Ultrasonic hydrometer. [Specific gravity of electrolyte
Swoboda, C.A.
1982-03-09T23:59:59.000Z
The disclosed ultrasonic hydrometer determines the specific gravity (density) of the electrolyte of a wet battery, such as a lead-acid battery. The hydrometer utilizes a transducer that when excited emits an ultrasonic impulse that traverses through the electrolyte back and forth between spaced sonic surfaces. The transducer detects the returning impulse, and means measures the time t between the initial and returning impulses. Considering the distance d between the spaced sonic surfaces and the measured time t, the sonic velocity V is calculated with the equation V = 2d/t. The hydrometer also utilizes a thermocouple to measure the electrolyte temperature. A hydrometer database correlates three variable parameters including sonic velocity in and temperature and specific gravity of the electrolyte, for temperature values between 0 and 40/sup 0/C and for specific gravity values between 1.05 and 1.30. Upon knowing two parameters (the calculated sonic velocity and the measured temperature), the third parameter (specific gravity) can be uniquely found in the database. The hydrometer utilizes a microprocessor for data storage and manipulation.
King, Anthony Laurence
1974-01-01T23:59:59.000Z
. , Texas ASM University; Chairman of Advisory Committee: Dr. David M, Moehring In this study wood specific gravity values of 220 plantation grown slash pine (Pinus elliottii Engelm. ) trees growing in East Texas were calculated and related to tree... parameters. Also tree dry weight (DW) relationships with tree parameters were determined and dry weight tables calculated. Average specific gravity values of cores and disks at breast height and tree specific gravities respectively were 0. 457, 0. 493...
New correlations for dew-point, specific gravity and producing yield for gas condensates
Ovalle Cortissoz, Adriana Patricia
2002-01-01T23:59:59.000Z
This work presents four newly developed correlations to estimate dew-point pressure, current specific gravity and producing yield of gas condensate reservoirs. The first correlation may be used to predict the dew-point pressure of the reservoir gas...
134 Solutions Manual x Fluid Mechanics, Fifth Edition 2.103 A solid block, of specific gravity
Bahrami, Majid
134 Solutions Manual x Fluid Mechanics, Fifth Edition 2.103 A solid block, of specific gravity 0.9, floats such that 75% of its volume is in water and 25% of its volume is in fluid X, which is layered above the water. What is the specific gravity of fluid X? Solution: The block is sketched at right
Kennedy, Matthew joseph
2009-05-15T23:59:59.000Z
The objective of this study was to evaluate the effect of orally administered ammonium chloride (NH4CL) on pH and specific gravity of urine, overall gain, and water consumption in mature wethers on a grower/finisher ration. Obstructive urolithiasis...
Massive gravity from bimetric gravity
Baccetti, Valentina; Visser, Matt
2012-01-01T23:59:59.000Z
We discuss the subtle relationship between so-called massive gravity (that is, gravity incorporating a non-zero graviton mass) and bimetric gravity, focussing particularly on the manner in which massive gravity may be viewed as a suitable limit of bimetric gravity. The limiting procedure is more delicate than currently appreciated, and in particular, in a cosmological context can lead to an interesting interplay between the "background" and "foreground" metrics. The fact that in bimetric theories one always has two sets of metric equations of motion, one for each metric, continues to have an effect even in the massive gravity limit. Thus, solutions of bimetric gravity in the limit of vanishing kinetic term are also solutions of massive gravity, but the contrary statement is not necessarily true.
Lujan, Richard E. (Santa Fe, NM)
2001-01-01T23:59:59.000Z
A mechanical gravity brake that prevents hoisted loads within a shaft from free-falling when a loss of hoisting force occurs. A loss of hoist lifting force may occur in a number of situations, for example if a hoist cable were to break, the brakes were to fail on a winch, or the hoist mechanism itself were to fail. Under normal hoisting conditions, the gravity brake of the invention is subject to an upward lifting force from the hoist and a downward pulling force from a suspended load. If the lifting force should suddenly cease, the loss of differential forces on the gravity brake in free-fall is translated to extend a set of brakes against the walls of the shaft to stop the free fall descent of the gravity brake and attached load.
B. L. Hu
1999-02-22T23:59:59.000Z
We give a summary of the status of current research in stochastic semiclassical gravity and suggest directions for further investigations. This theory generalizes the semiclassical Einstein equation to an Einstein-Langevin equation with a stochastic source term arising from the fluctuations of the energy-momentum tensor of quantum fields. We mention recent efforts in applying this theory to the study of black hole fluctuations and backreaction problems, linear response of hot flat space, and structure formation in inflationary cosmology. To explore the physical meaning and implications of this stochastic regime in relation to both classical and quantum gravity, we find it useful to take the view that semiclassical gravity is mesoscopic physics and that general relativity is the hydrodynamic limit of certain spacetime quantum substructures. Three basic issues - stochasticity, collectivity, correlations- and three processes - dissipation, fluctuations, decoherence- underscore the transformation from quantum micro structure and interaction to the emergence of classical macro structure and dynamics. We discuss ways to probe into the high energy activity from below and make two suggestions: via effective field theory and the correlation hierarchy. We discuss how stochastic behavior at low energy in an effective theory and how correlation noise associated with coarse-grained higher correlation functions in an interacting quantum field could carry nontrivial information about the high energy sector. Finally we describe processes deemed important at the Planck scale, including tunneling and pair creation, wave scattering in random geometry, growth of fluctuations and forms, Planck scale resonance states, and spacetime foams.
Surface gravities for non-Killing horizons
Cropp, Bethan; Visser, Matt
2013-01-01T23:59:59.000Z
There are many logically and computationally distinct characterizations of the surface gravity of a horizon, just as there are many logically rather distinct notions of horizon. Fortunately, in standard general relativity, for stationary horizons, most of these characterizations are degenerate. However, in modified gravity, or in analogue spacetimes, horizons may be non-Killing or even non-null, and hence these degeneracies can be lifted. We present a brief overview of the key issues, specifically focusing on horizons in analogue spacetimes and universal horizons in modified gravity.
Rong-Jia Yang
2014-09-11T23:59:59.000Z
If we assume that the source of thermodynamic system, $\\rho$ and $p$, are also the source of gravity, thermal quantities, such as entropy, temperature, and chemical potential, can induce effects of gravity, or gravity can induce thermal effects. We find only for systems with constant temperature and zero chemical potential, gravity can be seen as an entropic force. The case for Newtonian approximation is discussed.
