of a quantum mechanical scalar particle with intrinsic structure in external magnetic and electric fields  

E-Print Network [OSTI]

Relativistic theory of the Cox's scalar not point-like particle with intrinsic structure is developed on the background of arbitrary curved space-time. It is shown that in the most general form, the extended Proca-like tensor first order system of equations contains non minimal interaction terms through electromagnetic tensor F_{\\alpha \\beta} and Ricci tensor R_{\\alpha \\beta}. In relativistic Cox's theory, the limiting procedure to non-relativistic approximation is performed in a special class of curved space-time models. This theory is specified in simple geometrical backgrounds: Euclid's, Lobachevsky's, and Rie\\-mann's. Wave equation for the Cox's particle is solved exactly in presence of external uniform magnetic and electric fields in the case of Minkowski space. Non-trivial additional structure of the particle modifies the frequency of a quantum oscillator arising effectively in presence if external magnetic field. Extension of these problems to the case of the hyperbolic Lobachevsky space is examined. In presence of the magnetic field, the quantum problem in radial variable has been solved exactly; the quantum motion in z-direction is described by 1-dimensional Schr\\"{o}dinger-like equation in an effective potential which turns out to be too difficult for analytical treatment. In the presence of electric field, the situation is similar. The same analysis has been performed for spherical Riemann space model.

O. V. Veko; K. V. Kazmerchuk; E. M. Ovsiyuk; V. V. Kisel; V. M. Red'kov

2014-11-07T23:59:59.000Z

307

Mean- Field Approximation and a Small Parameter in Turbulence Theory  

E-Print Network [OSTI]

Numerical and physical experiments on two-dimensional (2d) turbulence show that the differences of transverse components of velocity field are well described by a gaussian statistics and Kolmogorov scaling exponents. In this case the dissipation fluctuations are irrelevant in the limit of small viscosity. In general, one can assume existence of critical space-dimensionality $d=d_{c}$, at which the energy flux and all odd-order moments of velocity difference change sign and the dissipation fluctuations become dynamically unimportant. At $d', leading to the observed gaussian statistics and Kolmogorov scaling of transverse velocity differences. It is shown that in the vicinity of $d=d_{c}$ the ratio of the relaxation and translation characteristic times decreases to zero, thus giving rise to a small parameter of the theory. The expressions for pressure and dissipation contributions to the exact equation for the generating function of transverse velocity differences are derived in the vicinity of $d=d_{c}$. The resulting equation describes experimental data on two-dimensional turbulence and demonstrate onset of intermittency as $d-d_{c}>0$ and $r/L\\to 0$ in three-dimensional flows in close agreement with experimental data. In addition, some new exact relations between correlation functions of velocity differences are derived. It is also predicted that the single-point pdf of transverse velocity difference in developing as well as in the large-scale stabilized two-dimensional turbulence is a gaussian.

Victor Yakhot

2000-01-13T23:59:59.000Z

308

Proton-Proton Weak Capture in Chiral Effective Field Theory  

SciTech Connect (OSTI)

The astrophysical $S$-factor for proton-proton weak capture is calculated in chiral effective field theory over the center-of-mass relative-energy range 0--100 keV. The chiral two-nucleon potential derived up to next-to-next-to-next-to leading order is augmented by the full electromagnetic interaction including, beyond Coulomb, two-photon and vacuum-polarization corrections. The low-energy constants (LEC's) entering the weak current operators are fixed so as to reproduce the $A=3$ binding energies and magnetic moments, and the Gamow-Teller matrix element in tritium $\\beta$ decay. Contributions from $S$ and $P$ partial waves in the incoming two-proton channel are retained. The $S$-factor at zero energy is found to be $S(0)=(4.030 \\pm 0.006)\\times 10^{-23}$ MeV fm$^2$, with a $P$-wave contribution of $0.020\\times 10^{-23}$ MeV fm$^2$. The theoretical uncertainty is due to the fitting procedure of the LEC's and to the cutoff dependence. It is shown that polynomial fits to parametrize the energy dependence of the $S$-factor are inherently unstable.

Marcucci, Laura Elisa [Pisa U., INFN-Pisa; Schiavilla, Rocco [Old Dominion U., JLAB; Viviani, MIchele [INFN-Pisa

2013-05-01T23:59:59.000Z

309

Theory of Multiple-Quantum Transitions in the Ground State of K30  

Science Journals Connector (OSTI)

The results of an earlier paper are applied to magnetic resonance transitions in the ground state of K39. Formulas are obtained for the parameters characterizing single- and multiple-quantum transitions, and the values of these parameters are calculated for a Zeeman field corresponding to x=0.21135.

Harold Salwen

1956-01-15T23:59:59.000Z

310

Magnetic-Field Induced Quantum Phase Transitions in Triangular-Lattice Antiferromagnets  

E-Print Network [OSTI]

Magnetic-Field Induced Quantum Phase Transitions in Triangular-Lattice Antiferromagnets T Ono1, H Department of Physics, Smith College, Northampton, Massachusetts 01063, USA 5 National High Magnetic Field are magnetically described as quasi-two-dimensional triangular-lattice antiferromagnets with spin-1 2 and 1

McQuade, D. Tyler

311

Quantum calculations of correlated electron-ion collisions in a strong laser field  

E-Print Network [OSTI]

Quantum calculations of correlated electron-ion collisions in a strong laser field G. Rascol, H September 2006; published online 31 October 2006 The energy spectrum and angular distribution of electrons scattered by an ion in a strong laser field are investigated as a function of the incident electron velocity

Kull, Hans-Jörg

312

Double wells, scalar fields and quantum phase transitions in ions traps  

E-Print Network [OSTI]

Since Hund's work on the ammonia molecule, the double well potential has formed a key paradigm in physics. Its importance is further underlined by the central role it plays in the Landau theory of phase transitions. Recently, the study of entanglement properties of many-body systems has added a new angle to the study of quantum phase transitions of discrete and continuous degrees of freedom, i.e., spin and harmonic chains. Here we show that control of the radial degree of freedom of trapped ion chains allows for the simulation of linear and non-linear Klein-Gordon fields on a lattice, in which the parameters of the lattice, the non-linearity and mass can be controlled at will. The system may be driven through a phase transition creating a double well potential between different configurations of the ion crystal. The dynamics of the system are controllable, local properties are measurable and tunnelling in the double well potential would be observable.

A. Retzker; R. Thompson; D. Segal; M. B. Plenio

2008-01-04T23:59:59.000Z

313

Thermodynamics and Finite size scaling in Scalar Field Theory  

E-Print Network [OSTI]

In this work we consider the 1-component real scalar $\\phi^4$ theory in 4 space-time dimensions on the lattice and investigate the finite size scaling of thermodynamic quantities to study whether the thermodynamic limit is attained. The results are obtained for the symmetric phase of the theory.

Debasish Banerjee; Saumen Datta; Sourendu Gupta

2008-12-05T23:59:59.000Z

314

Electric field control of spin-resolved edge states in graphene quantum nanorings  

SciTech Connect (OSTI)

The electric-field effect on the electronic and magnetic properties of triangular and hexagonal graphene quantum rings with zigzag edge termination is investigated by means of the single-band tight-binding Hamiltonian and the mean-field Hubbard model. It is shown how the electron and spin states in the nanoring structures can be manipulated by applying an electric field. We find different spin-depolarization behaviors with variation of electric field strength due to the dependence of spin densities on the shapes and edges of this kind of nanorings. In the case of triangular quantum rings, the magnetization on the inner and outer edges can be selectively tuned and the spin states depolarize gradually as the field strength is increased, while in the case of hexagonal nanorings, the transverse electric field reduces the magnetic moments on both inner and outer edges symmetrically and rapidly.

Farghadan, R., E-mail: rfarghadan@kashanu.ac.ir [Department of Physics, University of Kashan, Kashan (Iran, Islamic Republic of); Saffarzadeh, A. [Department of Physics, Payame Noor University, P.O. Box 19395-3697, Tehran (Iran, Islamic Republic of); Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6 (Canada)

2014-05-07T23:59:59.000Z

315

Field theory: Why have some physicists abandoned it?  

Science Journals Connector (OSTI)

...microscopic distances or at energies of a few electron...conceptual and technical obstacles: quantum...actual orbits in the solar system, when appropriate...to overcome these two obstacles only when the models...breaking, which relies on energy differences between...

Roman Jackiw

1998-01-01T23:59:59.000Z

316

Dynamics of interacting phantom scalar field dark energy in Loop Quantum Cosmology  

E-Print Network [OSTI]

We study the dynamics of a phantom scalar field dark energy interacting with dark matter in loop quantum cosmology (LQC). Two kinds of coupling of the form $\\alpha{\\rho_m}{\\dot\\phi}$ (case I) and $3\\beta H (\\rho_\\phi +\\rho_m)$ (case II) between the phantom energy and dark matter are examined with the potential for the phantom field taken to be exponential. For both kinds of interactions, we find that the future singularity appearing in the standard FRW cosmology can be avoided by loop quantum gravity effects. In case II, if the phantom field is initially rolling down the potential, the loop quantum effect has no influence on the cosmic late time evolution and the universe will accelerate forever with a constant energy ratio between the dark energy and dark matter.

Fu, Xiangyun; Wu, Puxun

2008-01-01T23:59:59.000Z

317

$^6$He nucleus in halo effective field theory  

E-Print Network [OSTI]

Background: In recent years properties of light rare isotopes have been measured with high accuracy. At the same time, the theoretical description of light nuclei has made enormous progress, and properties of, e.g., the Helium isotopes can now be calculated {\\it ab initio}. These advances make those rare isotopes an ideal testing ground for effective field theories (EFTs) built upon cluster degrees of freedom. Purpose: Systems with widely separated intrinsic scales are well suited to an EFT treatment. The Borromean halo nucleus $^6$He exhibits such a separation of scales. In this work an EFT in which the degrees of freedom are the valence neutrons ($n$) and an inert $^4$He-core ($\\alpha$) is employed. The properties of ${}^6$He can then be calculated using the momentum-space Faddeev equations for the $\\alpha nn$ bound state to obtain information on ${}^6$He at leading order (LO) within the EFT. Results: The $nn$ virtual state and the $^2$P$_{3/2}$ resonance in $^5$He give the two-body amplitudes which are input to our LO three-body Halo EFT calculation. We find that without a genuine three-body interaction the two-neutron separation energy $S_{2n}$ of ${}^6$He is strongly cutoff dependent. We introduce a $nn \\alpha$ "three-body" operator which renormalizes the system, adjusting its coefficient to reproduce the $S_{2n}$ of $^6$He. The Faddeev components are then cutoff independent for cutoffs of the order of, and above, the breakdown scale of the Halo EFT. Conclusions: As in the case of a three-body system where only resonant s-wave interactions are present, one three-body input is required for the renormalization of the EFT equations that describe $^6$He at LO. However, in contrast to the s-wave-only case, the running of the LO $nn\\alpha$ counterterm does not exhibit discrete scale invariance, due to the presence of the p-wave $n\\alpha$ interaction.

C. Ji; Ch. Elster; D. R. Phillips

2014-11-03T23:59:59.000Z

318

Conformal field theories at non-zero temperature: operator product expansions, Monte Carlo, and holography  

E-Print Network [OSTI]

We compute the non-zero temperature conductivity of conserved flavor currents in conformal field theories (CFTs) in 2+1 spacetime dimensions. At frequencies much greater than the temperature, $\\hbar\\omega>> k_B T$, the $\\omega$ dependence can be computed from the operator product expansion (OPE) between the currents and operators which acquire a non-zero expectation value at T > 0. Such results are found to be in excellent agreement with quantum Monte Carlo studies of the O(2) Wilson-Fisher CFT. Results for the conductivity and other observables are also obtained in vector 1/N expansions. We match these large $\\omega$ results to the corresponding correlators of holographic representations of the CFT: the holographic approach then allows us to extrapolate to small $\\hbar \\omega/(k_B T)$. Other holographic studies implicitly only used the OPE between the currents and the energy-momentum tensor, and this yields the correct leading large $\\omega$ behavior for a large class of CFTs. However, for the Wilson-Fisher ...

Katz, Emanuel; Sorensen, Erik S; Witczak-Krempa, William

2014-01-01T23:59:59.000Z

319

Conformal field theories at non-zero temperature: operator product expansions, Monte Carlo, and holography  

E-Print Network [OSTI]

We compute the non-zero temperature conductivity of conserved flavor currents in conformal field theories (CFTs) in 2+1 spacetime dimensions. At frequencies much greater than the temperature, $\\hbar\\omega>> k_B T$, the $\\omega$ dependence can be computed from the operator product expansion (OPE) between the currents and operators which acquire a non-zero expectation value at T > 0. Such results are found to be in excellent agreement with quantum Monte Carlo studies of the O(2) Wilson-Fisher CFT. Results for the conductivity and other observables are also obtained in vector 1/N expansions. We match these large $\\omega$ results to the corresponding correlators of holographic representations of the CFT: the holographic approach then allows us to extrapolate to small $\\hbar \\omega/(k_B T)$. Other holographic studies implicitly only used the OPE between the currents and the energy-momentum tensor, and this yields the correct leading large $\\omega$ behavior for a large class of CFTs. However, for the Wilson-Fisher CFT a relevant "thermal" operator must also be considered, and then consistency with the Monte Carlo results is obtained without a previously needed ad hoc rescaling of the T value. We also establish sum rules obeyed by the conductivity of a wide class of CFTs.

Emanuel Katz; Subir Sachdev; Erik S. Sorensen; William Witczak-Krempa

2014-09-12T23:59:59.000Z

320

? dependence of the scalar field in Brans-Dicke theory  

Science Journals Connector (OSTI)

This article examines the claim that the Brans-Dicke scalar field ???0+O(1/?) for large ? when the matter field is traceless. It is argued that such a claim cannot be true in general.

A. Bhadra and K. K. Nandi

2001-09-25T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
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321

Nested Quantum Error Correction Codes  

E-Print Network [OSTI]

The theory of quantum error correction was established more than a decade ago as the primary tool for fighting decoherence in quantum information processing. Although great progress has already been made in this field, limited methods are available in constructing new quantum error correction codes from old codes. Here we exhibit a simple and general method to construct new quantum error correction codes by nesting certain quantum codes together. The problem of finding long quantum error correction codes is reduced to that of searching several short length quantum codes with certain properties. Our method works for all length and all distance codes, and is quite efficient to construct optimal or near optimal codes. Two main known methods in constructing new codes from old codes in quantum error-correction theory, the concatenating and pasting, can be understood in the framework of nested quantum error correction codes.

Zhuo Wang; Kai Sun; Hen Fan; Vlatko Vedral

2009-09-28T23:59:59.000Z

322

Physics as Information Theory  

SciTech Connect (OSTI)

The experience from Quantum Information of the last twenty years has lead theorists to look at Quantum Theory and the whole of Physics from a different angle. A new information-theoretic paradigm is emerging, long time ago prophesied by John Archibald Wheeler with his popular coinage 'It from bit'. Theoretical groups are now addressing the problem of deriving Quantum Theory from informational principles, and similar lines are investigated in new approaches to Quantum Gravity. In my talk I will review some recent advances on these lines. The general idea synthesizing the new paradigm is that there is only Quantum Theory (without quantization rules): the whole Physics--including space-time and relativity--is emergent from quantum-information processing. And, since Quantum Theory itself is made with purely informational principles, the whole Physics must be reformulated in information-theoretical terms. The review is divided into the following parts: (a) The informational axiomatization of Quantum Theory; (b) How space-time and relativistic covariance emerge from the quantum computation; (c) What is the information-theoretical meaning of inertial mass and Planck constant, and how the quantum field emerges; (d) Observational consequences: mass-dependent refraction index of vacuum. I then conclude with some possible future research lines.

D'Ariano, Giacomo Mauro (University of Pavia) [University of Pavia

2010-10-20T23:59:59.000Z

323

Topics in N = 1 supergravity in four dimensions and superstring effective field theories beyond tree-level  

SciTech Connect (OSTI)

In this thesis, the author presents some works in the direction of studying quantum effects in locally supersymmetric effective field theories that appear in the low energy limit of superstring theory. After reviewing the Kaehler covariant formulation of supergravity, he shows the calculation of the divergent one-loop contribution to the effective boson Lagrangian for supergravity, including the Yang-Mills sector and the helicity-odd operators that arise from integration over fermion fields. The only restriction is on the Yang-Mills kinetic energy normalization function, which is taken diagonal in gauge indices, as in models obtained from superstrings. He then presents the full result for the divergent one-loop contribution to the effective boson Lagrangian for supergravity coupled to chiral and Yang-Mills supermultiplets. He also considers the specific case of dilaton couplings in effective supergravity Lagrangians from superstrings, for which the one-loop result is considerably simplified. He studies gaugino condensation in the presence of an intermediate mass scale in the hidden sector. S-duality is imposed as an approximate symmetry of the effective supergravity theory. Furthermore, the author includes in the Kaehler potential the renormalization of the gauge coupling and the one-loop threshold corrections at the intermediate scale. It is shown that confinement is indeed achieved. Furthermore, a new running behavior of the dilaton arises which he attributes to S-duality. He also discusses the effects of the intermediate scale, and possible phenomenological implications of this model.