Quantum Gravity and Precision Tests
C. P. Burgess
2006-06-24T23:59:59.000Z
This article provides a cartoon of the quantization of General Relativity using the ideas of effective field theory. These ideas underpin the use of General Relativity as a theory from which precise predictions are possible, since they show why quantum corrections to standard classical calculations are small. Quantum corrections can be computed controllably provided they are made for the weakly-curved geometries associated with precision tests of General Relativity, such as within the solar system or for binary pulsars. They also bring gravity back into the mainstream of physics, by showing that its quantization (at low energies) exactly parallels the quantization of other, better understood, non-renormalizable field theories which arise elsewhere in physics. Of course effective field theory techniques do not solve the fundamental problems of quantum gravity discussed elsewhere in these pages, but they do helpfully show that these problems are specific to applications on very small distance scales. They also show why we may safely reject any proposals to modify gravity at long distances if these involve low-energy problems (like ghosts or instabilities), since such problems are unlikely to be removed by the details of the ultimate understanding of gravity at microscopic scales.
Fab 5: noncanonical kinetic gravity, self tuning, and cosmic acceleration
Appleby, Stephen A.; Linder, Eric V. [Institute for the Early Universe WCU, Ewha Womans University, Seoul (Korea, Republic of); Felice, Antonio De, E-mail: stephen.appleby@ewha.ac.kr, E-mail: adefelic@gmail.com, E-mail: evlinder@lbl.gov [ThEP's CRL, NEP, The Institute for Fundamental Study, Naresuan University, Phitsanulok 65000 (Thailand)
2012-10-01T23:59:59.000Z
We investigate circumstances under which one can generalize Horndeski's most general scalar-tensor theory of gravity. Specifically we demonstrate that a nonlinear combination of purely kinetic gravity terms can give rise to an accelerating universe without the addition of extra propagating degrees of freedom on cosmological backgrounds, and exhibit self tuning to bring a large cosmological constant under control. This nonlinear approach leads to new properties that may be instructive for exploring the behaviors of gravity.
Quantization of Emergent Gravity
Hyun Seok Yang
2014-12-24T23:59:59.000Z
Emergent gravity is based on a novel form of the equivalence principle known as the Darboux theorem or the Moser lemma in symplectic geometry stating that the electromagnetic force can always be eliminated by a local coordinate transformation as far as spacetime admits a symplectic structure, in other words, a microscopic spacetime becomes noncommutative (NC). If gravity emerges from U(1) gauge theory on NC spacetime, this picture of emergent gravity suggests a completely new quantization scheme where quantum gravity is defined by quantizing spacetime itself, leading to a dynamical NC spacetime. Therefore the quantization of emergent gravity is radically different from the conventional approach trying to quantize a phase space of metric fields. This approach for quantum gravity allows a background independent formulation where spacetime as well as matter fields is equally emergent from a universal vacuum of quantum gravity.
Bounds on quantum communication via Newtonian gravity
D. Kafri; G. J. Milburn; J. M. Taylor
2014-10-08T23:59:59.000Z
Newtonian gravity yields specific observable consequences, the most striking of which is the emergence of a $1/r^2$ force. In so far as communication can arise via such interactions between distant particles, we can ask what would be expected for a theory of gravity that only allows classical communication. Many heuristic suggestions for gravity-induced decoherence have this restriction implicitly or explicitly in their construction. Here we show that communication via a $1/r^2$ force has a minimum noise induced in the system when the communication cannot convey quantum information, in a continuous time analogue to Bell's inequalities. Our derived noise bounds provide tight constraints from current experimental results on any theory of gravity that does not allow quantum communication.
Wavelet based inversion of gravity data Fabio Boschetti
Boschetti, Fabio
1 Wavelet based inversion of gravity data Fabio Boschetti CSIRO Exploration & Mining and Australian Running Heading: Wavelet based inversion of gravity data #12;2 ABSTRACT The Green's function of the Poisson equation, and its spatial derivatives, lead to a family of wavelets specifically tailored
Felix M. Lev
2010-05-16T23:59:59.000Z
We consider a possibility that gravity is not an interaction but a manifestation of a symmetry based on a Galois field.
The shape dynamics description of gravity
Tim Koslowski
2015-01-13T23:59:59.000Z
Classical gravity can be described as a relational dynamical system without ever appealing to spacetime or its geometry. This description is the so-called shape dynamics description of gravity. The existence of relational first principles from which the shape dynamics description of gravity can be derived is a motivation to consider shape dynamics (rather than GR) as the fundamental description of gravity. Adopting this point of view leads to the question: What is the role of spacetime in the shape dynamics description of gravity? This question contains many aspects: Compatibility of shape dynamics with the description of gravity in terms of spacetime geometry, the role of local Minkowski space, universality of spacetime geometry and the nature of quantum particles, which can no longer be assumed to be irreducible representations of the Poincare group. In this contribution I derive effective spacetime structures by considering how matter fluctuations evolve along with shape dynamics. This evolution reveals an "experienced spacetime geometry." This leads (in an idealized approximation) to local Minkowski space and causal relations. The small scale structure of the emergent geometric picture depends on the specific probes used to experience spacetime, which limits the applicability of effective spacetime to describe shape dynamics. I conclude with discussing the nature of quantum fluctuations (particles) in shape dynamics and how local Minkowski spacetime emerges from the evolution of quantum particles.
Counterterms in Massive Gravity Theory
Cao, Li-Ming
2015-01-01T23:59:59.000Z
We derived local boundary counterterms in massive gravity theory with a negative cosmological constant in four dimensions. With these counterterms at hand we analyzed the properties of the boundary field theory in the context of AdS/CFT duality by calculating the boundary stress energy tensor. The calculation shows that the boundary stress energy tensor is conserved, and momentum dissipation might occur on the level of linear response only. We also calculated the thermodynamic quantities and the boundary stress energy tensor for a specific type of solutions. The thermodynamic potentials agree with the results of literature up to some constants which can be removed by adding finite counterterms.
Particle Dynamics And Emergent Gravity
Amir H. Fatollahi
2008-05-08T23:59:59.000Z
The emergent gravity proposal is examined within the framework of noncommutative QED/gravity correspondence from particle dynamics point of view.