Saririan, K.

1997-05-01T23:59:59.000Z

324

The harmonic oscillator with dissipation within the theory of open quantum systems  

E-Print Network [OSTI]

Time evolution of the expectation values of various dynamical operators of the harmonic oscillator with dissipation is analitically obtained within the framework of the Lindblad theory for open quantum systems. We deduce the density matrix of the damped harmonic oscillator from the solution of the Fokker-Planck equation for the coherent state representation, obtained from the master equation for the density operator. The Fokker-Planck equation for the Wigner distribution function, subject to either the Gaussian type or the $\\delta$-function type of initial conditions, is also solved by using the Wang-Uhlenbeck method. The obtained Wigner functions are two-dimensional Gaussians with different widths.

A. Isar

2005-08-18T23:59:59.000Z

325

Reliability of the Optimized Perturbation Theory for scalar fields at finite temperature  

SciTech Connect (OSTI)

The thermodynamics of a massless scalar field with a quartic interaction is studied up to third order in the Optimized Perturbation Theory (OPT) method. A comparison with other nonperturbative approaches is performed such that the reliability of OPT is accessed.

Farias, R. L.; Teixeira, D. L. Jr. [Departamento de Ciencias Naturais, Universidade Federal de Sao Joao del Rei, 36301-000 Sao Joao del Rei, MG (Brazil); Ramos, R. O. [Departamento de Fisica Teorica, Universidade do Estado do Rio de Janeiro, 20550-013 Rio de Janeiro, RJ (Brazil)

2013-03-25T23:59:59.000Z

326

Symmetry energy, neutron skin, and neutron star radius from chiral effective field theory interactions  

E-Print Network [OSTI]

We discuss neutron matter calculations based on chiral effective field theory interactions and their predictions for the symmetry energy, the neutron skin of 208 Pb, and for the radius of neutron stars.

K. Hebeler; A. Schwenk

2014-01-22T23:59:59.000Z

327

Knot and Conformal Field Theory Approach in Molecular and Nuclear Physics  

Science Journals Connector (OSTI)

......Field Theory Approach in Molecular and Nuclear Physics Syurei Iwao Department of...problem of dissociation (binding) energy for the molecules (nuclei) is discussed...13) Ring P. , Schuck P., The Nuclear Many-Body Problem (1980) : Springer......

Syurei Iwao

1990-03-01T23:59:59.000Z

328

Lattice Boltzmann method for multiscale self-consistent field theory simulations of block copolymers  

E-Print Network [OSTI]

A new Lattice Boltzmann (LB) approach is introduced to solve for the block copolymer propagator in polymer field theory. This method bridges two desired properties from different numerical techniques, namely: (i) it is ...

Chen, Hsieh

329

Modeling of strained quantum wires using eight-band k?p theory  

Science Journals Connector (OSTI)

We have calculated numerically the one-dimensional band structure and densities of states of a V-shaped In0.2Ga0.8As/AlxGa1-xAs single quantum wire using eight-band k?p theory. A finite-difference scheme is used for the calculations. The model includes the realistic orientation, shape, material composition, strain distribution, and piezoelectric charging of the wire. We find a dominant impact of the piezoelectric potential on the band structure and a marked spin splitting of the valence bands. Also, the conduction band is strongly nonparabolic. We propose an efficient procedure to calculate interior eigenvectors from Hamiltonians including conduction-bandvalence-band interactions. This algorithm is 2090 times faster than the best prevailing method and also applies to other Hamiltonians for the modeling of nanostructures, including those occurring in tight-binding or pseudopotential theory.

O. Stier and D. Bimberg

1997-03-15T23:59:59.000Z

330

Quantum theory of large amplitude collective motion and the Born-Oppenheimer method  

E-Print Network [OSTI]

We study the quantum foundations of a theory of large amplitude collective motion for a Hamiltonian expressed in terms of canonical variables. In previous work the separation into slow and fast (collective and non-collective) variables was carried out without the explicit intervention of the Born Oppenheimer approach. The addition of the Born Oppenheimer assumption not only provides support for the results found previously in leading approximation, but also facilitates an extension of the theory to include an approximate description of the fast variables and their interaction with the slow ones. Among other corrections, one encounters the Berry vector and scalar potential. The formalism is illustrated with the aid of some simple examples, where the potentials in question are actually evaluated and where the accuracy of the Born Oppenheimer approximation is tested. Variational formulations of both Hamiltonian and Lagrangian type are described for the equations of motion for the slow variables.

Abraham Klein; Niels R. Walet

1993-03-20T23:59:59.000Z

331

Quantum stochastic calculus approach to modeling double-pass atom-field coupling  

Science Journals Connector (OSTI)

We examine a proposal by Sherson and Mlmer to generate polarization-squeezed light in terms of quantum stochastic calculus (QSC). We investigate the statistics of the output field and confirm their results using the QSC formalism. In addition, we study the atomic dynamics of the system and find that this setup can produce up to 3 dB of atomic spin squeezing.

Gopal Sarma; Andrew Silberfarb; Hideo Mabuchi

2008-08-07T23:59:59.000Z

332

Bose Glass of Quasiparticles in Doped Quantum Magnet Gregory S. Boebinger, National High Magnetic Field Laboratory  

E-Print Network [OSTI]

Bose Glass of Quasiparticles in Doped Quantum Magnet Gregory S. Boebinger, National High Magnetic. This BEC can localize in the presence of disorder caused by Br- doping to form a Bose Glass. The BEC-Bose Glass (BEC-BG) transition can be carefully controlled by magnetic field, allowing us to sensitively

Weston, Ken

333

Echo of the Quantum Bounce  

E-Print Network [OSTI]

We identify a signature of quantum gravitational effects that survives from the early universe to the current era: Fluctuations of quantum fields as seen by comoving observers are significantly influenced by the history of the early universe. In particular we show how the existence (or not) of a quantum bounce leaves a trace in the background quantum noise that is not damped and would be non-negligible even nowadays. Furthermore, we estimate an upper bound for the typical energy and length scales where quantum effects are relevant. We discuss how this signature might be observed and therefore used to build falsifiability tests of quantum gravity theories.

Luis J. Garay; Mercedes Martin-Benito; Eduardo Martin-Martinez

2014-02-15T23:59:59.000Z

334

Existence of solutions for Hamiltonian field theories by the Hamilton-Jacobi technique  

SciTech Connect (OSTI)

The paper is devoted to prove the existence of a local solution of the Hamilton-Jacobi equation in field theory, whence the general solution of the field equations can be obtained. The solution is adapted to the choice of the submanifold where the initial data of the field equations are assigned. Finally, a technique to obtain the general solution of the field equations, starting from the given initial manifold, is deduced.

Bruno, Danilo [Dipartimento di Matematica dell'Universita di Genova Via Dodecaneso, 35-16146 Genova (Italy)

2011-01-15T23:59:59.000Z

335

Mean Field Theory of Josephson Junction Arrays with Charge Frustration  

E-Print Network [OSTI]

Using the path integral approach, we provide an explicit derivation of the equation for the phase boundary for quantum Josephson junction arrays with offset charges and non-diagonal capacitance matrix. For the model with nearest neighbor capacitance matrix and uniform offset charge $q/2e=1/2$, we determine, in the low critical temperature expansion, the most relevant contributions to the equation for the phase boundary. We explicitly construct the charge distributions on the lattice corresponding to the lowest energies. We find a reentrant behavior even with a short ranged interaction. A merit of the path integral approach is that it allows to provide an elegant derivation of the Ginzburg-Landau free energy for a general model with charge frustration and non-diagonal capacitance matrix. The partition function factorizes as a product of a topological term, depending only on a set of integers, and a non-topological one, which is explicitly evaluated.

G. Grignani; A. Mattoni; P. Sodano; A. Trombettoni

1999-02-12T23:59:59.000Z

336

Radiative lifetime of barbell excitons in semiparabolic double quantum wells under intense laser fields  

Science Journals Connector (OSTI)

Abstract The binding energy and optical properties of barbell excitons in GaAsGa1?xAlxAs semiparabolic double quantum wells under intense laser fields are investigated. Calculations are performed within the effective mass and envelope-function approximations, including the conduction band nonparabolicity. The dependence of the binding energy, oscillator strength and exciton absorption spectrum on the laser field in symmetric and asymmetric quantum wells is studied by using a finite difference method. It is shown that the exciton radiative lifetime can be tuned to a large extent by a proper choice of the structure design (double well size, middle barrier position and its thickness) as well as by varying the laser field intensity.

E.C. Niculescu

2013-01-01T23:59:59.000Z

337

Effective field theory, three-loop perturbative expansion, and their experimental implications in graphene many-body effects  

E-Print Network [OSTI]

Many-body electron-electron interaction effects are theoretically considered in monolayer graphene from a continuum effective field-theoretic perspective by going beyond the standard leading-order perturbative renormalization group (RG) analysis. Given that the bare fine structure constant in graphene is of order unity, which is neither small to justify a perturbative expansion nor large enough for strong-coupling theories to be applicable, the problem is a difficult one, with some similarity to 2+1-dimensional strong-coupling quantum electrodynamics (QED). In this work, we take a systematic and comprehensive analytical approach, working primarily at the Dirac point (intrinsic graphene), by going up to three loops in the diagrammatic expansion to both ascertain the validity of perturbation theory and to estimate quantitatively higher-order renormalization effects. While no direct signatures for non-Fermi liquid behavior at the Dirac point have yet been observed experimentally, there is ample evidence for the interaction-induced renormalization of the graphene velocity as the carrier density approaches zero. We provide a critical comparison between theory and experiment, using both bare- and screened-interaction (RPA) calculations. We find that while the one-loop RG analysis gives reasonable agreement with the experimental data, especially when screening and finite-density effects are included through the RPA, the two-loop analysis reveals a strong-coupling critical point in suspended graphene, signifying either a quantum phase transition or a breakdown of the weak-coupling RG approach. We show that the latter is more likely by adapting Dyson's argument for the breakdown of perturbative QED to the case of graphene. We propose future experiments and theoretical directions to make further progress on this important and difficult problem.

Edwin Barnes; E. H. Hwang; R. E. Throckmorton; S. Das Sarma

2014-01-27T23:59:59.000Z

338

Two charges on plane in a magnetic field: II. Moving neutral quantum system across a magnetic field  

E-Print Network [OSTI]

The moving neutral system of two Coulomb charges on a plane subject to a constant magnetic field $B$ perpendicular to the plane is considered. It is shown that the composite system of finite total mass is bound for any center-of-mass momentum $P$ and magnetic field strength; the energy of the ground state is calculated accurately using a variational approach. Their accuracy is cross-checked in a Lagrange-mesh method for $B=1$ a.u. and in a perturbation theory at small $B$ and $P$. The constructed trial function has the property of being a uniform approximation of the exact eigenfunction. For a Hydrogen atom and a Positronium a double perturbation theory in $B$ and $P$ is developed and the first corrections are found algebraically. A phenomenon of a sharp change of energy behavior for a certain center-of-mass momentum and a fixed magnetic field is indicated.

M. A. Escobar-Ruiz; A. V. Turbiner

2014-07-10T23:59:59.000Z

339

Effect of internal electric field on InAs/GaAs quantum dot solar cells  

SciTech Connect (OSTI)

We studied time-resolved carrier recombination in InAs/GaAs quantum dot (QD) solar cells. The electric field in a p-i-n diode structure spatially separates photoexcited carriers in QDs, strongly affecting the conversion efficiency of intermediate-band solar cells. The radiative decay lifetime is dramatically reduced in a strong electric field (193?kV/cm) by efficient recombination due to strong carrier localization in each QD and significant tunneling-assisted electron escape. Conversely, an electric field of the order of 10?kV/cm maintains electronic coupling in the stacked QDs and diminishes tunneling-assisted electron escape.

Kasamatsu, Naofumi; Kada, Tomoyuki; Hasegawa, Aiko; Harada, Yukihiro; Kita, Takashi [Department of Electrical and Electronic Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai, Nada, Kobe 657-8501 (Japan)

2014-02-28T23:59:59.000Z

340

Surface Tension of Electrolyte Interfaces: Ionic Specificity within a Field-Theory Approach  

E-Print Network [OSTI]

Surface Tension of Electrolyte Interfaces: Ionic Specificity within a Field-Theory Approach Tomer, 1000 Ljubljana, Slovenia (Dated: November 19, 2014) We study the surface tension of ionic solutions expansion beyond the mean-field result. We calculate the excess surface tension and obtain analytical

Andelman, David

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


341

DC response of hot carriers under circularly polarized intense microwave fields and intense magnetic fields in quantum wells  

SciTech Connect (OSTI)

Hot carrier dynamics under intense microwave and crossed magnetic fields are investigated theoretically for the case that the dominant scattering process is inelastic collision, especially intersubband and intrasubband transition in Quantum wells. If the applied electric fields are circularly polarized, the equation of motion forms symmetric on the x-y plane. But the carrier motions are complicated to accumulate because of acceleration and emission process. This situation makes possible to create a variation of the carrier motion, typically the carrier bunching is occurred. This state is a sort of population inversion. The DC response of this system attains strongly negative at appropriate field conditions. Through the simulation for the real case described below, it may include a type of induced emission.

Ishida, Norihisa, E-mail: ishida-norihisa@hotmail.com [Japan Electronics College, 1-25-5 Hyakunin-cho, Shinjuku-ku, Tokyo 169-8522 (Japan)

2013-12-04T23:59:59.000Z

342

Magnetic-field-tuned quantum criticality of the heavy-fermion system YbPtBi  

SciTech Connect (OSTI)

In this paper, we present systematic measurements of the temperature and magnetic field dependencies of the thermodynamic and transport properties of the Yb-based heavy fermion YbPtBi for temperatures down to 0.02 K with magnetic fields up to 140 kOe to address the possible existence of a field-tuned quantum critical point. Measurements of magnetic-field- and temperature-dependent resistivity, specific heat, thermal expansion, Hall effect, and thermoelectric power indicate that the AFM order can be suppressed by an applied magnetic field of Hc?4 kOe. In the H-T phase diagram of YbPtBi, three regimes of its low-temperature states emerge: (I) AFM state, characterized by a spin density wave-like feature, which can be suppressed to T=0 by the relatively small magnetic field of Hc?4 kOe; (II) field-induced anomalous state in which the electrical resistivity follows ??(T)?T1.5 between Hc and ?8 kOe; and (III) Fermi liquid (FL) state in which ??(T)?T2 for H?8 kOe. Regions I and II are separated at T=0 by what appears to be a quantum critical point. Whereas region III appears to be a FL associated with the hybridized 4f states of Yb, region II may be a manifestation of a spin liquid state.

Mun, E. D. [Ames Laboratory; Budko, Serguei L. [Ames Laboratory; Martin, Catalin [Ames Laboratory; Kim, Hyong June [Ames Laboratory; Tanatar, Makariy A. [Ames Laboratory; Park, J.-H. [Florida State University; Murphy, T. [Florida State University; Schmiedeshoff, G. M. [Occidental College; Dilley, N. [Quantum Design; Prozorov, Ruslan [Ames Laboratory; Canfield, Paul C. [Ames Laboratory

2013-02-15T23:59:59.000Z

343

Cosmic density and velocity fields in Lagrangian perturbation theory  

E-Print Network [OSTI]

A first- and second-order relation between cosmic density and peculiar-velocity fields is presented. The calculation is purely Lagrangian and it is derived using the second-order solutions of the Lagrange-Newton system obtained by Buchert & Ehlers. The procedure is applied to two particular solutions given generic initial conditions. In this approach, the continuity equation yields a relation between the over-density and peculiar-velocity fields that automatically satisfies Euler's equation because the orbits are derived from the Lagrange-Newton system. This scheme generalizes some results obtained by Nusser et al. (1991) in the context of the Zel'dovich approximation. As opposed to several other reconstruction schemes, in this approach it is not necessary to truncate the expansion of the Jacobian given by the continuity equation in order to calculate a first- or second-order expression for the density field. In these previous schemes, the density contrast given by (a) the continuity equation and (b) Euler's equation are mutually incompatible. This inconsistency arises as a consequence of an improper handling of Lagrangian and Eulerian coordinates in the analysis. Here, we take into account the fact that an exact calculation of the density is feasible in the Lagrangian picture and therefore an accurate and consistent description is obtained.

Mikel Susperregi; Thomas Buchert

1997-08-04T23:59:59.000Z

344

Quantum ferroelectrics of mixed crystals  

Science Journals Connector (OSTI)

The inverse dielectric susceptibility for quantum ferroelectrics in mixed crystals is computed. As in the perfect crystals we find a logarithmic correction to the quantum mean-field theory. For mixed crystals the correction increases faster in the vicinity of the critical point.

D. Schmeltzer

1984-03-01T23:59:59.000Z

345

Stable and unstable dynamics of Overhauser fields in a double quantum dot  

Science Journals Connector (OSTI)

Nonlinear dynamics of nuclear spin ensembles driven by a two-electron system in a double quantum dot in the Pauli spin blockade (SB) regime is studied experimentally in conjunction with numerical simulation. Dynamic nuclear spin polarization (DNP) is systematically studied by evaluating the current level and its fluctuations. We interpret large current noise in the SB regime as stable feedback noise, where identical Overhauser fields of the two dots are preferred. In contrast, stepwise increases of current in the shallow Coulomb blockade region can be understood as unstable dynamics with significant imbalance of the Overhauser fields, which cancels the external magnetic field in one of the two dots. There, an extremely small transverse Overhauser field can easily lift the SB transport, giving the highest current level, when longitudinal components cancel the applied field.

Sonia Sharmin; Koji Muraki; Toshimasa Fujisawa

2014-03-21T23:59:59.000Z

346

Complete quantization of a diffeomorphism invariant field theory  

E-Print Network [OSTI]

In order to test the canonical quantization programme for general relativity we introduce a reduced model for a real sector of complexified Ashtekar gravity which captures important properties of the full theory. While it does not correspond to a subset of Einstein's gravity it has the advantage that the programme of canonical quantization can be carried out completely and explicitly, both, via the reduced phase space approach or along the lines of the algebraic quantization programme. This model stands in close correspondence to the frequently treated cylindrically symmetric waves. In contrast to other models that have been looked at up to now in terms of the new variables the reduced phase space is infinite dimensional while the scalar constraint is genuinely bilinear in the momenta. The infinite number of Dirac observables can be expressed in compact and explicit form in terms of the original phase space variables. They turn out, as expected, to be non-local and form naturally a set of countable cardinality.

T. Thiemann

1999-10-04T23:59:59.000Z

347

Supersymmetric gauge theories, quantisation of moduli spaces of flat connections, and Liouville theory  

E-Print Network [OSTI]

This is the 11th article in the collection of reviews "Exact results in N=2 supersymmetric gauge theories", ed. J. Teschner. It describes an approach to understanding the 4d/2d relations discovered by Alday, Gaiotto and Tachikawa by establishing a triangle of relations between the zero mode quantum mechanics obtained by localisation of class $\\cal S$ theories, the quantum theory obtained by quantisation of Hitchin moduli spaces, and conformal field theory.

Jrg Teschner

2014-12-22T23:59:59.000Z

348

Supersymmetric gauge theories, quantisation of moduli spaces of flat connections, and Liouville theory  

E-Print Network [OSTI]

This is the 11th article in the collection of reviews "Exact results in N=2 supersymmetric gauge theories", ed. J. Teschner. It describes an approach to understanding the 4d/2d relations discovered by Alday, Gaiotto and Tachikawa by establishing a triangle of relations between the zero mode quantum mechanics obtained by localisation of class $\\cal S$ theories, the quantum theory obtained by quantisation of Hitchin moduli spaces, and conformal field theory.

Teschner, Jrg

2014-01-01T23:59:59.000Z

349

Breakdown of the Equivalence between Energy Content and Weight in a Weak Gravitational Field for a Quantum Body  

E-Print Network [OSTI]

It is shown that weight operator of a composite quantum body in a weak external gravitational field in the post-Newtonian approximation of the General Relativity does not commute with its energy operator, taken in the absence of the field. Nevertheless, the weak equivalence between the expectations values of weight and energy is shown to survive at a macroscopic level for stationary quantum states for the simplest composite quantum body - a hydrogen atom. Breakdown of the weak equivalence between weight and energy at a microscopic level for stationary quantum states can be experimentally detected by studying unusual electromagnetic radiation, emitted by the atoms, supported and moved in the Earth gravitational field with constant velocity, using spacecraft or satellite. For superpositions of stationary quantum states, a breakdown of the above mentioned equivalence at a macroscopic level leads to time dependent oscillations of the expectation values of weight, where the equivalence restores after averaging over time procedure.

Andrei Lebed

2012-05-14T23:59:59.000Z

350

Direct Observation of Optically Forbidden Energy Transfer between CuCl Quantum Cubes via Near-Field Optical Spectroscopy  

Science Journals Connector (OSTI)

We report, for the first time, evidence of near-field energy transfer among CuCl quantum cubes using an ultrahigh-resolution near-field optical microscopy and spectroscopy in the near UV region at 15 K. The sample was high-density CuCl quantum cubes embedded in a NaCl matrix. Measured spatial distributions of the luminescence intensities from 4.6-nm and 6.3-nm quantum cubes clearly established anticorrelation features. This is thought to be a manifestation of the energy transfer from the lowest state of exciton in 4.6-nm quantum cubes to the first dipole-forbidden excited state of exciton in 6.3-nm quantum cubes, which is attributed to the resonant optical near-field interaction.

Tadashi Kawazoe; Kiyoshi Kobayashi; Jungshik Lim; Yoshihito Narita; Motoichi Ohtsu

2002-01-25T23:59:59.000Z

351

The Hamilton-Pontryagin Principle and Multi-Dirac Structures for Classical Field Theories  

E-Print Network [OSTI]

We introduce a variational principle for field theories, referred to as the Hamilton-Pontryagin principle, and we show that the resulting field equations are the Euler-Lagrange equations in implicit form. Secondly, we introduce multi-Dirac structures as a graded analog of standard Dirac structures, and we show that the graph of a multisymplectic form determines a multi-Dirac structure. We then discuss the role of multi-Dirac structures in field theory by showing that the implicit Euler-Lagrange equations for fields obtained from the Hamilton-Pontryagin principle can be described intrinsically using multi-Dirac structures. Lastly, we show a number of illustrative examples, including time-dependent mechanics, nonlinear scalar fields, Maxwell's equations, and elastostatics.

Joris Vankerschaver; Hiroaki Yoshimura; Melvin Leok

2012-07-12T23:59:59.000Z

352

Avalanche shape and exponents beyond mean-field theory  

E-Print Network [OSTI]

Elastic systems, such as magnetic domain walls, density waves, contact lines, and cracks, are all pinned by substrate disorder. When driven, they move via successive jumps called avalanches, with power law distributions of size, duration and velocity. Their exponents, and the shape of an avalanche, defined as its mean velocity as function of time, have recently been studied. They are known approximatively from experiments and simulations, and were predicted from mean-field models, such as the Brownian force model (BFM), where each point of the elastic interface sees a force field which itself is a random walk. As we showed in EPL 97 (2012) 46004, the BFM is the starting point for an $\\epsilon = d_{\\rm c}-d$ expansion around the upper critical dimension, with $d_{\\rm c}=4$ for short-ranged elasticity, and $d_{\\rm c}=2$ for long-ranged elasticity. Here we calculate analytically the ${\\cal O}(\\epsilon)$, i.e. 1-loop, correction to the avalanche shape at fixed duration $T$, for both types of elasticity. The exact expression is well approximated by $\\left_T\\simeq [ Tx(1-x)]^{\\gamma-1} \\exp\\left( {\\cal A}\\left[\\frac12-x\\right]\\right)$, $0

Alexander Dobrinevski; Pierre Le Doussal; Kay Jrg Wiese

2014-07-28T23:59:59.000Z

353

Ab Initio Geometry and Bright Excitation of Carotenoids: Quantum Monte Carlo and Many Body Green's Function Theory Calculations  

E-Print Network [OSTI]

Ab Initio Geometry and Bright Excitation of Carotenoids: Quantum Monte Carlo and Many Body Green state. Many Body Green's Function Theory (MBGFT) calculations of the vertical excitation energy and coupling with Qy of the chlorophyll.8-13 Measurements in several solvents have been reported

Guidoni, Leonardo

354

Quantum dissipative dynamics of adsorbates near metal surfaces: A surrogate Hamiltonian theory applied to hydrogen on nickel  

E-Print Network [OSTI]

Quantum dissipative dynamics of adsorbates near metal surfaces: A surrogate Hamiltonian theory; accepted 18 February 1997 Dissipative dynamics of an adsorbate near a metal surface is formulated of molecules adsorbed on metal surfaces are complicated due to the simultaneous encounter with dis- sipative

Baer, Roi

355

Atomic and Molecular Quantum Theory Course Number: C561 23 The Born-Oppenheimer approximation, the Many Electron  

E-Print Network [OSTI]

Atomic and Molecular Quantum Theory Course Number: C561 23 The Born-Oppenheimer approximation are required. One powerful approximation is called the Born-Oppenheimer approximation. (It does have some limitations and we will discuss these as well.) The Born-Oppenheimer approximation assumes that the nuclei

Iyengar, Srinivasan S.

356

Restricted three-body problem in effective-field-theory models of gravity  

E-Print Network [OSTI]

One of the outstanding problems of classical celestial mechanics was the restricted 3-body prob- lem, in which a planetoid of small mass is subject to the Newtonian attraction of two celestial bodies of large mass, as it occurs, for example, in the sun-earth-moon system. On the other hand, over the last decades, a systematic investigation of quantum corrections to the Newtonian potential has been carried out in the literature on quantum gravity. The present paper studies the effect of these tiny quantum corrections on the evaluation of equilibrium points. It is shown that, despite the extreme smallness of the corrections, there exists no choice of sign of these corrections for which all qualitative features of the restricted 3-body problem in Newtonian theory remain unaffected. Moreover, first-order stability of equilibrium points is characterized by solving a pair of algebraic equations of fifth degree, where some coefficients depend on the Planck length. The coordinates of stable equilibrium points are slightly changed with respect to Newtonian theory, because the planetoid is no longer at equal distance from the two bodies of large mass. The effect is conceptually interesting but too small to be observed, at least for the restricted 3-body problems available in the solar system.

Emmanuele Battista; Giampiero Esposito

2014-02-12T23:59:59.000Z

357

hal-00263678,version2-2Apr2008 On group theory for quantum gates  

E-Print Network [OSTI]

of the three pillars: quantum physics, mathematics and computer science. If large-scale quantum computers can of the stabilizer group in terms of maximal normal subgroups [16], sustain the explanation of quantum (de

Paris-Sud XI, Université de

358

Yb-based heavy fermion compounds and field tuned quantum chemistry  

SciTech Connect (OSTI)

The motivation of this dissertation was to advance the study of Yb-based heavy fermion (HF) compounds especially ones related to quantum phase transitions. One of the topics of this work was the investigation of the interaction between the Kondo and crystalline electric field (CEF) energy scales in Yb-based HF systems by means of thermoelectric power (TEP) measurements. In these systems, the Kondo interaction and CEF excitations generally give rise to large anomalies such as maxima in {rho}(T) and as minima in S(T). The TEP data were use to determine the evolution of Kondo and CEF energy scales upon varying transition metals for YbT{sub 2}Zn{sub 20} (T = Fe, Ru, Os, Ir, Rh, and Co) compounds and applying magnetic fields for YbAgGe and YbPtBi. For YbT{sub 2}Zn{sub 20} and YbPtBi, the Kondo and CEF energy scales could not be well separated in S(T), presumably because of small CEF level splittings. A similar effect was observed for the magnetic contribution to the resistivity. For YbAgGe, S(T) has been successfully applied to determine the Kondo and CEF energy scales due to the clear separation between the ground state and thermally excited CEF states. The Kondo temperature, T{sub K}, inferred from the local maximum in S(T), remains finite as magnetic field increases up to 140 kOe. In this dissertation we have examined the heavy quasi-particle behavior, found near the field tuned AFM quantum critical point (QCP), with YbAgGe and YbPtBi. Although the observed nFL behaviors in the vicinity of the QCP are different between YbAgGe and YbPtBi, the constructed H-T phase diagram including the two crossovers are similar. For both YbAgGe and YbPtBi, the details of the quantum criticality turn out to be complicated. We expect that YbPtBi will provide an additional example of field tuned quantum criticality, but clearly there are further experimental investigations left and more ideas needed to understand the basic physics of field-induced quantum criticality in Yb-based systems.

Mun, Eundeok

2010-07-23T23:59:59.000Z

359

Entanglement, avoided crossings, and quantum chaos in an Ising model with a tilted magnetic field  

SciTech Connect (OSTI)

We study a one-dimensional Ising model with a magnetic field and show that tilting the field induces a transition to quantum chaos. We explore the stationary states of this Hamiltonian to show the intimate connection between entanglement and avoided crossings. In general, entanglement gets exchanged between the states undergoing an avoided crossing with an overall enhancement of multipartite entanglement at the closest point of approach, simultaneously accompanied by diminishing two-body entanglement as measured by concurrence. We find that both for stationary as well as nonstationary states, nonintegrability leads to a destruction of two-body correlations and distributes entanglement more globally.

Karthik, J.; Sharma, Auditya; Lakshminarayan, Arul [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India)

2007-02-15T23:59:59.000Z

360

Dynamical Generation of Spacetime Signature by Massive Quantum Fields on a Topologically Non-Trivial Background  

E-Print Network [OSTI]

The effective potential for a dynamical Wick field (dynamical signature) induced by the quantum effects of massive fields on a topologically non-trivial $D$ dimensional background is considered. It is shown that when the radius of the compactified dimension is very small compared with $\\Lambda^{1/2}$ (where $\\Lambda$ is a proper-time cutoff), a flat metric with Lorentzian signature is preferred on ${\\bf R}^4 \\times {\\bf S}^1$. When the compactification radius becomes larger a careful analysis of the 1-loop effective potential indicates that a Lorentzian signature is preferred in both $D=6$ and $D=4$ and that these results are relatively stable under metrical perturbations.

Sergei D. Odintsov; August Romeo; Robin W. Tucker

1994-06-22T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


361

Basic canonical brackets in the gauge field theoretic models for the Hodge theory  

E-Print Network [OSTI]

We deduce the canonical brackets for a two (1 + 1)-dimensional (2D) free Abelian 1-form as well as a four (3 + 1)-dimensional (4D) 2-form gauge theory by exploiting the beauty and strength of the continuous symmetries of the Becchi-Rouet-Stora-Tyutin (BRST) invariant Lagrangian densities that respect, in totality, six continuous symmetries. These symmetries entail upon these models to become the field theoretic examples for the Hodge theory. Taken together, these symmetries enforce the existence of exactly the same canonical brackets amongst the creation and annihilation operators that appear in the canonical method of quantization for the normal mode expansion of the basic fields of these theories. In other words, we provide an alternative to the canonical method of quantization for our present gauge field theoretic models for the Hodge theory where the continuous symmetries play a decisive role. We conjecture that our method of quantization would be valid for any arbitrary gauge field theoretic model for the Hodge theory in any arbitrary dimension of spacetime.

S. Gupta; R. Kumar; R. P. Malik

2014-01-12T23:59:59.000Z

362

Antiferromagnet-based nuclear spin model of scalable quantum register with inhomogeneous magnetic field  

E-Print Network [OSTI]

As a nuclear spin model of scalable quantum register, the one-dimensional chain of the magnetic atoms with nuclear spins 1/2 substituting the basic atoms in the plate of nuclear spin free easy-axis 3D antiferromagnet is considered. It is formulated the generalized antiferromagnet Hamiltonian in spin-wave approximation (low temperatures) considering the inhomogeneous external magnetic field, which is directed along the easy axis normally to plane of the plate and has a constant gradient along the nuclear spin chain. Assuming a weak gradient, the asymptotic expression for coefficients of unitary transformations to the diagonal form of antiferromagnet Hamiltonian is found. With this result the expression for indirect interspin coupling, which is due to hyperfine nuclear electron coupling in atoms and the virtual spin wave propagation in antiferromagnet ground state, was evaluated. It is shown that the inhomogeneous magnetic field essentially modifies the characteristics of indirect interspin coupling. The indirect interaction essentially grows and even oscillates in relation to the interspin distance when the local field value in the middle point of two considered nuclear spin is close to the critical field for quantum phase transition of spin-flop type in bulk antiferromagnet or close to antiferromagnetic resonance. Thus, the external magnetic field, its gradient, microwave frequency and power can play the role of control parameters for qubit states. Finally, the one and two qubit states decoherence and longitudinal relaxation rate are caused by the interaction of nuclear spins with virtual spin waves in antiferromagnet ground state are calculated.