Entropic force, noncommutative gravity, and ungravity
Nicolini, Piero [Frankfurt Institute for Advanced Studies (FIAS), Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Ruth-Moufang-Strasse 1, 60438 Frankfurt am Main (Germany)
2010-08-15T23:59:59.000Z
After recalling the basic concepts of gravity as an emergent phenomenon, we analyze the recent derivation of Newton's law in terms of entropic force proposed by Verlinde. By reviewing some points of the procedure, we extend it to the case of a generic quantum gravity entropic correction to get compelling deviations to the Newton's law. More specifically, we study: (1) noncommutative geometry deviations and (2) ungraviton corrections. As a special result in the noncommutative case, we find that the noncommutative character of the manifold would be equivalent to the temperature of a thermodynamic system. Therefore, in analogy to the zero temperature configuration, the description of spacetime in terms of a differential manifold could be obtained only asymptotically. Finally, we extend the Verlinde's derivation to a general case, which includes all possible effects, noncommutativity, ungravity, asymptotically safe gravity, electrostatic energy, and extra dimensions, showing that the procedure is solid versus such modifications.
Exercise in artificial gravity
Edmonds, Jessica Leigh
2005-01-01T23:59:59.000Z
Artificial gravity provided by short radius centrifugation is considered a promising countermeasure to the deleterious physiological effects of microgravity during long-duration space flight. We investigated the feasibility ...
Time Gravity and Quantum Mechanics
W. G. Unruh
1993-12-17T23:59:59.000Z
Time plays different roles in quantum mechanics and gravity. These roles are examined and the problems that the conflict in the roles presents for quantum gravity are briefly summarised.
Polchinski, Joseph [Kavli Institute for Theoretical Physics
2010-09-01T23:59:59.000Z
Gauge theories, which describe the particle interactions, are well understood, while quantum gravity leads to many puzzles. Remarkably, in recent years we have learned that these are actually dual, the same system written in different variables. On the one hand, this provides our most precise description of quantum gravity, resolves some long-standing paradoxes, and points to new principles. On the other, it gives a new perspective on strong interactions, with surprising connections to other areas of physics. I describe these ideas, and discuss current and future directions.
Introduction Basics of gravity theory
Visser, Matt
Introduction Basics of gravity theory Actions and Field Equations Phenomenology Discussion;Introduction Basics of gravity theory Actions and Field Equations Phenomenology Discussion and Conclusions Victoria U of Wellington - Feb 2nd 2009 #12;Introduction Basics of gravity theory Actions and Field
Massive gravity as a limit of bimetric gravity
Martin-Moruno, Prado; Visser, Matt
2013-01-01T23:59:59.000Z
Massive gravity may be viewed as a suitable limit of bimetric gravity. The limiting procedure can lead to an interesting interplay between the "background" and "foreground" metrics in a cosmological context. The fact that in bimetric theories one always has two sets of metric equations of motion continues to have an effect even in the massive gravity limit. Thus, solutions of bimetric gravity in the limit of vanishing kinetic term are also solutions of massive gravity, but the contrary statement is not necessarily true.
Gravity on Conformal Superspace
Bryan Kelleher
2003-11-11T23:59:59.000Z
The configuration space of general relativity is superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms. However, it has been argued that the configuration space for gravity should be conformal superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms and conformal transformations. Taking this conformal nature seriously leads to a new theory of gravity which although very similar to general relativity has some very different features particularly in cosmology and quantisation. It should reproduce the standard tests of general relativity. The cosmology is studied in some detail. The theory is incredibly restrictive and as a result admits an extremely limited number of possible solutions. The problems of the standard cosmology are addressed and most remarkably the cosmological constant problem is resolved in a natural way. The theory also has several attractive features with regard to quantisation particularly regarding the problem of time.
Iver Brevik
2012-11-23T23:59:59.000Z
A bulk viscosity is introduced in the formalism of modified gravity. It is shown that, on the basis of a natural scaling law for the viscosity, a simple solution can be found for quantities such as the Hubble parameter and the energy density. These solutions may incorporate a viscosity-induced Big Rip singularity. By introducing a phase transition in the cosmic fluid, the future singularity can nevertheless in principle be avoided.
Lie algebraic noncommutative gravity
Banerjee, Rabin; Samanta, Saurav [S. N. Bose National Centre for Basic Sciences, JD Block, Sector III, Salt Lake, Kolkata-700098 (India); Mukherjee, Pradip [Presidency College, 86/1 College Street, Kolkata-700073, West-Bengal (India)
2007-06-15T23:59:59.000Z
We exploit the Seiberg-Witten map technique to formulate the theory of gravity defined on a Lie algebraic noncommutative space-time. Detailed expressions of the Seiberg-Witten maps for the gauge parameters, gauge potentials, and the field strengths have been worked out. Our results demonstrate that notwithstanding the introduction of more general noncommutative structure there is no first order correction, exactly as happens for a canonical (i.e. constant) noncommutativity.
Gravity, Dimension, Equilibrium, & Thermodynamics
Jerome Perez
2006-03-30T23:59:59.000Z
Is it actually possible to interpret gravitation as space's property in a pure classical way. Then, we note that extended self-gravitating system equilibrium depends directly on the number of dimension of the space in which it evolves. Given those precisions, we review the principal thermodynamical knowledge in the context of classical gravity with arbitrary dimension of space. Stability analyses for bounded 3D systems, namely the Antonov instability paradigm, are then rapproched to some amazing properties of globular clusters and galaxies.
Koyama, Kazuya
2015-01-01T23:59:59.000Z
Einstein's theory of General Relativity (GR) is tested accurately within the local universe i.e., the Solar System, but this leaves open the possibility that it is not a good description at the largest scales in the Universe. The standard model of cosmology assumes GR as the theory to describe gravity on all scales. In 1998, astronomers made the surprising discovery that the expansion of the Universe is accelerating, not slowing down. This late-time acceleration of the Universe has become the most challenging problem in theoretical physics. Within the framework of GR, the acceleration would originate from an unknown dark energy. Alternatively, it could be that there is no dark energy and GR itself is in error on cosmological scales. The standard model of cosmology is based on a huge extrapolation of our limited knowledge of gravity. This discovery of the late time acceleration of the Universe may require us to revise the theory of gravity and the standard model of cosmology based on GR. We will review recent ...
Broader source: Energy.gov [DOE]
Commissioning specifications outline basic requirements of the commissioning process and detail the roles and responsibilities of each party involved. System checklists, startup requirements, and...
Lifshitz Gravity for Lifshitz Holography
Tom Griffin; Petr Horava; Charles M. Melby-Thompson
2012-11-20T23:59:59.000Z
We argue that Horava-Lifshitz (HL) gravity provides the minimal holographic dual for Lifshitz-type field theories with anisotropic scaling and dynamical exponent z. First we show that Lifshitz spacetimes are vacuum solutions of HL gravity, without need for additional matter. Then we perform holographic renormalization of HL gravity, and show how it reproduces the full structure of the z=2 anisotropic Weyl anomaly in dual field theories in 2+1 dimensions, while its minimal relativistic gravity counterpart yields only one of two independent central charges in the anomaly.