A. A. Kokin; V. A. Kokin

2008-12-01T23:59:59.000Z

363

Determination of the 85 Rb ng-series quantum defect by electric-field-induced resonant energy  

E-Print Network [OSTI]

Determination of the 85 Rb ng-series quantum defect by electric-field-induced resonant energy of an electric field 1 . The resonant energy transfer process between Rydberg atoms is driven by the electric-series of potassium. The range of electric fields or "width" over which signifi- cant resonant energy transfer can

Le Roy, Robert J.

364

Weakly interacting two-dimensional system of dipoles: Limitations of the mean-field theory  

Science Journals Connector (OSTI)

We consider a homogeneous two-dimensional Bose gas with repulsive dipole-dipole interactions. The ground-state equation of state, calculated using the diffusion Monte Carlo method, shows quantitative differences from the predictions of the commonly used Gross-Pitaevskii mean-field theory. The static structure factor, pair distribution function, and condensate fraction are calculated in a wide range of the gas parameter. Differences from mean-field theory are reflected in the frequency of the lowest breathing mode for harmonically trapped systems.

G. E. Astrakharchik, J. Boronat, J. Casulleras, I. L. Kurbakov, and Yu. E. Lozovik

2007-06-29T23:59:59.000Z

365

Engineering of Quantum Hall Effect from Type IIA String Theory on The K3 Surface  

E-Print Network [OSTI]

Using D-brane configurations on the K3 surface, we give six dimensional type IIA stringy realizations of the Quantum Hall Effect (QHE) in 1+2 dimensions. Based on the vertical and horizontal lines of the K3 Hodge diamond, we engineer two different stringy realizations. The vertical line presents a realization in terms of D2 and D6-branes wrapping the K3 surface. The horizontal one is associated with hierarchical stringy descriptions obtained from a quiver gauge theory living on a stack of D4-branes wrapping intersecting 2-spheres embedded in the K3 surface with deformed singularities. These geometries are classified by three kinds of the Kac-Moody algebras: ordinary, i.e finite dimensional, affine and indefinite. We find that no stringy QHE in 1+2 dimensions can occur in the quiver gauge theory living on intersecting 2-spheres arranged as affine Dynkin diagrams. Stringy realizations of QHE can be done only for the finite and indefinite geometries. In particular, the finite Lie algebras give models with fractional filling fractions, while the indefinite ones classify models with negative filling fractions which can be associated with the physics of holes in the graphene.

Adil Belhaj; Antonio Segui

2010-07-02T23:59:59.000Z

366

A conformal field theory description of magnetic flux fractionalization in Josephson junction ladders  

E-Print Network [OSTI]

We show how the recently proposed effective theory for a Quantum Hall system at "paired states" filling v=1 (Mod. Phys. Lett. A 15 (2000) 1679; Nucl. Phys. B641 (2002) 547), the twisted model (TM), well adapts to describe the phenomenology of Josephson Junction ladders (JJL) in the presence of defects. In particular it is shown how naturally the phenomenon of flux fractionalization takes place in such a description and its relation with the discrete symmetries present in the TM. Furthermore we focus on closed geometries, which enable us to analyze the topological properties of the ground state of the system in relation to the presence of half flux quanta.

G. Cristofano; V. Marotta; A. Naddeo; G. Niccoli

2005-09-30T23:59:59.000Z

367

Measuring CP violation within Effective Field Theory of inflation from CMB  

E-Print Network [OSTI]

In this work we propose an Effective Field Theory of inflation taking into account the spin density of matter which contributes to torsion. We first explicitly show that torsion mimics the role of a scalar field which controls the dynamics of inflation. We have obtained a strict bound on the CP violating $\\theta$ parameter, ${\\cal O}(10^{-10})<\\theta<{\\cal O}(10^{-9})$, using Planck+WMAP9 best fit cosmological parameters.

Sayantan Choudhury; Barun Kumar Pal; Banasri Basu; Pratul Bandyopadhyay

2014-09-21T23:59:59.000Z

368

Exotic Low Density Fermion States in the Two Measures Field Theory: Neutrino Dark Energy  

E-Print Network [OSTI]

We study a new field theory effect in the cosmological context in the Two Measures Field Theory (TMT). TMT is an alternative gravity and matter field theory where the gravitational interaction of fermionic matter is reduced to that of General Relativity when the energy density of the fermion matter is much larger than the dark energy density. In this case also the 5-th force problem is solved automatically. In the opposite limit, where the magnitudes of fermionic energy density and scalar field dark energy density become comparable, nonrelativistic fermions can participate in the cosmological expansion in a very unusual manner. Some of the features of such states in a toy model of the late time universe filled with homogeneous scalar field and uniformly distributed nonrelativistic neutrinos: neutrino mass increases as m ~ a^{3/2}; the neutrino gas equation-of-state approaches w=-1, i.e. neutrinos behave as a sort of dark energy; the total (scalar field + neutrino) equation-of-state also approaches w=-1; the t...

Guendelman, E I

2006-01-01T23:59:59.000Z

369

Analysis of the equations of mathematical physics and foundations of field theories with the help of skew-symmetric differential forms  

E-Print Network [OSTI]

In the paper it is shown that, even without a knowledge of the concrete form of the equations of mathematical physics and field theories, with the help of skew-symmetric differential forms one can see specific features of the equations of mathematical physics, the relation between mathematical physics and field theory, to understand the mechanism of evolutionary processes that develop in material media and lead to emergency of physical structures forming physical fields. This discloses a physical meaning of such concepts like "conservation laws", "postulates" and "causality" and gives answers to many principal questions of mathematical physics and general field theory. In present paper, beside the exterior forms, the skew-symmetric differential forms, whose basis (in contrast to the exterior forms) are deforming manifolds, are used. Mathematical apparatus of such differential forms(which were named evolutionary ones) includes nontraditional elements like nonidentical relations and degenerate transformations and this enables one to describe discrete transitions, quantum steps, evolutionary processes, and generation of various structures.

L. I. Petrova

2005-12-21T23:59:59.000Z

370

The $\\gamma N\\to \\De$ transition in chiral effective-field theory  

SciTech Connect (OSTI)

We describe the pion electroproduction processes in the {Delta}(1232)-resonance region within the framework of chiral effective-field theory. By studying the observables of pion electroproduction in a next-to-leading order calculation we are able to make predictions and draw conclusions on the properties of the N {yields} {Delta} electromagnetic form factors.

Vladimir Pascalutsa; Marc Vanderhaeghen

2006-04-27T23:59:59.000Z

371

The gamma N ---> Delta transition in chiral effective-field theory.  

SciTech Connect (OSTI)

We describe the pion electroproduction processes in the {Delta}(1232)-resonance region within the framework of chiral effective-field theory. By studying the observables of pion electroproduction in a next-to-leading order calculation we are able to make predictions and draw conclusions on the properties of the N {yields} {Delta} electromagnetic form factors.

Vladimir Pascalutsa; Marc Vanderhaeghen

2006-04-27T23:59:59.000Z

372

Muon g -2 from and e+ a simple exercise in effective field theory  

E-Print Network [OSTI]

Muon g - 2 from and e+ e- data ­ a simple exercise in effective field theory ­ Fred Jegerlehner HU function discrepancy. Consequences for the muon g - 2 are discussed. F. Jegerlehner CALC 2012, JINR Dubna, July 29, 2012 #12;Outline of Talk: O Prelude: The hadronic vacuum polarization contribution to the muon

Röder, Beate

373

Basic canonical brackets in the gauge field theoretic models for the Hodge theory  

E-Print Network [OSTI]

We deduce the canonical brackets for a two (1 + 1)-dimensional (2D) free Abelian 1-form as well as a four (3 + 1)-dimensional (4D) 2-form gauge theory by exploiting the beauty and strength of the continuous symmetries of the Becchi-Rouet-Stora-Tyutin (BRST) invariant Lagrangian densities that respect, in totality, six continuous symmetries. These symmetries entail upon these models to become the field theoretic examples for the Hodge theory. Taken together, these symmetries enforce the existence of exactly the same canonical brackets amongst the creation and annihilation operators that appear in the canonical method of quantization for the normal mode expansion of the basic fields of these theories. In other words, we provide an alternative to the canonical method of quantization for our present gauge field theoretic models for the Hodge theory where the continuous symmetries play a decisive role. We conjecture that our method of quantization would be valid for any arbitrary gauge field theoretic model for th...

Gupta, S; Malik, R P

2014-01-01T23:59:59.000Z

374

Perturbative Ward identities for Yang-Mills field theory stochastically quantized  

Science Journals Connector (OSTI)

We compute the divergent part of the three-point vertex function of the non-Abelian Yang-Mills gauge field theory within the stochastic quantization approach to the one-loop order. This calculation allows us to find four renormalization constants which, together with the four previously obtained, verify, to the calculated order, some Ward identities.

A. Muoz Sudupe

1986-04-15T23:59:59.000Z

375

Oceanic Internal-Wave Field: Theory of Scale-Invariant Spectra YURI V. LVOV  

E-Print Network [OSTI]

of a nearly universal internal-wave energy spectrum in the ocean, first described by Garrett and Munk (Garrett framework that allows a detailed analysis of power-law spectra of internal waves in the ocean. WeOceanic Internal-Wave Field: Theory of Scale-Invariant Spectra YURI V. LVOV Rensselaer Polytechnic

Tabak, Esteban G.

376

Real-time quantum trajectories for classically allowed dynamics in strong laser fields  

E-Print Network [OSTI]

Both the physical picture of the dynamics of atoms and molecules in intense infrared fields and its theoretical description use the concept of electron trajectories. Here we address a key question which arises in this context: Are distinctly quantum features of these trajectories, such as the complex-valued coordinates, physically relevant in the classically allowed region of phase space, and what is their origin? First, we argue that solutions of classical equations of motion can account for quantum effects. To this end, we construct an exact solution to the classical Hamilton-Jacobi equation which accounts for dynamics of the wave packet, and show that this solution is physically correct in the limit $\\hbar \\to 0$. Second, we show that imaginary components of classical trajectories are directly linked to the finite size of the initial wavepacket in momentum space. This way, if the electronic wavepacket produced by optical tunneling in strong infrared fiels is localised both in coordinate and momentum, its m...

Plimak, L I

2015-01-01T23:59:59.000Z

377

Theory of substrate, Zeeman, and electron-phonon interaction effects on the quantum capacitance in graphene  

SciTech Connect (OSTI)

Since the discovery of graphene, a lot of interest has been attracted by the zeroth Landau level, which has no analog in the conventional two dimensional electron gas. Recently, lifting of the spin and valley degeneracies has been confirmed experimentally by capacitance measurements, while in transport experiments, this is difficult due to the scattering in the device. In this context, we model interaction effects on the quantum capacitance of graphene in the presence of a perpendicular magnetic field, finding good agreement with experiments. We demonstrate that the valley degeneracy is lifted by the substrate and by Kekule distortion, whereas the spin degeneracy is lifted by Zeeman interaction. The two cases can be distinguished by capacitance measurements.

Tahir, M. [PSE Division, KAUST, Thuwal 23955-6900 (Saudi Arabia); Department of Physics, University of Sargodha, Sargodha 40100 (Pakistan); Sabeeh, K. [Department of Physics, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Shaukat, A. [Department of Physics, University of Sargodha, Sargodha 40100 (Pakistan); Schwingenschlgl, U., E-mail: Udo.Schwingenschlogl@kaust.edu.sa [PSE Division, KAUST, Thuwal 23955-6900 (Saudi Arabia)

2013-12-14T23:59:59.000Z

378

Chiral symmetry and effective field theories for hadronic, nuclear and stellar matter  

E-Print Network [OSTI]

Chiral symmetry, first entering in nuclear physics in the 1970's for which Gerry Brown played a seminal role, has led to a stunningly successful framework for describing strongly-correlated nuclear dynamics both in finite and infinite systems. We review how the early germinal idea, conceived with the soft-pion theorems in the pre-QCD era, has evolved into a highly predictive theoretical framework for nuclear physics, aptly assessed by Steven Weinberg: "it (chiral effective field theory) allows one to show in a fairly convincing way that what they (nuclear physicists) have been doing all along... is the correct first step in a consistent approximation scheme." Our review recounts both how the theory presently fares in confronting Nature and how one can understand its extremely intricate workings in terms of the multifaceted aspects of chiral symmetry, namely, chiral perturbation theory, skyrmions, Landau Fermi-liquid theory, the Cheshire cat phenomenon, and hidden local and mended symmetries.

Jeremy W. Holt; Mannque Rho; Wolfram Weise

2014-11-24T23:59:59.000Z

379

Chiral symmetry and effective field theories for hadronic, nuclear and stellar matter  

E-Print Network [OSTI]

Chiral symmetry, first entering in nuclear physics in the 1970's for which Gerry Brown played a seminal role, has led to a stunningly successful framework for describing strongly-correlated nuclear dynamics both in finite and infinite systems. We review how the early germinal idea, conceived with the soft-pion theorems in the pre-QCD era, has evolved into a highly predictive theoretical framework for nuclear physics, aptly assessed by Steven Weinberg: "it (chiral effective field theory) allows one to show in a fairly convincing way that what they (nuclear physicists) have been doing all along... is the correct first step in a consistent approximation scheme." Our review recounts both how the theory presently fares in confronting Nature and how one can understand its extremely intricate workings in terms of the multifaceted aspects of chiral symmetry, namely, chiral perturbation theory, skyrmions, Landau Fermi-liquid theory, the Cheshire cat phenomenon, and hidden local and mended symmetries.

Holt, Jeremy W; Weise, Wolfram

2014-01-01T23:59:59.000Z

380

Magnetic field control of the intraband optical absorption in two-dimensional quantum rings  

SciTech Connect (OSTI)

Linear and nonlinear optical absorption coefficients of the two-dimensional semiconductor ring in the perpendicular magnetic field B are calculated within independent electron approximation. Characteristic feature of the energy spectrum are crossings of the levels with adjacent nonpositive magnetic quantum numbers as the intensity B changes. It is shown that the absorption coefficient of the associated optical transition is drastically decreased at the fields corresponding to the crossing. Proposed model of the Volcano disc allows to get simple mathematical analytical results, which provide clear physical interpretation. An interplay between positive linear and intensity-dependent negative cubic absorption coefficients is discussed; in particular, critical light intensity at which additional resonances appear in the total absorption dependence on the light frequency is calculated as a function of the magnetic field and levels' broadening.

Olendski, O., E-mail: oolendski@ksu.edu.sa [King Abdullah Institute for Nanotechnology, King Saud University, P.O. Box 2454, Riyadh 11451 (Saudi Arabia); Barakat, T., E-mail: tbarakat@ksu.edu.sa [Department of Physics, King Saud University, P.O. Box 2454, Riyadh 11451 (Saudi Arabia)

2014-02-28T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


381

Hypercomplex Algebras and their application to the mathematical formulation of Quantum Theory  

E-Print Network [OSTI]

Quantum theory (QT), namely in terms of Schr\\"odinger's 1926 wave functions in general requires complex numbers to be formulated. However, it soon turned out to even require some hypercomplex algebra. Incorporating Special Relativity leads to an equation (Dirac 1928) requiring pairwise anti-commuting coefficients, usually $4\\times 4$ matrices. A unitary ring of square matrices is an associative hypercomplex algebra by definition. Since only the algebraic properties and relations of the elements matter, we replace the matrices by biquaternions. In this paper, we first consider the basics of non-relativistic and relativistic QT. Then we introduce general hypercomplex algebras and also show how a relativistic quantum equation like Dirac's one can be formulated using biquaternions. Subsequently, some algebraic preconditions for operations within hypercomplex algebras and their subalgebras will be examined. For our purpose equations akin to Schr\\"odinger's should be able to be set up and solved. Functions of complementary variables should be Fourier transforms of each other. This should hold within a purely non-real subspace which must hence be a subalgebra. Furthermore, it is an ideal denoted by $\\mathcal{J}$. It must be isomorphic to $\\mathbb{C}$, hence containing an internal identity element. The bicomplex numbers will turn out to fulfil these preconditions, and therefore, the formalism of QT can be developed within its subalgebras. We also show that bicomplex numbers encourage the definition of several different kinds of conjugates. One of these treats the elements of $\\mathcal{J}$ like the usual conjugate treats complex numbers. This defines a quantity what we call a modulus which, in contrast to the complex absolute square, remains non-real (but may be called `pseudo-real'). However, we do not conduct an explicit physical interpretation here but we leave this to future examinations.

Torsten Hertig; Jens Philip Hhmann; Ralf Otte

2014-06-04T23:59:59.000Z

382

Constructing a class of solutions for the Hamilton-Jacobi equation in field theory  

SciTech Connect (OSTI)

A new approach leading to the formulation of the Hamilton-Jacobi equation for field theories is investigated within the framework of jet bundles and multisymplectic manifolds. An algorithm associating classes of solutions to given sets of boundary conditions of the field equations is provided. The paper also puts into evidence the intrinsic limits of the Hamilton-Jacobi method as an algorithm to determine families of solutions of the field equations, showing how the choice of the boundary data is often limited by compatibility conditions.

Bruno, Danilo [Dipartimento di Matematica, Universita di Genova, Via Dodecaneso, 35-16146 Genova (Italy)

2007-11-15T23:59:59.000Z

383

Modern applications of covariant density functional theory  

E-Print Network [OSTI]

Modern applications of Covariant Density Functional Theory (CDFT) are discussed. First we show a systematic investigation of fission barriers in actinide nuclei within constraint relativistic mean field theory allowing for triaxial deformations. In the second part we discuss a microscopic theory of quantum phase transitions (QPT) based on the relativistic generator coordinate method.

P. Ring; H. Abusara; A. V. Afanasjev; G. A. Lalazissis; T. Niksic; D. Vretenar

2011-09-19T23:59:59.000Z

384

Quantum Chromodynamics and nuclear physics at extreme energy density. Progress report, May 1992--April 1993  

SciTech Connect (OSTI)

This report discusses research in the following topics: Hadron structure physics; relativistic heavy ion collisions; finite- temperature QCD; real-time lattice gauge theory; and studies in quantum field theory.

Mueller, B.

1993-05-15T23:59:59.000Z

385

Infrared near-field spectroscopy of trace explosives using an external cavity quantum cascade laser  

SciTech Connect (OSTI)

Utilizing a broadly-tunable external cavity quantum cascade laser for scattering-type scanning near-field optical microscopy (s-SNOM), we measure infrared spectra of explosives particles by probing characteristic nitro-group resonances in the 7.1-7.9 m wavelength range. Measurements are presented with spectral resolution of 0.25 cm-1, spatial resolution of 25 nm, <100 attomolar sensitivity, and at a rapid acquisition time of 90 s per spectrum. We demonstrate high reproducibility of the acquired s-SNOM spectra with very high signal-to-noise ratios and relative noise of <0.02 in self-homodyne detection.

Craig, Ian M.; Taubman, Matthew S.; Lea, Alan S.; Phillips, Mark C.; Josberger, Erik E.; Raschke, Markus Bernd

2013-12-16T23:59:59.000Z

386

Bright-to-dark exciton transition in symmetric coupled quantum wells induced by an in-plane magnetic field  

Science Journals Connector (OSTI)

The energy dispersion of an exciton in a coupled quantum well is modified by an external in-plane magnetic field. We find that the in-plane magnetic field can shift the ground state of the magnetoexciton from a zero in-plane center-of-mass (CM) momentum to a finite CM momentum, and render the ground state of the magnetoexciton stable against radiative recombination due to momentum conservation. At the same time, a spatial separation of the electron and hole is realized. Thus an in-plane magnetic field can be used to tailor the radiative properties of excitons in coupled quantum wells.

Kai Chang and F. M. Peeters

2001-03-28T23:59:59.000Z

387

Role of exchange in density-functional theory for weakly interacting systems: Quantum Monte Carlo analysis of electron density and interaction energy  

E-Print Network [OSTI]

We analyze the density-functional theory (DFT) description of weak interactions by employing diffusion and reptation quantum Monte Carlo (QMC) calculations, for a set of benzene-molecule complexes. While the binding energies ...

Grossman, Jeffrey C.

388

Field-theory calculation of the electric dipole moment of the neutron and paramagnetic atoms  

E-Print Network [OSTI]

Electric dipole moments (edms) of bound states that arise from the constituents having edms are studied with field-theoretic techniques. The systems treated are the neutron and a set of paramagnetic atoms. In the latter case it is well known that the atomic edm differs greatly from the electron edm when the internal electric fields of the atom are taken into account. In the nonrelativistic limit these fields lead to a complete suppression, but for heavy atoms large enhancement factors are present. A general bound-state field theory approach applicable to both the neutron and paramagnetic atoms is set up. It is applied first to the neutron, treating the quarks as moving freely in a confining spherical well. It is shown that the effect of internal electric fields is small in this case. The atomic problem is then revisited using field-theory techniques in place of the usual Hamiltonian methods, and the atomic enhancement factor is shown to be consistent with previous calculations. Possible application of bound-state techniques to other sources of the neutron edm is discussed.

S. A. Blundell; J. Griffith; J. Sapirstein

2012-05-10T23:59:59.000Z

389

The Quantum Vacuum and the Cosmological Constant Problem  

E-Print Network [OSTI]

The cosmological constant problem arises at the intersection between general relativity and quantum field theory, and is regarded as a fundamental problem in modern physics. In this paper we describe the historical and conceptual origin of the cosmological constant problem which is intimately connected to the vacuum concept in quantum field theory. We critically discuss how the problem rests on the notion of physical real vacuum energy, and which relations between general relativity and quantum field theory are assumed in order to make the problem well-defined.

Svend Erik Rugh; Henrik Zinkernagel

2000-12-28T23:59:59.000Z

390

The Quantum Vacuum and the Cosmological Constant Problem  

E-Print Network [OSTI]

The cosmological constant problem arises at the intersection between general relativity and quantum field theory, and is regarded as a fundamental problem in modern physics. In this paper we describe the historical and conceptual origin of the cosmological constant problem which is intimately connected to the vacuum concept in quantum field theory. We critically discuss how the problem rests on the notion of physical real vacuum energy, and which relations between general relativity and quantum field theory are assumed in order to make the problem well-defined.

Rugh, S E; Rugh, Svend Erik; Zinkernagel, Henrik

2000-01-01T23:59:59.000Z

391

Polarization-entangled photon generation by a semiconductor quantum dot coupled to a cavity interacting with external fields  

E-Print Network [OSTI]

We theoretically investigate polarization-entangled photon generation by using a semiconductor quantum dot embedded in a microcavity. The entangled states can be produced by the application of two cross-circularly polarized laser fields. The quantum dot nanostructure is considered as a four-level system (ground, two excitons and bi-exciton states) and the theoretical study relies on the dressed states scheme. The quantum correlations, reported in terms of the entanglement of formation, are extensively studied for several values of the important parameters of the quantum dot system as the bi-exciton binding energy, {the decoherence times of the characteristic transitions, the quality factor of the cavity} and the intensities of the applied fields.

Kostas Blekos; Nikos Iliopoulos; Maria-Eftaksia Stasinou; Evaggelos Vlachos; Andreas F. Terzis

2014-04-07T23:59:59.000Z

392

Quantum theory, gravity, and the standard model of particle physics : using the hints of today to build the final theory of tomorrow  

E-Print Network [OSTI]

When a mountaineer is ascending one of the great peaks of the Himalayas she knows that an entirely new vista awaits her at the top, whose ramifications will be known only after she gets there. Her immediate goal though, is to tackle the obstacles on the way up, and reach the summit. In a similar vein, one of the immediate goals of contemporary theoretical physics is to build a quantum, unified description of general relativity and the standard model of particle physics. Once that peak has been reached, a new (yet unknown) vista will open up. In this essay I propose a novel approach towards this goal. One must address and resolve a fundamental unsolved problem in the presently known formulation of quantum theory : the unsatisfactory presence of an external classical time in the formulation. Solving this problem takes us to the very edge of theoretical physics as we know it today!

T. P. Singh

2010-01-19T23:59:59.000Z

393

Widely tuneable scattering-type scanning near-field optical microscopy using pulsed quantum cascade lasers  

SciTech Connect (OSTI)

We demonstrate the use of a pulsed quantum cascade laser, wavelength tuneable between 6 and 10??m, with a scattering-type scanning near-field optical microscope (s-SNOM). A simple method for calculating the signal-to-noise ratio (SNR) of the s-SNOM measurement is presented. For pulsed lasers, the SNR is shown to be highly dependent on the degree of synchronization between the laser pulse and the sampling circuitry; in measurements on a gold sample, the SNR is 26 with good synchronization and less than 1 without. Simulations and experimental s-SNOM images, with a resolution of 100?nm, corresponding to ?/80, and an acquisition time of less than 90 s, are presented as proof of concept. They show the change in the field profile of plasmon-resonant broadband antennas when they are excited with wavelengths of 7.9 and 9.5??m.

Yoxall, Edward, E-mail: edward.yoxall@imperial.ac.uk; Rahmani, Mohsen; Maier, Stefan A.; Phillips, Chris C. [The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom)] [The Blackett Laboratory, Department of Physics, Imperial College London, London SW7 2AZ (United Kingdom); Navarro-Ca, Miguel [Optical and Semiconductor Devices Group, Department of Electrical and Electronic Engineering, Imperial College London, London SW7 2BT (United Kingdom)] [Optical and Semiconductor Devices Group, Department of Electrical and Electronic Engineering, Imperial College London, London SW7 2BT (United Kingdom)

2013-11-18T23:59:59.000Z

394

Materials Bound by Non-Chemical Forces: External Fields and the Quantum Vacuum  

E-Print Network [OSTI]

We discuss materials which owe their stability to external fields. These include: 1) external electric or magnetic fields, and 2) quantum vacuum fluctuations in these fields induced by suitable boundary conditions (the Casimir effect). Instances of the first case include the floating water bridge and ferrofluids in magnetic fields. An example of the second case is taken from biology where the Casimir effect provides an explanation of the formation of stacked aggregations or "rouleaux" by negatively charged red blood cells. We show how the interplay between electrical and Casimir forces can be used to drive self-assembly of nano-structured materials, and could be generalized both as a probe of Casimir forces and as a means of manufacturing nanoscale structures. Interestingly, all the cases discussed involve the generation of the somewhat exotic negative pressures. We note that very little is known about the phase diagrams of most materials in the presence of external fields other than those represented by the macroscopic scalar quantities of pressure and temperature. Many new and unusual states of matter may yet be undiscovered.

John Swain; Allan Widom; Yogendra Srivastava

2014-04-29T23:59:59.000Z

395

Theory of ballistic transport through a 3D-1D-3D quantum system  

Science Journals Connector (OSTI)

Ballistic transport through a three-dimensionalone-dimensionalthree-dimensional quantum system has been studied theoretically. Based on an exact quantum-mechanical formulation, the quantization of the conductance in units of 2e2/h of this vertical analog to the split-gate defined quantum channel in a two-dimensional electron gas has been proved. By taking into account the mode degeneracy in the lateral confined quantum pillar, multiple conductance plateaus, i.e., the conductance changes in steps of multiples of 2e2/h, are shown to appear in the quantum system.

Hongqi Xu

1993-09-15T23:59:59.000Z

396

Effect of a magnetic field on the excitonic luminescence line shape in a quantum well  

Science Journals Connector (OSTI)

The effect of magnetic field on the excitonic photoluminescence line shape has been studied in a high-quality single GaAs-AlxGa1-xAs quantum well grown by the molecular-beam-epitaxy technique. An increase of magnetic field from 0 to 6 T has been found to result in (1) a decrease in the Lorentzian contribution ?0 to the line shape from ?0(0 T)=0.5040.01 meV to ?0(6 T)=0.3360.01 meV due to the formation of a quasi-zero-dimensional density of states. This leads, in turn, to an increase in the exciton dephasing time due to the inhibition of the carrier relaxation, and (2) an increase in the Gaussian contribution from ?(0 T)=0.24 meV to ?(6 T)=0.39 meV, attributed to the shrinking of the exciton wave function in real space; the last effect causing the exciton to become more responsive to the statistical potential fluctuations at the quantum-well interfaces.

I. Aksenov; J. Kusano; Y. Aoyagi; T. Sugano; T. Yasuda; Y. Segawa

1995-02-15T23:59:59.000Z

397

5D actions for 6D self-dual tensor field theory  

Science Journals Connector (OSTI)

We present two equivalent five-dimensional actions for six-dimensional (N,0) N=1,2 supersymmetric theories of a self-dual tensor whose one spatial dimension is compactified on a circle. The Kaluza-Klein tower consists of a massless vector and an infinite number of massive self-dual tensor multiplets living in five dimensions. The self-duality follows from the equation of motion. Both actions are quadratic in field variables without any auxiliary field. When lifted back to six dimensions, one of them gives a supersymmetric extension of the bosonic formulation for the chiral two-form tensor by Perry and Schwarz.

Kimyeong Lee and Jeong-Hyuck Park

2001-10-12T23:59:59.000Z

398

Quantum Gravity Phenomenology and Lorentz Violation  

E-Print Network [OSTI]

If quantum gravity violates Lorentz symmetry, the prospects for observational guidance in understanding quantum gravity improve considerably. This article briefly reviews previous work on Lorentz violation (LV) and discusses aspects of the effective field theory framework for parametrizing LV effects. Current observational constraints on LV are then summarized, focusing on effects in QED at order E/M_Planck.

Ted Jacobson; Stefano Liberati; David Mattingly

2004-04-15T23:59:59.000Z

399

Regge Field Theory in zero transverse dimensions: loops versus "net" diagrams  

E-Print Network [OSTI]

Toy models of interacting Pomerons with triple and quaternary Pomeron vertices in zero transverse dimension are investigated. Numerical solutions for eigenvalues and eigenfunctions of the corresponding Hamiltonians are obtained, providing the quantum solution for the scattering amplitude in both models. The equations of motion for the Lagrangians of the theories are also considered and the classical solutions of the equations are found. Full two-point Green functions ("effective" Pomeron propagator) and amplitude of diffractive dissociation process are calculated in the framework of RFT-0 approach. The importance of the loops contribution in the amplitude at different values of the model parameters is discussed as well as the difference between the models with and without quaternary Pomeron vertex.

Sergey Bondarenko

2010-11-22T23:59:59.000Z

400

Spectral Analysis of an Effective Hamiltonian in Nonrelativistic Quantum  

E-Print Network [OSTI]

Department of Mathematics, Hokkaido University Sapporo 060-0810 Japan E-mail: arai with the quantum radiation field (for reviews on recent developments of mathematical theory of nonrelativistic QED with the quantum radiation field. This kind of approach (heuristic) was first given by Welton [14], based

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401

Direct and indirect excitons in semiconductor coupled quantum wells in an applied electric field  

Science Journals Connector (OSTI)

An accurate calculation of the exciton ground and excited states in AlGaAs and InGaAs coupled quantum wells (CQWs) in an external electric field is presented. An efficient and straightforward algorithm of solving the Schrdinger equation in real space has been developed and exciton binding energies, oscillator strengths, lifetimes, and absorption spectra are calculated for applied electric fields up to 100 kV/cm. It is found that in a symmetric 848-nm GaAs/Al0.33Ga0.67As CQW structure, the ground state of the system switches from direct to indirect exciton at approximately 5 kV/cm with dramatic changes of its binding energy and oscillator strength while the bright excited direct-exciton state remains almost unaffected. It is shown that the excitonic lifetime is dominated either by the radiative recombination or by tunneling processes at small/large values of the electric field, respectively. The calculated lifetime of the exciton ground state as a function of the bias voltage is in a quantitative agreement with low-temperature photoluminescence measurements. We have also made freely available a numerical code for calculation of the optical properties of direct and indirect excitons in CQWs in an electric field.

K. Sivalertporn, L. Mouchliadis, A. L. Ivanov, R. Philp, and E. A. Muljarov

2012-01-17T23:59:59.000Z

402

On the 'principle of the quantumness', the quantumness of Relativity, and the computational grand-unification  

SciTech Connect (OSTI)

I will argue that the proposal of establishing operational foundations of Quantum Theory should have top-priority, and that the Lucien Hardy's program on Quantum Gravity should be paralleled by an analogous program on Quantum Field Theory (QFT), which needs to be reformulated, notwithstanding its experimental success. In this paper, after reviewing recently suggested operational 'principles of the quantumness', I address the problem on whether Quantum Theory and Special Relativity are unrelated theories, or instead, if the one implies the other. I show how Special Relativity can be indeed derived from causality of Quantum Theory, within the computational paradigm 'the universe is a huge quantum computer', reformulating QFT as a Quantum-Computational Field Theory (QCFT). In QCFT Special Relativity emerges from the fabric of the computational network, which also naturally embeds gauge invariance. In this scheme even the quantization rule and the Planck constant can in principle be derived as emergent from the underlying causal tapestry of space-time. In this way Quantum Theory remains the only theory operating the huge computer of the universe.Is the computational paradigm only a speculative tautology (theory as simulation of reality), or does it have a scientific value? The answer will come from Occam's razor, depending on the mathematical simplicity of QCFT. Here I will just start scratching the surface of QCFT, analyzing simple field theories, including Dirac's. The number of problems and unmotivated recipes that plague QFT strongly motivates us to undertake the QCFT project, since QCFT makes all such problems manifest, and forces a re-foundation of QFT.