Abelian-Higgs strings in Rastall gravity
Eugenio R. Bezerra de Mello; Julio C. Fabris; Betti Hartmann
2015-04-02T23:59:59.000Z
In this paper we analyze Abelian-Higgs strings in a phenomenological model that takes quantum effects in curved space-time into account. This model, first introduced by Rastall, cannot be derived from an action principle. We formulate phenomenological equations of motion under the guiding principle of minimal possible deformation of the standard equations. We construct string solutions that asymptote to a flat space-time with a deficit angle by solving the set of coupled non-linear ordinary differential equations numerically. Decreasing the Rastall parameter from its Einstein gravity value we find that the deficit angle of the space-time increases and becomes equal to $2\\pi$ at some critical value of this parameter that depends on the remaining couplings in the model. For smaller values the resulting solutions are supermassive string solutions possessing a singularity at a finite distance from the string core. Assuming the Higgs boson mass to be on the order of the gauge boson mass we find that also in Rastall gravity this happens only when the symmetry breaking scale is on the order of the Planck mass. We also observe that for specific values of the parameters in the model the energy per unit length becomes proportional to the winding number, i.e. the degree of the map $S^1 \\rightarrow S^1$. Unlike in the BPS limit in Einstein gravity, this is, however, not connect to an underlying mathematical structure, but rather constitutes a would-be-BPS bound.
Ning Wu
2005-10-01T23:59:59.000Z
It is well-known that energy-momentum is the source of gravitational field. For a long time, it is generally believed that only stars with huge masses can generate strong gravitational field. Based on the unified theory of gravitational interactions and electromagnetic interactions, a new mechanism of the generation of gravitational field is studied. According to this mechanism, in some special conditions, electromagnetic energy can be directly converted into gravitational energy, and strong gravitational field can be generated without massive stars. Gravity impulse found in experiments is generated by this mechanism.
Lubricated viscous gravity currents
Kowal, Katarzyna N.; Worster, M. Grae
2015-02-10T23:59:59.000Z
. The only previous work on two-layer gravity currents (Woods & Mason 2000) involved flow in a porous medium and so did not feature viscous coupling between the layers. We have performed a series of laboratory experiments using golden syrup lubricated... and velocity are related linearly by ui ? h µl ?i. (2.20) This is a sliding law in which the sliding coefficient depends on the lower film thickness. It has a similar structure to the sliding law ? = Cu1/n used in many glaciological stud- ies (Weertman 1957...
K. H. Mariwalla
2002-05-28T23:59:59.000Z
Basis and limitations of singularity theorems for Gravity are examined. As singularity is a critical situation in course of time, study of time paths, in full generality of Equivalence principle, provides two mechanisms to prevent singularity. Resolution of singular Time translation generators into space of its orbits, and essential higher dimensions for Relativistic particle interactions has facets to resolve any real singularity problem. Conceptually, these varied viewpoints have a common denominator: arbitrariness in the definition of `energy' intrinsic to the space of operation in each case, so as to render absence of singularity a tautology for self-consistency of the systems.
Particlelike distributions of the Higgs field nonminimally coupled to gravity
Andre Fuzfa; Massimiliano Rinaldi; Sandrine Schlogel
2013-09-10T23:59:59.000Z
When the Higgs field is nonminimally coupled to gravity, there exists a family of spherically symmetric particlelike solutions to the field equations. These monopoles are the only globally regular and asymptotically flat distributions with finite energy of the Higgs field around compact objects. Moreover, spontaneous scalarization is strongly amplified for specific values of their mass and compactness.
Entirely passive heat pipe apparatus capable of operating against gravity
Koenig, Daniel R. (Santa Fe, NM)
1982-01-01T23:59:59.000Z
The disclosure is directed to an entirely passive heat pipe apparatus capable of operating against gravity for vertical distances in the order of 3 to 7 meters and more. A return conduit into which an inert gas is introduced is used to lower the specific density of the working fluid so that it may be returned a greater vertical distance from condenser to evaporator.
Reduced models for quantum gravity
T. Thiemann
1999-10-04T23:59:59.000Z
The preceding talks given at this conference have dealt mainly with general ideas for, main problems of and techniques for the task of quantizing gravity canonically. Since one of the major motivations to arrange for this meeting was that it should serve as a beginner's introduction to canonical quantum gravity, we regard it as important to demonstrate the usefulness of the formalism by means of applying it to simplified models of quantum gravity, here formulated in terms of Ashtekar's new variables. From the various, completely solvable, models that have been discussed in the literature we choose those that we consider as most suitable for our pedagogical reasons, namely 2+1 gravity and the spherically symmetric model. The former model arises from a dimensional, the latter from a Killing reduction of full 3+1 gravity. While 2+1 gravity is usually treated in terms of closed topologies without boundary of the initial data hypersurface, the toplogy for the spherically symmetric system is chosen to be asymptotically flat. Finally, 2+1 gravity is more suitably quantized using the loop representation while spherically symmetric gravity is easier to quantize via the self-dual representation. Accordingly, both types of reductions, both types of topologies and both types of representations that are mainly employed in the literature in the context of the new variables come into practice. What makes the discussion especially clear is the fact that for both models the reduced phase space turns out to be finitely dimensional.
AdS Chern-Simons Gravity induces Conformal Gravity
Rodrigo Aros; Danilo E. Diaz
2013-12-25T23:59:59.000Z
The leitmotif of this paper is the question of whether four- and higher even-dimensional Conformal Gravities do have a Chern-Simons pedigree. We show that Weyl gravity can be obtained as dimensional reduction of a five-dimensional Chern-Simons action for a suitable (gauged-fixed, tractor-like) five-dimensional AdS connection. The gauge-fixing and dimensional reduction program admits a readily generalization to higher dimensions for the case of certain conformal gravities obtained by contractions of the Weyl tensor.
Natural Inflation and Quantum Gravity
Anton de la Fuente; Prashant Saraswat; Raman Sundrum
2015-01-29T23:59:59.000Z
Cosmic Inflation provides an attractive framework for understanding the early universe and the cosmic microwave background. It can readily involve energies close to the scale at which Quantum Gravity effects become important. General considerations of black hole quantum mechanics suggest nontrivial constraints on any effective field theory model of inflation that emerges as a low-energy limit of quantum gravity, in particular the constraint of the Weak Gravity Conjecture. We show that higher-dimensional gauge and gravitational dynamics can elegantly satisfy these constraints and lead to a viable, theoretically-controlled and predictive class of Natural Inflation models.
Riding Gravity Away from Doomsday
Ashoke Sen
2015-03-27T23:59:59.000Z
The discovery that most of the energy density in the universe is stored in the form of dark energy has profound consequences for our future. In particular our current limited understanding of quantum theory of gravity indicates that some time in the future our universe will undergo a phase transition that will destroy us and everything else around us instantaneously. However the laws of gravity also suggest a way out -- some of our descendants could survive this catastrophe by riding gravity away from the danger. In this essay I describe the tale of this escape from doomsday.
Riding Gravity Away from Doomsday
Sen, Ashoke
2015-01-01T23:59:59.000Z
The discovery that most of the energy density in the universe is stored in the form of dark energy has profound consequences for our future. In particular our current limited understanding of quantum theory of gravity indicates that some time in the future our universe will undergo a phase transition that will destroy us and everything else around us instantaneously. However the laws of gravity also suggest a way out -- some of our descendants could survive this catastrophe by riding gravity away from the danger. In this essay I describe the tale of this escape from doomsday.
Compensational Gravity Fundamentals and an Application: The Cycling Universe
Vladimir S. Mashkevich
2010-04-16T23:59:59.000Z
Compensational gravity, which is regarded as a fundamental theory, is an advanced version of semiclassical gravity. It is a construction which extends the Einstein equation. Along with the energy-momentum tensor, the extended Einstein equation includes the compensation tensor, or compenson. The latter compensates for the energy-momentum tensor insufficiency, which consists in the discontinuity in time (due to quantum state reduction) and in space (due to sharp cutoff), as well as in an anomaly (nonrealistic state equation and nonzero divergence). The compenson is a primary object, for which equations are formulated. Specifically, purely dark objects may or may not exist. The dynamics of compensational gravity gives rise naturally to the cosmological constant, or dark energy and to dark matter: The compenson versus particle dark matter. On the basis of the dynamics, a cycling model of the closed universe is constructed.
Gravity as an Entropic Phenomenon
Abhiram Chivukula
2010-11-19T23:59:59.000Z
The unification of gravity with the three other forces has been an important goal of physics for some time now, because a quantum theory of gravity is necessary to explain the universe at its earliest moments. Its pursuit has largely assumed gravity's independent existence, but E. Verlinde proposed that gravity is not a fundamental force but a macroscopic phenomenon that emerges as a result of thermodynamic principles applied to the information of mass distributions. Under this framework we consider the roles played by quantum microstates, entanglement, information theory, the AdS/CFT Correspondence, and String Theory in general. We also ask whether Verlinde's proposal suggests that action principles should be thermodynamic in nature.
Gravity as an Entropic Phenomenon
Chivukula, Abhiram
2010-01-01T23:59:59.000Z
The unification of gravity with the three other forces has been an important goal of physics for some time now, because a quantum theory of gravity is necessary to explain the universe at its earliest moments. Its pursuit has largely assumed gravity's independent existence, but E. Verlinde proposed that gravity is not a fundamental force but a macroscopic phenomenon that emerges as a result of thermodynamic principles applied to the information of mass distributions. Under this framework we consider the roles played by quantum microstates, entanglement, information theory, the AdS/CFT Correspondence, and String Theory in general. We also ask whether Verlinde's proposal suggests that action principles should be thermodynamic in nature.
Testing Gravity Theories Using Stars
Jeremy Sakstein; Bhuvnesh Jain; Vinu Vikram
2014-09-12T23:59:59.000Z
Modified theories of gravity have received a renewed interest due to their ability to account for the cosmic acceleration. In order to satisfy the solar system tests of gravity, these theories need to include a screening mechanism that hides the modifications on small scales. One popular and well-studied theory is chameleon gravity. Our own galaxy is necessarily screened, but less dense dwarf galaxies may be unscreened and their constituent stars can exhibit novel features. In particular, unscreened stars are brighter, hotter and more ephemeral than screened stars in our own galaxy. They also pulsate with a shorter period. In this essay, we exploit these new features to constrain chameleon gravity to levels three orders of magnitude lower the previous measurements. These constraints are currently the strongest in the literature.
Critical Gravity in Four Dimensions
Lue, H. [China Economics and Management Academy, Central University of Finance and Economics, Beijing 100081 (China); Institute for Advanced Study, Shenzhen University, Nanhai Avenue 3688, Shenzhen 518060 (China); Pope, C. N. [George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States); DAMTP, Centre for Mathematical Sciences, Cambridge University, Wilberforce Road, Cambridge CB3 OWA (United Kingdom)
2011-05-06T23:59:59.000Z
We study four-dimensional gravity theories that are rendered renormalizable by the inclusion of curvature-squared terms to the usual Einstein action with a cosmological constant. By choosing the parameters appropriately, the massive scalar mode can be eliminated and the massive spin-2 mode can become massless. This ''critical'' theory may be viewed as a four-dimensional analogue of chiral topologically massive gravity, or of critical 'new massive gravity' with a cosmological constant, in three dimensions. We find that the on-shell energy for the remaining massless gravitons vanishes. There are also logarithmic spin-2 modes, which have positive energy. The mass and entropy of standard Schwarzschild-type black holes vanish. The critical theory might provide a consistent toy model for quantum gravity in four dimensions.
Quantum Gravity: Motivations and Alternatives
Reiner Hedrich
2009-08-03T23:59:59.000Z
The mutual conceptual incompatibility between GR and QM/QFT is generally seen as the most essential motivation for the development of a theory of Quantum Gravity (QG). It leads to the insight that, if gravity is a fundamental interaction and QM is universally valid, the gravitational field will have to be quantized, not at least because of the inconsistency of semi-classical theories of gravity. If this means to quantize GR, its identification of the gravitational field with the spacetime metric has to be taken into account. And the resulting quantum theory has to be background-independent. This can not be achieved by means of quantum field theoretical procedures. More sophisticated strategies have to be applied. One of the basic requirements for such a quantization strategy is that the resulting quantum theory has GR as a classical limit. - However, should gravity not be a fundamental, but an residual, emergent interaction, it could very well be an intrinsically classical phenomenon. Should QM be nonetheless universally valid, we had to assume a quantum substrate from which gravity would result as an emergent classical phenomenon. And there would be no conflict with the arguments against semi-classical theories, because there would be no gravity at all on the substrate level. The gravitational field would not have any quantum properties, and a quantization of GR would not lead to any fundamental theory. The objective of a theory of 'QG' would instead be the identification of the quantum substrate from which gravity results. - The paper tries to give an overview over the main options for theory construction in the field of QG. Because of the still unclear status of gravity and spacetime, it pleads for the necessity of a plurality of conceptually different approaches to QG.