D'Ariano, Giacomo Mauro [QUIT Group, Dipartimento di Fisica 'A. Volta', 27100 Pavia (Italy) and Center for Photonic Communication and Computing, Northwestern University, Evanston, IL 60208 (Italy)

2010-05-04T23:59:59.000Z

403

Magnetotransport theory in quantum dots: 3D-0D and 2D-0D tunneling and angular momentum selection rules  

Science Journals Connector (OSTI)

A study of magnetotransport through quantum dots is presented. The model allows one to analyze tunneling both from bulk-like contacts and from 2D accumulation layers. The fine features in the I-V characteristics due to the quantum dot states are known to be shifted to different voltages depending upon the value of the magnetic field. While this effect is also well reproduced by our calculations, in this work we concentrate on the amplitude of each current resonance as a function of the magnetic field. Such amplitudes show oscillations reflecting the variation of the density of states at the Fermi energy in the emitter. Furthermore the amplitude increases as a function of the magnetic field for certain features while it decreases for others. In particular, we demonstrate that the behavior of the amplitude of the current resonances is linked to the value of the angular momentum of each dot level through which tunneling occurs. We show that a selection rule on the angular momentum must be satisfied. As a consequence, tunneling through specific dot states is strongly suppressed and sometimes prohibited altogether by the presence of the magnetic field. This will allow to extract from the experimental curves detailed information on the nature of the quantum-dot wave functions involved in the electronic transport. Furthermore, when tunneling occurs from a two-dimensional accumulation layer to the quantum dot, the presence of a magnetic field hugely increases the strength of some resonant features. This effect is predicted by our model and, to the best of our knowledge, has never been observed.

B. Jouault; M. Boero; G. Faini; J. C. Inkson

1999-02-15T23:59:59.000Z

404

Nanoindentation and near-field spectroscopy of single semiconductor quantum dots  

Science Journals Connector (OSTI)

Low-temperature near-field scanning optical microscopy was used to study the dependence of the emission spectra of single self-organized InAs on GaAs, InAs on AlAs and InP on GaInP quantum dots (QDs) on contact pressure exerted by a near-field optical fiber tip (nanoindentation). A large energy shift (up to 150 meV), broadening (up to 10 meV), and intensity increase (up to one order of magnitude) of single QD emission lines have been observed at tip compressions up to 70 nm. Ground state energy shift rates from 0.5 to 3.5 meV/nm have been measured for different aperture types (rounded and flat, metal coated and uncoated) and sizes (50300 nm) in agreement with numerical calculations using PicusBir orbital-strain Hamiltonian. A reduction of the hydrostatic pressure coefficient due to a nonuniform In distribution in self-organized QDs has been observed. Anomalously strong lateral inhomogeneity of the local stress field has been observed.

A. M. Mintairov; K. Sun; J. L. Merz; C. Li; A. S. Vlasov; D. A. Vinokurov; O. V. Kovalenkov; V. Tokranov; S. Oktyabrsky

2004-04-05T23:59:59.000Z

405

An Auxiliary-Field Quantum Monte Carlo Study of the Chromium Dimer  

E-Print Network [OSTI]

The chromium dimer (Cr2) presents an outstanding challenge for many-body electronic structure methods. Its complicated nature of binding, with a formal sextuple bond and an unusual potential energy curve, is emblematic of the competing tendencies and delicate balance found in many strongly correlated materials. We present a near-exact calculation of the potential energy curve (PEC) and ground state properties of Cr2, using the auxiliary-field quantum Monte Carlo (AFQMC) method. Unconstrained, exact AFQMC calculations are first carried out for a medium-sized but realistic basis set. Elimination of the remaining finite-basis errors and extrapolation to the complete basis set (CBS) limit is then achieved with a combination of phaseless and exact AFQMC calculations. Final results for the PEC and spectroscopic constants are in excellent agreement with experiment.

Purwanto, Wirawan; Krakauer, Henry

2014-01-01T23:59:59.000Z

406

Path-integral solution of the one-dimensional Dirac quantum cellular automaton  

E-Print Network [OSTI]

Quantum cellular automata have been recently considered as a fundamental approach to quantum field theory, resorting to a precise automaton, linear in the field, for the Dirac equation in one dimension. In such linear case a quantum automaton is isomorphic to a quantum walk, and a convenient formulation can be given in terms of transition matrices, leading to a new kind of discrete path integral that we solve analytically in terms of Jacobi polynomials versus the arbitrary mass parameter.

Giacomo Mauro D'Ariano; Nicola Mosco; Paolo Perinotti; Alessandro Tosini

2014-06-04T23:59:59.000Z

407

Effects of internal fields on deep-level emission in InGaN/GaN quantum-well light-emitting diodes  

Science Journals Connector (OSTI)

We report on the important role played by internal quantum well (QW) fields in the anomalous inversion of capacitance transients in InGaN/GaN multi-QW light-emitting diodes (LEDs). This effect was observed by deep-level transient spectroscopy (DLTS) ... Keywords: Deep level, III-Nitride, Internal fields, Quantum well

L. Rigutti; A. Castaldini; A. Cavallini

2009-02-01T23:59:59.000Z

408

Synthesis of linear quantum stochastic systems via quantum feedback networks  

E-Print Network [OSTI]

Recent theoretical and experimental investigations of coherent feedback control, the feedback control of a quantum system with another quantum system, has raised the important problem of how to synthesize a class of quantum systems, called the class of linear quantum stochastic systems, from basic quantum optical components and devices in a systematic way. The synthesis theory sought in this case can be naturally viewed as a quantum analogue of linear electrical network synthesis theory and as such has potential for applications beyond the realization of coherent feedback controllers. In earlier work, Nurdin, James and Doherty have established that an arbitrary linear quantum stochastic system can be realized as a cascade connection of simpler one degree of freedom quantum harmonic oscillators, together with a direct interaction Hamiltonian which is bilinear in the canonical operators of the oscillators. However, from an experimental perspective and based on current methods and technologies, direct interaction Hamiltonians are challenging to implement for systems with more than just a few degrees of freedom. In order to facilitate more tractable physical realizations of these systems, this paper develops a new synthesis algorithm for linear quantum stochastic systems that relies solely on field-mediated interactions, including in implementation of the direct interaction Hamiltonian. Explicit synthesis examples are provided to illustrate the realization of two degrees of freedom linear quantum stochastic systems using the new algorithm.

H. I. Nurdin

2009-05-06T23:59:59.000Z

409

Density-Functional-Theory Calculations of Matter in Strong Magnetic Fields: I. Atoms and Molecules  

E-Print Network [OSTI]

We present new ab initio calculations of the electronic structure of various atoms and molecules in strong magnetic fields ranging from B=10^12 G to 2x10^15 G, appropriate for radio pulsars and magnetars. For these field strengths, the magnetic forces on the electrons dominate over the Coulomb forces, and to a good approximation the electrons are confined to the ground Landau level. Our calculations are based on the density functional theory, and use a local magnetic exchange-correlation function which is tested to be reliable in the strong field regime. Numerical results of the ground-state energies are given for H_N (up to N=10), He_N (up to N=8), C_N (up to N=5) and Fe_N (up to N=3), as well as for various ionized atoms. Fitting formulae for the B-dependence of the energies are also given. In general, as N increases, the binding energy per atom in a molecule, |E_N|/N, increases and approaches a constant value. For all the field strengths considered in this paper, hydrogen, helium, and carbon molecules are found to be bound relative to individual atoms (although for B less than a few x 10^12 G, the relative binding between C and C_2 is small). Iron molecules are not bound at B<10^13 G, but become energetically more favorable than individual atoms at larger field strengths.

Zach Medin; Dong Lai

2007-01-05T23:59:59.000Z

410

Imaging of quantum Hall edge states under quasiresonant excitation by a near-field scanning optical microscope  

SciTech Connect (OSTI)

A high resolution mapping of quantum Hall edge states has been performed by locally creating electrons with small excess energies with a near-field scanning optical microscope in a dilution refrigerator. We have observed fine structures parallel to the edge in photovoltage signals, which appear only at low temperature. The observed fine structures near sample edges have been seen to shift inward with increase in magnetic field in accordance with Chklovskii Shklovskii, and Glazman model.

Ito, H.; Shibata, Y.; Mamyoda, S.; Ootuka, Y.; Nomura, S. [Division of Physics, University of Tsukuba, Tennodai, Tsukuba, 305-8571 (Japan); Kashiwaya, S. [National Institute of Advanced Industrial Science and Technology (AIST), Umezono, Tsukuba, 305-8568 (Japan); Yamaguchi, M.; Akazaki, T.; Tamura, H. [NTT Basic Research Laboratories, NTT Corporation, Morinosato-Wakamiya, Atsugi, 243-0198 (Japan)

2013-12-04T23:59:59.000Z

411

Shear Viscosity in Weakly Coupled N-Component Scalar Field Theories  

E-Print Network [OSTI]

The rich phenomena of the shear viscosity (eta) to entropy density (s) ratio, eta/s, in weakly coupled N-component scalar field theories are studied. eta/s can have a "double dip" behavior due to resonances and the phase transition. If an explicit goldstone mass term is added, then eta/s can either decrease monotonically in temperature or, as seen in many other systems, reach a minimum at the phase transition. We also show how to go beyond the original variational approach to make the Boltzmann equation computation of eta systematic.

Jiunn-Wei Chen; Mei Huang; Chang-Tse Hsieh; Han-Hsin Lin

2010-10-15T23:59:59.000Z

412

Extending the Standard Model Effective Field Theory with the Complete Set of Dimension-7 Operators  

E-Print Network [OSTI]

We present a complete list of the independent dimension-7 operators that are constructed using the Standard Model degrees of freedom and are invariant under the Standard Model gauge group. This list contains only 20 independent operators; far fewer than the 63 operators available at dimension 6. All of these dimension-7 operators contain fermions and violate lepton number, and 7 of the 20 violate baryon number as well. This result extends the Standard Model Effective Field Theory (SMEFT) and allows a more detailed exploration of the structure and properties of possible deformations from the Standard Model Lagrangian.

Landon Lehman

2014-12-26T23:59:59.000Z

413

Effective potential of a black hole in thermal equilibrium with quantum fields  

Science Journals Connector (OSTI)

Expectation values of one-loop renormalized thermal equilibrium stress-energy tensors of free conformal scalars, spin-1/2 fermions, and U(1) gauge fields on a Schwarzschild black hole background are used as sources in the semiclassical Einstein equation. The back reaction and new equilibrium metric have been found at O(?) for each spin field in previous work. In this paper, the nature of the modified black hole spacetime is explored through calculations of the effective potential for null and timelike orbits. Significant novel features affecting the motions of both massive and massless test particles show up at lowest order in ?=(MPl/M)2<1, where M is the black hole mass, and MPl is the Planck mass. Specifically, we find an increase in the black hole capture cross sections, and the existence of a region near the black hole with a repulsive contribution, generated by the U(1) back reaction, to the gravitational force. There is no such effect for other spins. Extrapolating our results suggests a tendency towards the formation of stable circular orbits, but the result cannot be established in O(?): the change in the metric becomes large and it changes its signature. We also consider the back reaction arising from multiple fields, which ultimately should be useful for treating a black hole in equilibrium with field ensembles belonging to gauge theories. In certain circumstances, however, reliable results will require calculations beyond O(?).

David Hochberg; Thomas W. Kephart; James W. York; Jr.

1994-05-15T23:59:59.000Z

414

Quantum Chromodynamics  

Science Journals Connector (OSTI)

The theory of the strong interaction of elementary particles, Quantum Chromodynamics (QCD), is a non-abelian gauge theory with SU(3) as gauge group. The degrees of freedom corresponding to this SU(3) are called c...

Prof. Dr. rer. nat. Manfred Bhm

2001-01-01T23:59:59.000Z

415

Theory of high-power cyclotron-resonance heating in an inhomogeneous magnetic field  

Science Journals Connector (OSTI)

Wave-energy absorption of a plasma due to cyclotron harmonic resonance is evaluated analytically and by a simulation. The static magnetic field is characterized with B??B=0, and a longitudinal wave is supposed to propagate across the magnetic field. In the calculation an orbit modification of the cyclotron motion of particles is taken into account. It is found that the absorption for the fundamental harmonic resonance (m=1) is depressed from that of the conventional linear theory while the absorptions for m?2 are enhanced, where m is the harmonic number. The enhancement is significant when k?t?1 (k the perpendicular wave number and ?t the gyroradius of the thermal particle) and when the interaction time between the plasma particles and the wave exceeds a critical value that is obtainable analytically. For all m and k?t, there appear peaks or saturations in the time evolution of the absorbed energy.

Ryo Sugihara and Yuichi Ogawa

1992-03-15T23:59:59.000Z

416

Nuclear matrix elements in neutrinoless double beta decay: beyond mean-field covariant density functional theory  

E-Print Network [OSTI]

We report a systematic study of nuclear matrix elements (NMEs) in neutrinoless double-beta decays with state-of-the-art beyond mean-field covariant density functional theory. The dynamic effects of particle-number and angular-momentum conservations as well as quadrupole shape fluctuations are taken into account with projections and generator coordinate method for both initial and final nuclei. The full relativistic transition operator is adopted to calculate the NMEs which are found to be consistent with the results of previous beyond non-relativistic mean-field calculation based on a Gogny force with the exception of $^{150}$Nd. Our study shows that the total NMEs can be well approximated by the pure axial-vector coupling term, the calculation of which is computationally much cheaper than that of full terms.

J. M. Yao; L. S. Song; K. Hagino; P. Ring; J. Meng

2014-10-23T23:59:59.000Z

417

Nuclear matrix elements in neutrinoless double beta decay: beyond mean-field covariant density functional theory  

E-Print Network [OSTI]

We report a systematic study of nuclear matrix elements (NMEs) in neutrinoless double-beta decays with state-of-the-art beyond mean-field covariant density functional theory. The dynamic effects of particle-number and angular-momentum conservations as well as quadrupole shape fluctuations are taken into account with projections and generator coordinate method for both initial and final nuclei. The full relativistic transition operator is adopted to calculate the NMEs which are found to be consistent with the results of previous beyond non-relativistic mean-field calculation based on a Gogny force with the exception of $^{150}$Nd. Our study shows that the total NMEs can be well approximated by the pure axial-vector coupling term, the calculation of which is computationally much cheaper than that of full terms.

Yao, J M; Hagino, K; Ring, P; Meng, J

2014-01-01T23:59:59.000Z

418

Oscillator Representation of the BCFT Construction of D-branes in Vacuum String Field Theory  

E-Print Network [OSTI]

Starting from the boundary CFT definition for the D-branes in vacuum string field theory (VSFT) given in hep-th/0105168, we derive the oscillator expression for the D24-brane solution in the VSFT on D25-brane. We show that the state takes the form of a squeezed state, similar to the one found directly in terms of the oscillators and reported in hep-th/0102112. Both the solutions are actually one parameter families of solutions. We also find numerical evidence that at least for moderately large values of the parameter $(b)$ in the oscillator construction the two families of solutions are same under a suitable redefinition of the parameter. Finally we generalize the method to computing the oscillator expression for a D-brane solution with constant gauge field strength turned on along the world volume.

Partha Mukhopadhyay

2001-10-15T23:59:59.000Z

419

Quantum Quandaries: A Category-Theoretic Perspective  

E-Print Network [OSTI]

and water. However, work on topological quantum field theory theory has uncovered a deep analogy between revealed a deep analogy between the two. General relativity makes heavy use of the cat- egory nCob, whose basic concepts. By now it is almost a truism that the project of quantizing gravity may force us

Baez, John

420

Quantum Quandaries: A CategoryTheoretic Perspective  

E-Print Network [OSTI]

and water. However, work on topological quantum field theory theory has uncovered a deep analogy between revealed a deep analogy between the two. General relativity makes heavy use of the cat­ egory nCob, whose basic concepts. By now it is almost a truism that the project of quantizing gravity may force us

Baez, John

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


421

Scintillation has minimal impact on far-field Bennett-Brassard 1984 protocol quantum key distribution  

SciTech Connect (OSTI)

The effect of scintillation, arising from propagation through atmospheric turbulence, on the sift and error probabilities of a quantum key distribution (QKD) system that uses the weak-laser-pulse version of the Bennett-Brassard 1984 (BB84) protocol is evaluated. Two earth-space scenarios are examined: satellite-to-ground and ground-to-satellite transmission. Both lie in the far-field power-transfer regime. This work complements previous analysis of turbulence effects in near-field terrestrial BB84 QKD [J. H. Shapiro, Phys. Rev. A 67, 022309 (2003)]. More importantly, it shows that scintillation has virtually no impact on the sift and error probabilities in earth-space BB84 QKD, something that has been implicitly assumed in prior analyses for that application. This result contrasts rather sharply with what is known for high-speed laser communications over such paths, in which deep, long-lived scintillation fades present a major challenge to high-reliability operation.

Shapiro, Jeffrey H. [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2011-09-15T23:59:59.000Z

422

Quo Vadis Quantum Mechanics?  

Science Journals Connector (OSTI)

Quantum mechanics is one of the most successful theoretical structures in all of science. Developed between 1925-26 to explain the optical spectrum of atoms, the theory over the succeeding 80 years has been extended, first to quantum field theories, gauge field theories, and now even string theory. It is used every day by thousands of physicists to calculate physical phenomena to exquisite precision, with no ambiguity in the results. To claim that this is a theory which is not understood by those physicists is absurd. And yet, as eminent a physicist as Richard Feynman, who did as much as anyone else to extend quantum theory to field theories and was a master at producing those exquisite calculations, could say that anyone who claimed they understood quantum theory clearly did not understand quantum theory. One hundred years ago Einstein postulated one of the most unsettling features of the theory, the wave-particle duality, with his particulate explanation for light of the photoelectric effect, and an explanation which was in direct conflict with Maxwell's brilliant development of a wave, or field, theory of light. Einstein believed that the particulate nature would ultimately be explainable by some sort of non-linear theory of electromagnetism, and was outraged by the acceptance of the community of the probabilistic quantum theory. His programme was of course dealt a (near?) fatal blow by Bell's discovery that the three desiderata - a theory which agrees with experiment, a theory which is local in its effects, and a theory in which nature, at its heart, is not probabilistic - are incompatible. That discomfort felt by Einstein and by Feynman is felt by numerous other people as well. This discomfort is heightened by the fact that the theory of gravity, another of Einstein's great achievements, has resisted all efforts at reconciliation with quantum mechanics. This book explores that discomfort, and tries to pin down what the locus of that discomfort is. For many, the locus is in the probabilistic nature at the heart of the theory. Nature should surely, at some fundamental level, know what it is doing. The photon, despite our inability to measure it, should know where it is and how fast it is going. The papers by t'Hooft, Hiley, and Smolin fall into this camp. Some suspect that the macroscopic world of our immediate sense experiences, and the microscopic world of quantum phenomena, are genuinely different, that the fundamental conceptual nature of physics changes from one to the other, with some unknown boundary between them. Penrose, in his preface alludes to his speculations on this, as does Leggett to his own speculations in his paper. And a number of articles (e.g., by Hartle, Rovelli, and others) opine that if only everyone looked at quantum mechanics in the right way (their way), it would lose its mystery, and be as natural as Newton's world view. (I myself tend to this position, which is however somewhat tempered by the realization that the clarity and naturalness of my viewpoint is not shared by the others who believe equally firmly in their own natural, clear, but radically different, viewpoint). A number of articles simply examine the counterintuitive nature of quantum theory in general, using it to make sense of time travel (Greenberger and Svozil) and demonstrating the unusual features of induction about the past from present observations within quantum theory (Aharonov and Dolev). The book is not free from rather overblown titles (e.g., 'Liberation and Purification from Classical Prejudice', or 'A Quantum Theory of the Human Person') but those articles nevertheless contain at least amusing speculations. In quantum gravity, the incompatibilities between the two masterstrokes of the twentieth century are highlighted. There is a strong suspicion amongst many in this field that progress in understanding quantum gravity demands a deeper understanding of the great mystery of quantum theory which this book explores. This book is a useful and, at times, fascinating introduction to the flounderings which are taking pla

W G Unruh

2006-01-01T23:59:59.000Z

423

Characterizations and Quantifications of Macroscopic Quantumness and Its Implementations using Optical Fields  

E-Print Network [OSTI]

We present a review and discussions on characterizations and quantifications of macroscopic quantum states as well as their implementations and applications in optical systems. We compare and criticize different measures proposed to define and quantify macroscopic quantum superpositions and extend such comparisons to several types of optical quantum states actively considered for experimental implementations within recent research topics.

Hyunseok Jeong; Minsu Kang; Hyukjoon Kwon

2014-07-23T23:59:59.000Z

424

Collapse of integer Hall gaps in a double-quantum-well system  

Science Journals Connector (OSTI)

For coupled double-quantum-well systems in which tunneling is important, the symmetric to antisymmetric energy gap leads to a quantum Hall effect. In this Letter we show that interaction effects in strong magnetic fields can destroy this gap, and present a theory which predicts the occurrence or nonoccurrence of a quantum Hall effect.

A. H. MacDonald; P. M. Platzman; G. S. Boebinger

1990-08-06T23:59:59.000Z

425

Field Theory of the d+t -> n+alpha Reaction Dominated by a 5He* Unstable Particle  

E-Print Network [OSTI]

An effective, non-relativistic field theory for low-energy d+t -> n+alpha reaction is presented. The theory assumes that the reaction is dominated by an intermediate 5He* unstable spin 3/2+ resonance. It involves two parameters in the coupling of the d+t and n+alpha particles to the unstable resonant state, and the resonance energy level -- only three real parameters in all. All Coulomb corrections to this process are computed. The resultant field theory is exactly solvable and provides an excellent description of the d+t fusion process.

Brown, Lowell S

2014-01-01T23:59:59.000Z

426

Physics as quantum information processing  

E-Print Network [OSTI]

The experience from Quantum Information has lead us to look at Quantum Theory (QT) and the whole Physics from a different angle. The information-theoretical paradigm---"It from Bit'---prophesied by John Archibald Wheeler is relentlessly advancing. Recently it has been shown that QT is derivable from pure informational principles. The possibility that there is only QT at the foundations of Physics has been then considered, with space-time, Relativity, quantization rules and Quantum Field Theory (QFT) emerging from a quantum-information processing. The resulting theory is a discrete version of QFT with automatic relativistic invariance, and without fields, Hamiltonian, and quantization rules. In this paper I review some recent advances on these lines. In particular: i) How space-time and relativistic covariance emerge from the quantum computation; ii) The derivation of the Dirac equation as free information flow, without imposing Lorentz covariance; iii) the information-theoretical meaning of inertial mass and Planck constant; iv) An observable consequence of the theory: a mass-dependent refraction index of vacuum. I will then conclude with two possible routes to Quantum Gravity.

Giacomo Mauro D'Ariano

2010-12-12T23:59:59.000Z

427

Effective field theory and keV lines from dark matter  

E-Print Network [OSTI]

We survey operators that can lead to a keV photon line from dark matter decay or annihilation. We are motivated in part by recent claims of an unexplained 3.5 keV line in galaxy clusters and in Andromeda, but our results could apply to any hypothetical line observed in this energy range. We find that given the amount of flux that is observable, explanations in terms of decay are more plausible than annihilation, at least if the annihilation is directly to Standard Model states rather than intermediate particles. The decay case can be explained by a scalar or pseudoscalar field coupling to photons suppressed by a scale not far below the reduced Planck mass, which can be taken as a tantalizing hint of high-scale physics. The scalar case is particularly interesting from the effective field theory viewpoint, and we discuss it at some length. Because of a quartically divergent mass correction, naturalness strongly suggests the theory should be cut off at or below the 1000 TeV scale. The most plausible such natural UV completion would involve supersymmetry. These bottom-up arguments reproduce expectations from top-down considerations of the physics of moduli. A keV line could also arise from the decay of a sterile neutrino, in which case a renormalizable UV completion exists and no direct inference about high-scale physics is possible.

Rebecca Krall; Matthew Reece; Thomas Roxlo

2014-03-05T23:59:59.000Z

428

Effective field theory and keV lines from dark matter  

E-Print Network [OSTI]

We survey operators that can lead to a keV photon line from dark matter decay or annihilation. We are motivated in part by recent claims of an unexplained 3.5 keV line in galaxy clusters and in Andromeda, but our results could apply to any hypothetical line observed in this energy range. We find that given the amount of flux that is observable, explanations in terms of decay are more plausible than annihilation, at least if the annihilation is directly to Standard Model states rather than intermediate particles. The decay case can be explained by a scalar or pseudoscalar field coupling to photons suppressed by a scale not far below the reduced Planck mass, which can be taken as a tantalizing hint of high-scale physics. The scalar case is particularly interesting from the effective field theory viewpoint, and we discuss it at some length. Because of a quartically divergent mass correction, naturalness strongly suggests the theory should be cut off at or below the 1000 TeV scale. The most plausible such natural...

Krall, Rebecca; Roxlo, Thomas

2014-01-01T23:59:59.000Z

429

Magnetic-field effects on quasi-two-dimensional excitons in coupled GaAs?(Ga,Al)As quantum wells  

Science Journals Connector (OSTI)

We have used the variational procedure in the effective-mass and nondegenerate parabolic band approximations in order to investigate the effects of a magnetic field on the exciton effective mass and dispersion in semiconductor heterostructures. Calculations are performed for bulk GaAs, and two-dimensional and quasi-two-dimensional excitons in coupled GaAs?(Ga,Al)As quantum wells for applied magnetic fields perpendicular to the layers. A simple hydrogenlike envelope wave function provides the expected behavior for the exciton dispersion in a wide range of the center-of-mass momenta, and an analytical expression for the exciton effective mass is obtained. Present results lead to a magnetic-field dependent exciton effective mass and dispersion in quite good agreement with available experimental measurements in coupled GaAs?(Ga,Al)As quantum wells.

E. Reyes-Gmez, L. E. Oliveira, and M. de Dios-Leyva

2005-01-14T23:59:59.000Z

430

Wilson Loops and Area-Preserving Diffeomorphisms in Twisted Noncommutative Gauge Theory  

E-Print Network [OSTI]

We use twist deformation techniques to analyse the behaviour under area-preserving diffeomorphisms of quantum averages of Wilson loops in Yang-Mills theory on the noncommutative plane. We find that while the classical gauge theory is manifestly twist covariant, the holonomy operators break the quantum implementation of the twisted symmetry in the usual formal definition of the twisted quantum field theory. These results are deduced by analysing general criteria which guarantee twist invariance of noncommutative quantum field theories. From this a number of general results are also obtained, such as the twisted symplectic invariance of noncommutative scalar quantum field theories with polynomial interactions and the existence of a large class of holonomy operators with both twisted gauge covariance and twisted symplectic invariance.

Mauro Riccardi; Richard J. Szabo

2007-01-30T23:59:59.000Z

431

Wilson loops and area-preserving diffeomorphisms in twisted noncommutative gauge theory  

SciTech Connect (OSTI)

We use twist deformation techniques to analyze the behavior under area-preserving diffeomorphisms of quantum averages of Wilson loops in Yang-Mills theory on the noncommutative plane. We find that while the classical gauge theory is manifestly twist covariant, the holonomy operators break the quantum implementation of the twisted symmetry in the usual formal definition of the twisted quantum field theory. These results are deduced by analyzing general criteria which guarantee twist invariance of noncommutative quantum field theories. From this a number of general results are also obtained, such as the twisted symplectic invariance of noncommutative scalar quantum field theories with polynomial interactions and the existence of a large class of holonomy operators with both twisted gauge covariance and twisted symplectic invariance.

Riccardi, Mauro; Szabo, Richard J. [Department of Mathematics and Maxwell Institute for Mathematical Sciences, Heriot-Watt University, Colin Maclaurin Building, Riccarton, Edinburgh EH14 4AS (United Kingdom)

2007-06-15T23:59:59.000Z

432

Excitonic enhancement of nonradiative energy transfer from a quantum well in the optical near field of energy gradient quantum dots  

E-Print Network [OSTI]

. Phys. 111, 113714 (2012) Transport of indirect excitons in a potential energy gradient Appl. Phys. Lett 30 April 2012; published online 13 June 2012) We report strong exciton migration with an efficiency (QWs) to colloidal nanocrystal quantum dots (NQDs) is criti- cal to the energy efficiency in hybrid

Demir, Hilmi Volkan

433

How well do mean field theories of spiking quadratic-integrate-and-fire networks work in realistic parameter regimes?  

Science Journals Connector (OSTI)

We use mean field techniques to compute the distribution of excitatory and inhibitory firing rates in large networks of randomly connected spiking quadratic integrate and fire neurons. These techniques are based on the assumption that activity is asynchronous ... Keywords: Mean field theory, Quadratic integrate and fire neuron, Random networks, Recurrent network, Synchronization, Theta neuron

Agnieszka Grabska-Barwi?ska; Peter E. Latham

2014-06-01T23:59:59.000Z

434

AdS/CFT and Light-Front Holography: A Theory of Strong Interactions  

SciTech Connect (OSTI)

Recent developments in the theory of strong interactions are discussed in the framework of the AdS/CFT duality between string theories of gravity in a higher dimension Anti-de Sitter space and conformal quantum field theories in physical space-time. This novel theoretical approach, combined with 'light-front holography', leads to new insights into the quark and gluon structure of hadrons and a viable first approximation to quantum chromodynamics, the fundamental theory of the strong and nuclear interactions.

Brodsky, Stanley J.; /SLAC; Teramond, Guy F.de; /Costa Rica U.

2009-02-23T23:59:59.000Z

435

On a super-selection rule in quantum cosmology  

E-Print Network [OSTI]

The discarding of negative frequency solutions in a quantum field theory brings about the absence of antiparticles which, after all, means the violation of 4-inversion symmetry $(x \\rightarrow -x, t \\rightarrow-t)$ which is a (improper) Lorentz transformation. Suppose you have a theory of quantum gravity which lacks the negative frequency solutions (like usually people have in quantum cosmology, invoking a super-selection rule). Taking some limit in this theory in order to obtain the weak (or null) gravitational regime, the result is a theory that does not respect that symmetry and does not have place for antiparticles. That is, a theory of fields is not obtained, as it should be. For the case of a quantum cosmology model we show that if we ignore the negative frequency solutions, the rich processes of creation/annihilation of universes at the Planck scale, are lost.

E. Sergio Santini

2014-12-26T23:59:59.000Z

436

Population Transfer between Two Quantum States by Piecewise Chirping of Femtosecond Pulses: Theory and Experiment  

SciTech Connect (OSTI)

We propose and experimentally demonstrate the method of population transfer by piecewise adiabatic passage between two quantum states. Coherent excitation of a two-level system with a train of ultrashort laser pulses is shown to reproduce the effect of an adiabatic passage, conventionally achieved with a single frequency-chirped pulse. By properly adjusting the amplitudes and phases of the pulses in the excitation pulse train, we achieve complete and robust population transfer to the target state. The piecewise nature of the process suggests a possibility for the selective population transfer in complex quantum systems.

Zhdanovich, S. [Departments of Physics and Astronomy, University of British Columbia, Vancouver (Canada); Laboratory for Advanced Spectroscopy and Imaging Research (LASIR), University of British Columbia, Vancouver (Canada); Shapiro, E. A. [Chemistry, University of British Columbia, Vancouver (Canada); Shapiro, M.; Hepburn, J. W.; Milner, V. [Departments of Physics and Astronomy, University of British Columbia, Vancouver (Canada); Chemistry, University of British Columbia, Vancouver (Canada); Laboratory for Advanced Spectroscopy and Imaging Research (LASIR), University of British Columbia, Vancouver (Canada)

2008-03-14T23:59:59.000Z

437

Surface Tension of Electrolyte Interfaces: Ionic Specificity within a Field-Theory Approach  

E-Print Network [OSTI]

We study the surface tension of ionic solutions at air/water and oil/water interfaces. By using field-theoretical methods and including a finite proximal surface-region with ionic-specific interactions. The free energy is expanded to first-order in a loop expansion beyond the mean-field result. We calculate the excess surface tension and obtain analytical predictions that reunite the Onsager-Samaras pioneering result (which does not agree with experimental data), with the ionic specificity of the Hofmeister series. We derive analytically the surface-tension dependence on the ionic strength, ionic size and ion-surface interaction, and show consequently that the Onsager-Samaras result is consistent with the one-loop correction beyond the mean-field result. Our theory fits well a wide range of salt concentrations for different monovalent ions using one fit parameter, and reproduces the reverse Hofmeister series for anions at the air/water and oil/water interfaces.