D. Fargion
2005-11-23T23:59:59.000Z
The present gravitational wave detectors are reaching lowest metric deviation fields able to detect galactic and extra-galactic gravitational waves, related to Supernova explosions up to Virgo cluster. The same gravitational wave detector are nevertheless almost able to reveal, in principle, near field Newtonian gravitational perturbations due to fast huge mass displacements as the ones occurring during largest Earth-Quake or Tsunami as the last on 26nd December 2004 in Asiatic area. Virgo and Ligo detector are unfortunately recording on high frequencies (above tens Hz) while the signal of the Tsunami lay at much lower range (below 0.1 Hz). Nevertheless prompt gravitational near field deformation by the Tsunami might reach the future LISA threshold sensitivity and frequency windows if such an array is located nearby (3000-10000) km distances. Unfortunately the present LISA system should be located at Lagrange point too far (1.5 million km. far away). We note however that the later continental mass rearrangement and their gravitational field assessment on Earth must induce, for Richter Magnitude 9-like Tsunami, a different terrestrial inertia momentum and a different principal rotation axis. In conclusion we remind that gravitational geodetic deviation on new precise satellites (GOCE 2006), assisted by GPS network, might nevertheless reach in the near future the needed threshold and accuracy to reveal Tsunami by their prompt tidal gravity field deviations . An array of such geoid detector maybe correlated with LISA-like satellite on Earth orbits may offer the fastest alarm system.
Spherically symmetric conformal gravity and "gravitational bubbles"
V. A. Berezin; V. I. Dokuchaev; Yu. N. Eroshenko
2014-12-09T23:59:59.000Z
The general structure of the spherically symmetric solutions in the Weyl conformal gravity is described. The corresponding Bach equation are derived for the special type of metrics, which can be considered as the representative of the general class. The complete set of the pure vacuum solutions is found. It consists of two classes. The first one contains the solutions with constant two-dimensional curvature scalar of our specific metrics, and the representatives are the famous Robertson-Walker metrics. One of them we called the "gravitational bubbles", which is compact and with zero Weyl tensor. The second class is more general, with varying curvature scalar. We found its representative as the one-parameter family. It appears that it can be conformally covered by the thee-parameter Mannheim-Kazanas solution. We also investigated the general structure of the energy-momentum tensor in the spherical conformal gravity and constructed the vectorial equation that reveals clearly the same features of non-vacuum solutions. One of them, the metrics a la Vaidya, is explicitly written.
Conformal Lifshitz Gravity from Holography
Tom Griffin; Petr Horava; Charles M. Melby-Thompson
2012-04-03T23:59:59.000Z
We show that holographic renormalization of relativistic gravity in asymptotically Lifshitz spacetimes naturally reproduces the structure of gravity with anisotropic scaling: The holographic counterterms induced near anisotropic infinity take the form of the action for gravity at a Lifshitz point, with the appropriate value of the dynamical critical exponent $z$. In the particular case of 3+1 bulk dimensions and $z=2$ asymptotic scaling near infinity, we find a logarithmic counterterm, related to anisotropic Weyl anomaly of the dual CFT, and show that this counterterm reproduces precisely the action of conformal gravity at a $z=2$ Lifshitz point in 2+1 dimensions, which enjoys anisotropic local Weyl invariance and satisfies the detailed balance condition. We explain how the detailed balance is a consequence of relations among holographic counterterms, and point out that a similar relation holds in the relativistic case of holography in $AdS_5$. Upon analytic continuation, analogous to the relativistic case studied recently by Maldacena, the action of conformal gravity at the $z=2$ Lifshitz point features in the ground-state wavefunction of a gravitational system with an interesting type of spatial anisotropy.
Dust Static Spherically Symmetric Solution in $f(R)$ Gravity
Muhammad Sharif; Hafiza Rizwana Kausar
2011-02-21T23:59:59.000Z
In this paper, we take dust matter and investigate static spherically symmetric solution of the field equations in metric f(R) gravity. The solution is found with constant Ricci scalar curvature and its energy distribution is evaluated by using Landau-Lifshitz energy-momentum complex. We also discuss the stability condition and constant scalar curvature condition for some specific popular choices of f(R) models in addition to their energy distribution.
Gauge Theory of Quantum Gravity
J. W. Moffat
1994-01-04T23:59:59.000Z
A gauge theory of quantum gravity is formulated, in which an internal, field dependent metric is introduced which non-linearly realizes the gauge fields on the non-compact group $SL(2,C)$, while linearly realizing them on $SU(2)$. Einstein's $SL(2,C)$ invariant theory of gravity emerges at low energies, since the extra degrees of freedom associated with the quadratic curvature and the internal metric only dominate at high energies. In a fixed internal metric gauge, only the the $SU(2)$ gauge symmetry is satisfied, the particle spectrum is identified and the Hamiltonian is shown to be bounded from below. Although Lorentz invariance is broken in this gauge, it is satisfied in general. The theory is quantized in this fixed, broken symmetry gauge as an $SU(2)$ gauge theory on a lattice with a lattice spacing equal to the Planck length. This produces a unitary and finite theory of quantum gravity.
Tian, David Wenjie
2015-01-01T23:59:59.000Z
According to Lovelock's theorem, the Hilbert-Einstein and the Lovelock actions are indistinguishable from their field equations. However, they have different scalar-tensor counterparts, which correspond to the Brans-Dicke and the \\emph{Lovelock-Brans-Dicke} (LBD) gravities, respectively. In this paper the LBD model of alternative gravity with the Lagrangian density $\\mathscr{L}_{\\text{LBD}}=\\frac{1}{16\\pi}\\left[\\phi\\left(R+\\frac{a}{\\sqrt{-g}}{}^*RR + b\\mathcal{G}\\right)-\\frac{\\omega_{\\text L}}{\\phi}\
de Sitter gravity/Euclidean conformal gravity correspondence
Chatterjee, Atreya
2015-01-01T23:59:59.000Z
The holographic dual of a gravitational theory around the de Sitter background is argued to be a Euclidean conformal gravity theory in one fewer dimensions. The measure for the holographic theory naturally includes a sum over topologies as well as conformal structures.
Emergent 4D Gravity from Matrix Models
Harold Steinacker
2007-12-19T23:59:59.000Z
Recent progress in the understanding of gravity on noncommutative spaces is discussed. A gravity theory naturally emerges from matrix models of noncommutative gauge theory. The effective metric depends on the dynamical Poisson structure, absorbing the degrees of freedom of the would-be U(1) gauge field. The gravity action is induced upon quantization.
Intrusive gravity currents in two-layer
Flynn, Morris R.
Intrusive gravity currents in two-layer stratified media Morris R. Flynn & Paul F. Linden Dept.avalanche.org/pictures #12;· `Microbursts' pose a non-trivial threat to airplane safety Introduction Impacts on human health;· Whereas gravity currents travel along a solid boundary, intrusive gravity currents or intrusions propagate
Einstein static Universe in non-minimal kinetic coupled gravity
K. Atazadeh; F. Darabi
2015-04-18T23:59:59.000Z
We study the stability of Einstein static Universe, with FLRW metric, by considering linear homogeneous perturbations in the kinetic coupled gravity. By taking linear homogeneous perturbations, we find that the stability of Einstein static Universe, in the kinetic coupled gravity with quadratic scalar field potential, for closed ($K=1$) isotropic and homogeneous FLRW Universe depends on the coupling parameters $\\kappa$ and $\\varepsilon$. Specifically, for $\\kappa=L_P^2$ and $\\varepsilon=1$ we find that the stability condition imposes the inequality $a_0>\\sqrt{3}L_P$ on the initial size $a_0$ of the closed Einstein static Universe before the inflation. Such inequality asserts that the initial size of the Einstein static Universe must be greater than the Planck length $L_P$, in consistency with the quantum gravity and quantum cosmology requirements. In this way, we have determined the non-minimal coupling parameter $\\kappa$ in the context of Einstein static Universe. Such a very small parameter is favored in the inflationary models constructed in the kinetic coupled gravity. We have also studied the stability against the vector and tensor perturbations and discussed on the acceptable values of the equation of state parameter.
Testing gravity on kiloparsec scales with strong gravitational lenses
Tristan L. Smith
2010-04-12T23:59:59.000Z
Modifications to GR generically predict time and scale-dependent effects which may be probed by observations of strong lensing by galaxies. Measurements of the stellar velocity dispersion determine the dynamical mass whereas measurements of the Einstein radius determine the lensing mass. In GR these two masses are equal; in alternative gravity theories they may not be. Using measurements of the stellar velocity dispersion and strong lensing around galaxies from the Sloan Lens ACS (SLACS) survey we place constraints on lensing in modified gravity theories and extend previous studies by applying this data to explore its dependence on various properties of the lens such as the lens redshift or mass and thereby constrain scalar-tensor, f(R) gravity theories, and generic parameterizations of deviations from GR. Besides applying the observations to these specific gravity theories, the data places a constraint on a generic dependence of modifications to GR on the lens mass and redshift. At the 68% confidence level we find that the ratio between the lensing and dynamical masses can only vary by less then 50% over a mass range for the lens galaxies of 1E12 < M/Msun < 1E14 and less than 40% over the redshift range 0.06 < z < 0.36.
Cosmological Hints of Modified Gravity ?
Eleonora Di Valentino; Alessandro Melchiorri; Joseph Silk
2015-09-24T23:59:59.000Z
The recent measurements of Cosmic Microwave Background temperature and polarization anisotropies made by the Planck satellite have provided impressive confirmation of the $\\Lambda$CDM cosmological model. However interesting hints of slight deviations from $\\Lambda$CDM have been found, including a $95 \\%$ c.l. preference for a "modified gravity" structure formation scenario. In this paper we confirm the preference for a modified gravity scenario from Planck 2015 data, find that modified gravity solves the so-called $A_{lens}$ anomaly in the CMB angular spectrum, and constrains the amplitude of matter density fluctuations to $\\sigma_8=0.815_{-0.048}^{+0.032}$, in better agreement with weak lensing constraints. Moreover, we find a lower value for the reionization optical depth of $\\tau=0.059\\pm0.020$ (to be compared with the value of $\\tau= 0.079 \\pm 0.017$ obtained in the standard scenario), more consistent with recent optical and UV data. We check the stability of this result by considering possible degeneracies with other parameters, including the neutrino effective number, the running of the spectral index and the amount of primordial helium. The indication for modified gravity is still present at about $95\\%$ c.l., and could become more significant if lower values of $\\tau$ were to be further confirmed by future cosmological and astrophysical data.
Liouville quantum gravity and KPZ
Duplantier, Bertrand
Consider a bounded planar domain D, an instance h of the Gaussian free field on D, with Dirichlet energy ... and a constant 0[less than or equal to]?<2. The Liouville quantum gravity measure on D is the weak limit as ...
Thomas Rauch
2006-07-11T23:59:59.000Z
NLTE spectral analyses of high-gravity central stars by means of state-of-the-art model atmosphere techniques provide information about the precursor AGB stars. The hydrogen-deficient post-AGB stars allow investigations on the intershell matter which is apparently exhibited at the stellar surface. We summarize recent results from imaging, spectroscopy, and spectropolarimetry.
Goedel-type universes in Palatini f(R) gravity
Santos, J.; Oliveira, T. B. R. F. [Universidade Federal do Rio Grande do Norte, Departamento de Fisica, 59072-970 Natal-RN (Brazil); Reboucas, M. J. [Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro-RJ (Brazil)
2010-06-15T23:59:59.000Z
We examine the question as to whether the Palatini f(R) gravity theories permit space-times in which the causality is violated. We show that every perfect-fluid Goedel-type solution of Palatini f(R) gravity with density {rho} and pressure p that satisfy the weak energy condition {rho}+p{>=}0 is necessarily isometric to the Goedel geometry, demonstrating therefore that these theories present causal anomalies in the form of closed timelike curves. This result extends a theorem on Goedel-type models to the framework of Palatini f(R) gravity theory. We concretely examine the Goedel-type perfect-fluid solutions in specific f(R)=R-{alpha}/R{sup n} Palatini gravity theory, where the free parameters {alpha} and n have been recently constrained by observational data. We show that for positive matter density and for {alpha} and n within the interval permitted by the observations, this theory does not admit the Goedel geometry as a perfect-fluid solution of its field equations. In this sense, this theory remedies the causal pathology in the form of closed timelike curves which is allowed in general relativity. We derive an expression for a critical radius r{sub c} (beyond which the causality is violated) for an arbitrary Palatini f(R) theory. The expression makes apparent that the violation of causality depends on the form of f(R) and on the matter content components. We also examine the violation of causality of Goedel-type by considering a single scalar field as the matter content. For this source we show that Palatini f(R) gravity gives rise to a unique Goedel-type solution with no violation of causality.