Markovich, Tomer; Podgornik, Rudolf

2014-01-01T23:59:59.000Z

438

Surface Tension of Electrolyte Interfaces: Ionic Specificity within a Field-Theory Approach  

E-Print Network [OSTI]

We study the surface tension of ionic solutions at air/water and oil/water interfaces. By using field-theoretical methods and including a finite proximal surface-region with ionic-specific interactions. The free energy is expanded to first-order in a loop expansion beyond the mean-field result. We calculate the excess surface tension and obtain analytical predictions that reunite the Onsager-Samaras pioneering result (which does not agree with experimental data), with the ionic specificity of the Hofmeister series. We derive analytically the surface-tension dependence on the ionic strength, ionic size and ion-surface interaction, and show consequently that the Onsager-Samaras result is consistent with the one-loop correction beyond the mean-field result. Our theory fits well a wide range of salt concentrations for different monovalent ions using one fit parameter per electrolyte, and reproduces the reverse Hofmeister series for anions at the air/water and oil/water interfaces.

Tomer Markovich; David Andelman; Rudolf Podgornik

2015-01-10T23:59:59.000Z

439

Microtoroid cavity QED with fiber overcoupling and strong atom-field coupling: a single-atom quantum switch for coherent light fields  

E-Print Network [OSTI]

We propose a scheme for single-atom, quantum control of the direction of propagation of a coherent field incident, via a tapered fiber, upon a microtoroidal whispering-gallery-mode (WGM) resonator. The scheme involves overcoupling of the fiber-taper to the resonator and strong coupling of an atom to the evanescent field of the WGM, i.e., an atom-field coupling that exceeds the total WGM linewidth. In contrast to previous, related schemes that operate in the bad-cavity regime, the proposed scheme can operate effectively with much stronger incident fields, while also preserving their coherent nature. It can also serve to prepare an entangled state of the atom and coherent optical pulses propagating in opposite directions along the fiber. We evaluate the fidelity of preparation of such a state taking into account absorption and atomic spontaneous emission and demonstrate that high fidelities should be possible with realistic parameters.

Scott Parkins; Takao Aoki

2014-11-21T23:59:59.000Z

440

Non-Abelian Gauge Fields. Relativistic Invariance  

Science Journals Connector (OSTI)

A simple criterion for Lorentz invariance in quantum field theory is stated as a commutator condition relating the energy density to the momentum density. With its aid a relativistically invariant radiation-gauge formulation is devised for a non-Abelian vector-gauge field coupled to a spin- Fermi field.

Julian Schwinger

1962-07-01T23:59:59.000Z

Note: This page contains sample records for the topic "quantum field theory" from the National Library of EnergyBeta (NLEBeta).
While these samples are representative of the content of NLEBeta,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of NLEBeta
to obtain the most current and comprehensive results.


441

Singlet and triplet states of trions in ZuSe-based quantum wells probed by magnetic fields to 50 Tesla  

SciTech Connect (OSTI)

Singlet and triplet states of positively (X{sup +}) and negatively (X{sup -}) charged excitons in ZnSe-based quantum wells have been studied by means of photoluminescence in pulsed magnetic fields up to 50 T. The binding energy of the X{sup -} singlet state shows a monotonic increase with magnetic field with a tendency to saturation, while that of the X{sup +} slightly decreases. The triplet X{sup +} and X{sup -} states, being unbound at zero magnetic field, noticeably increase their binding energy in high magnetic fields. The experimental evidence for the interaction between the triplet and singlet states of lTions leading to their anticrossing in magnetic fields has been found.

Astakhov, G. V.; Yakovlev, D. R.; Crooker, S. A. (Scott A.); Barrick, T. (Todd); Dzyubenko, A. B.; Sander, Thomas; Kochereshko, V. P.; Ossau, W.; Faschinger, W.; Waag, A.

2002-01-01T23:59:59.000Z

442

Integrable anyon chains: from fusion rules to face models to effective field theories  

E-Print Network [OSTI]

Starting from the fusion rules for the algebra $SO(5)_2$ we construct one-dimensional lattice models of interacting anyons with commuting transfer matrices of `interactions round the face' (IRF) type. The conserved topological charges of the anyon chain are recovered from the transfer matrices in the limit of large spectral parameter. The properties of the models in the thermodynamic limit and the low energy excitations are studied using Bethe ansatz methods. Two of the anyon models are critical at zero temperature. From the analysis of the finite size spectrum we find that they are effectively described by rational conformal field theories invariant under extensions of the Virasoro algebra, namely $\\mathcal{W}B_2$ and $\\mathcal{W}D_5$, respectively. The latter contains primaries with half and quarter spin. The modular partition function and fusion rules are derived and found to be consistent with the results for the lattice model.

Peter E. Finch; Michael Flohr; Holger Frahm

2014-08-06T23:59:59.000Z

443

Integrable anyon chains: from fusion rules to face models to effective field theories  

E-Print Network [OSTI]

Starting from the fusion rules for the algebra $SO(5)_2$ we construct one-dimensional lattice models of interacting anyons with commuting transfer matrices of `interactions round the face' (IRF) type. The conserved topological charges of the anyon chain are recovered from the transfer matrices in the limit of large spectral parameter. The properties of the models in the thermodynamic limit and the low energy excitations are studied using Bethe ansatz methods. Two of the anyon models are critical at zero temperature. From the analysis of the finite size spectrum we find that they are effectively described by rational conformal field theories invariant under extensions of the Virasoro algebra, namely $\\mathcal{W}B_2$ and $\\mathcal{W}D_5$, respectively. The latter contains primaries with half and quarter spin. The modular partition function and fusion rules are derived and found to be consistent with the results for the lattice model.

Finch, Peter E; Frahm, Holger

2014-01-01T23:59:59.000Z

444

N=2 minimal conformal field theories and matrix bifactorisations of x^d  

E-Print Network [OSTI]

We prove a tensor equivalence between full subcategories of a) graded matrix factorisations of the potential x^d-y^d and b) representations of the N=2 minimal super vertex operator algebra at central charge 3-6/d, where d is odd. The subcategories are given by a) permutation-type matrix factorisations with consecutive index sets, and b) Neveu-Schwarz-type representations. The physical motivation for this result is the Landau-Ginzburg / conformal field theory correspondence, where it amounts to the equivalence of a subset of defects on both sides of the correspondence. Our work builds on results by Brunner and Roggenkamp [arXiv:0707.0922], where an isomorphism of fusion rules was established.

Davydov, Alexei; Runkel, Ingo

2014-01-01T23:59:59.000Z

445

N=2 minimal conformal field theories and matrix bifactorisations of x^d  

E-Print Network [OSTI]

We prove a tensor equivalence between full subcategories of a) graded matrix factorisations of the potential x^d-y^d and b) representations of the N=2 minimal super vertex operator algebra at central charge 3-6/d, where d is odd. The subcategories are given by a) permutation-type matrix factorisations with consecutive index sets, and b) Neveu-Schwarz-type representations. The physical motivation for this result is the Landau-Ginzburg / conformal field theory correspondence, where it amounts to the equivalence of a subset of defects on both sides of the correspondence. Our work builds on results by Brunner and Roggenkamp [arXiv:0707.0922], where an isomorphism of fusion rules was established.

Alexei Davydov; Ana Ros Camacho; Ingo Runkel

2014-09-07T23:59:59.000Z

446

Green's function method for single-particle resonant states in relativistic mean field theory  

Science Journals Connector (OSTI)

Relativistic mean field theory is formulated with the Green's function method in coordinate space to investigate the single-particle bound states and resonant states on the same footing. Taking the density of states for free particles as a reference, the energies and widths of single-particle resonant states are extracted from the density of states without any ambiguity. As an example, the energies and widths for single-neutron resonant states in 120Sn are compared with those obtained by the scattering phase-shift method, the analytic continuation in the coupling constant approach, the real stabilization method, and the complex scaling method. Excellent agreements with these methods are found for the energies and widths of single-neutron resonant states.

T. T. Sun (???); S. Q. Zhang (???); Y. Zhang (??); J. N. Hu (???); J. Meng (??)

2014-11-18T23:59:59.000Z

447

Analysis of park-and-ride decision behavior based on Decision Field Theory  

Science Journals Connector (OSTI)

Park and ride is a kind of traffic management solution to the traffic congestion problem in urban cities. This paper analyzes the decision making behavior of Park and Ride from a psychological point of view. Decision Field Theory is used to establish the decision model of Park and Ride. The proposed decision model is calibrated using real-life experimental survey data and has proved to be able to account for the complex decision behavior processes observed in the experimental survey data. The model demonstrates the psychological decision processes of individual travelers and the decision characteristics, such as simple decision, indecision and preference reversal. The effects of factors, e.g. deliberation time, deliberation threshold and initial preference, for mode choice are also examined. The proposed model demonstrates its capability of analyzing park-and-ride decision behavior and providing policy makers with useful information for future promotion and planning for park-and-ride facilities.

Huanmei Qin; Hongzhi Guan; Yao-Jan Wu

2013-01-01T23:59:59.000Z

448

Quantum Simulation  

E-Print Network [OSTI]

Simulating quantum mechanics is known to be a difficult computational problem, especially when dealing with large systems. However, this difficulty may be overcome by using some controllable quantum system to study another less controllable or accessible quantum system, i.e., quantum simulation. Quantum simulation promises to have applications in the study of many problems in, e.g., condensed-matter physics, high-energy physics, atomic physics, quantum chemistry and cosmology. Quantum simulation could be implemented using quantum computers, but also with simpler, analog devices that would require less control, and therefore, would be easier to construct. A number of quantum systems such as neutral atoms, ions, polar molecules, electrons in semiconductors, superconducting circuits, nuclear spins and photons have been proposed as quantum simulators. This review outlines the main theoretical and experimental aspects of quantum simulation and emphasizes some of the challenges and promises of this fast-growing field.

I. M. Georgescu; S. Ashhab; Franco Nori

2014-03-13T23:59:59.000Z

449

Extending the predictive power and scope of electronic structure theory and quantum transport  

E-Print Network [OSTI]

The day 1998 Nobel Prize recipient Walter Kohn wrote his first article on Density Functional Theory, he could never have predicted its eventual impact on computational materials science. Almost 50 years after his original ...

Poilvert, Nicolas (Nicolas Alain Pierre-Yves)

2011-01-01T23:59:59.000Z

450

Manifestations of quantum phase transitions in transport through nanosystems  

SciTech Connect (OSTI)

The award led to several important new results in theory of interacting low-dimensional systems. The results are relevant for both traditional condensed matter systems, such as quantum wires and quantum spin chains, and for the relatively new field of ultra-cold atomic gases.

Pustilnik, Michael

2014-08-28T23:59:59.000Z

451

Direct and indirect exciton states in GaAs-(Ga, Al)As double quantum wells under crossed electric and magnetic fields  

Science Journals Connector (OSTI)

A theoretical study of the direct and indirect exciton states in GaAs/Ga1-xAlxAs coupled double quantum wells under crossed electric and magnetic fields is presented. The setup of the system under consideration consists of an ... Keywords: 71.55.Eq, 73.20.Mf, 73.21.Fg, Diamagnetic shifts, Double quantum-wells, Magnetoexcitons

L. E. Oliveira; M. de Dios-Leyva; C. A. Duque

2008-03-01T23:59:59.000Z

452

Exciton diamagnetic shift in GaAs/Ga1-xAlxAs quantum wells under in-plane magnetic fields  

Science Journals Connector (OSTI)

Using a variational procedure in the effective-mass and parabolic-band approximations we investigate the effects of in-plane magnetic fields on the exciton states in single GaAs/Ga1-xAlxAs quantum wells. Exciton properties ... Keywords: 71.55.Eq, 73.20.Mf, 73.21.Fg, Diamagnetic shifts, Magnetoexcitons, Quantum wells

C. A. Duque; M. de Dios-Leyva; L. E. Oliveira

2008-03-01T23:59:59.000Z

453

EPR states and Bell correlated states in algebraic quantum field theory  

E-Print Network [OSTI]

A mathematical rigorous definition of EPR states has been introduced by Arens and Varadarajan for finite dimensional systems, and extended by Werner to general systems. In the present paper we follow a definition of EPR states due to Werner. Then we show that an EPR state for incommensurable pairs is Bell correlated, and that the set of EPR states for incommensurable pairs is norm dense between two strictly space-like separated regions.

Yuichiro Kitajima

2013-04-18T23:59:59.000Z

454

Negative magnetic eddy diffusivities from test-field method and multiscale stability theory  

E-Print Network [OSTI]

The generation of large-scale magnetic field in the kinematic regime in the absence of an alpha-effect is investigated by following two different approaches, namely the test-field method and multiscale stability theory relying on the homogenisation technique. We show analytically that the former, applied for the evaluation of magnetic eddy diffusivities, yields results that fully agree with the latter. Our computations of the magnetic eddy diffusivity tensor for the specific instances of the parity-invariant flow-IV of G.O. Roberts and the modified Taylor-Green flow in a suitable range of parameter values confirm the findings of previous studies, and also explain some of their apparent contradictions. The two flows have large symmetry groups; this is used to considerably simplify the eddy diffusivity tensor. Finally, a new analytic result is presented: upon expressing the eddy diffusivity tensor in terms of solutions to auxiliary problems for the adjoint operator, we derive relations between magnetic eddy dif...

Andrievsky, Alexander; Noullez, Alain; Zheligovsky, Vladislav

2015-01-01T23:59:59.000Z

455

Chiral Quantum Walks  

E-Print Network [OSTI]

Wigner separated the possible types of symmetries in quantum theory into those symmetries that are unitary and those that are antiunitary. Unitary symmetries have been well studied whereas antiunitary symmetries and the physical implications associated with time-reversal symmetry breaking have had little influence on quantum information science. Here we develop a quantum circuits version of time-reversal symmetry theory, classifying time-symmetric and time-asymmetric Hamiltonians and circuits in terms of their underlying network elements and geometric structures. These results reveal that many of the typical quantum circuit networks found across the field of quantum information science exhibit time-asymmetry. We then experimentally implement the most fundamental time-reversal asymmetric process, applying local gates in an otherwise time-symmetric circuit to induce time-reversal asymmetry and thereby achieve (i) directional biasing in the transition probability between basis states, (ii) the enhancement of and (iii) the suppression of these transport probabilities. Our results imply that the physical effect of time-symmetry breaking plays an essential role in coherent transport and its control represents an omnipresent yet essentially untapped resource in quantum transport science.

DaWei Lu; Jacob D. Biamonte; Jun Li; Hang Li; Tomi H. Johnson; Ville Bergholm; Mauro Faccin; Zoltn Zimbors; Raymond Laflamme; Jonathan Baugh; Seth Lloyd

2014-05-23T23:59:59.000Z

456

Transitivity vs. Intransitivity in decision making process. (An example in quantum game theory)  

E-Print Network [OSTI]

We compare two different ways of quantization a simple sequential game Cat's Dilemma in the context of the debate on intransitive and transitive preferences. This kind of analysis can have essential meaning for the research on the artificial intelligence (some possibilities are discussed). Nature has both properties transitive and intransitive and maybe quantum models can be more able to capture this dualism than classical one. We also present electoral interpretation of the game.

Marcin Makowski

2009-01-12T23:59:59.000Z

457

Quantum Theory of Transmission Line Resonator-Assisted Cooling of a Micromechanical Resonator  

E-Print Network [OSTI]

We propose a quantum description of the cooling of a micromechanical flexural oscillator by a one-dimensional transmission line resonator via a force that resembles cavity radiation pressure. The mechanical oscillator is capacitively coupled to the central conductor of the transmission line resonator. At the optimal point, the micromechanical oscillator can be cooled close to the ground state, and the cooling can be measured by homodyne detection of the output microwave signal.

Yong Li; Ying-Dan Wang; Fei Xue; C. Bruder

2008-04-30T23:59:59.000Z

458

Quantum theory of optical temporal phase and instantaneous frequency. II. Continuous-time limit and state-variable approach to phase-locked loop design  

SciTech Connect (OSTI)

We consider the continuous-time version of our recently proposed quantum theory of optical temporal phase and instantaneous frequency [M. Tsang et al., Phys. Rev. A 78, 053820 (2008)]. Using a state-variable approach to estimation, we design homodyne phase-locked loops that can measure the temporal phase with quantum-limited accuracy. We show that postprocessing can further improve the estimation performance if delay is allowed in the estimation. We also investigate the fundamental uncertainties in the simultaneous estimation of harmonic-oscillator position and momentum via continuous optical phase measurements from the classical estimation theory perspective. In the case of delayed estimation, we find that the inferred uncertainty product can drop below that allowed by the Heisenberg uncertainty relation. Although this result seems counterintuitive, we argue that it does not violate any basic principle of quantum mechanics.

Tsang, Mankei; Shapiro, Jeffrey H. [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Lloyd, Seth [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Department of Mechanic