Introduction to Modified Gravity and Gravitational Alternative for Dark Energy
Nojiri, S
2006-01-01T23:59:59.000Z
We review various modified gravities considered as gravitational alternative for dark energy. Specifically, we consider the versions of $f(R)$, $f(G)$ or $f(R,G)$ gravity, model with non-linear gravitational coupling or string-inspired model with Gauss-Bonnet-dilaton coupling in the late universe where they lead to cosmic speed-up. It is shown that some of such theories may pass the Solar System tests. On the same time, it is demonstrated that they have quite rich cosmological structure: they may naturally describe the effective (cosmological constant, quintessence or phantom) late-time era with a possible transition from decceleration to acceleration thanks to gravitational terms which increase with scalar curvature decrease. The possibility to explain the coincidence problem as the manifestation of the universe expansion in such models is mentioned. The late (phantom or quintessence) universe filled with dark fluid with inhomogeneous equation of state (where inhomogeneous terms are originated from the modif...
Signature change events: A challenge for quantum gravity?
White, Angela; Visser, Matt
2008-01-01T23:59:59.000Z
Within the framework of either Euclidian (functional-integral) quantum gravity or canonical general relativity the signature of the manifold is a priori unconstrained. Furthermore, recent developments in the emergent spacetime programme have led to a physically feasible implementation of signature change events. This suggests that it is time to revisit the sometimes controversial topic of signature change in general relativity. Specifically, we shall focus on the behaviour of a quantum field subjected to a manifold containing regions of different signature. We emphasise that, regardless of the underlying classical theory, there are severe problems associated with any quantum field theory residing on a signature-changing background. (Such as the production of what is naively an infinite number of particles, with an infinite energy density.) From the viewpoint of quantum gravity phenomenology, we discuss possible consequences of an effective Lorentz symmetry breaking scale. To more fully understand the physics ...
New Branches of Massive Gravity
Comelli, Denis; Koyama, Kazuya; Pilo, Luigi; Tasinato, Gianmassimo
2015-01-01T23:59:59.000Z
The basic building block for Lorentz invariant and ghost free massive gravity is the square root of the combination $g^{-1}\\eta\\,$, where $g^{-1}$ is the inverse of the physical metric and $\\eta$ is a reference metric. Since the square root of a matrix is not uniquely defined, it is possible to have physically inequivalent potentials corresponding to different branches. We show that around Minkowski background the only perturbatively well defined branch is the potential proposed by de Rham, Gabadadze and Tolley. On the other hand, if Lorentz symmetry is broken spontaneously, other potentials exist with a standard perturbative expansion. We show this explicitly building new Lorentz invariant, ghost-free massive gravity potentials for theories that in the background preserve rotational invariance, but break Lorentz boosts.
Hybrid metric-Palatini gravity
Capozziello, Salvatore; Koivisto, Tomi S; Lobo, Francisco S N; Olmo, Gonzalo J
2015-01-01T23:59:59.000Z
Recently, the phenomenology of f(R) gravity has been scrutinized motivated by the possibility to account for the self-accelerated cosmic expansion without invoking dark energy sources. Besides, this kind of modified gravity is capable of addressing the dynamics of several self-gravitating systems alternatively to the presence of dark matter. It has been established that both metric and Palatini versions of these theories have interesting features but also manifest severe and different downsides. A hybrid combination of theories, containing elements from both these two formalisms, turns out to be also very successful accounting for the observed phenomenology and is able to avoid some drawbacks of the original approaches. This article reviews the formulation of this hybrid metric-Palatini approach and its main achievements in passing the local tests and in applications to astrophysical and cosmological scenarios, where it provides a unified approach to the problems of dark energy and dark matter.
Quantum gravity without Lorentz invariance
Sotiriou, Thomas P; Weinfurtner, Silke
2009-01-01T23:59:59.000Z
There has been a significant surge of interest in Horava's model for 3+1 dimensional quantum gravity, this model being based on anisotropic scaling at a z=3 Lifshitz point. Horava's model, and its variants, show dramatically improved ultra-violet behaviour at the cost of exhibiting violation of Lorentz invariance at ultra-high momenta. Following up on our earlier note, [arXiv:0904.4464 [hep-th
Cosmological Hints of Modified Gravity ?
Di Valentino, Eleonora; Silk, Joseph
2015-01-01T23:59:59.000Z
The recent measurements of Cosmic Microwave Background temperature and polarization anisotropies made by the Planck satellite have provided impressive confirmation of the $\\Lambda$CDM cosmological model. However interesting hints of slight deviations from $\\Lambda$CDM have been found, including a $95 \\%$ c.l. preference for a "modified gravity" structure formation scenario. In this paper we confirm the preference for a modified gravity scenario from Planck 2015 data, find that modified gravity solves the so-called $A_{lens}$ anomaly in the CMB angular spectrum, and constrains the amplitude of matter density fluctuations to $\\sigma_8=0.815_{-0.048}^{+0.032}$, in better agreement with weak lensing constraints. Moreover, we find a lower value for the reionization optical depth of $\\tau=0.059\\pm0.020$ (to be compared with the value of $\\tau= 0.079 \\pm 0.017$ obtained in the standard scenario), more consistent with recent optical and UV data. We check the stability of this result by considering possible degeneraci...
Supersymmetry and Gravity in Noncommutative Field Theories
Victor O. Rivelles
2003-05-14T23:59:59.000Z
We discuss the renormalization properties of noncommutative supersymmetric theories. We also discuss how the gauge field plays a role similar to gravity in noncommutative theories.
Heating System Specification Specification of Heating System
Day, Nancy
Appendix A Heating System Specification /* Specification of Heating System (loosely based */ requestHeat : Room ? bool; 306 #12; APPENDIX A. HEATING SYSTEM SPECIFICATION 307 /* user inputs */ livingPattern : Room ? behaviour; setTemp : Room ? num; heatSwitchOn, heatSwitchOff, userReset : simple
Introduction to Modified Gravity and Gravitational Alternative for Dark Energy
S. Nojiri; S. D. Odintsov
2006-03-31T23:59:59.000Z
We review various modified gravities considered as gravitational alternative for dark energy. Specifically, we consider the versions of $f(R)$, $f(G)$ or $f(R,G)$ gravity, model with non-linear gravitational coupling or string-inspired model with Gauss-Bonnet-dilaton coupling in the late universe where they lead to cosmic speed-up. It is shown that some of such theories may pass the Solar System tests. On the same time, it is demonstrated that they have quite rich cosmological structure: they may naturally describe the effective (cosmological constant, quintessence or phantom) late-time era with a possible transition from decceleration to acceleration thanks to gravitational terms which increase with scalar curvature decrease. The possibility to explain the coincidence problem as the manifestation of the universe expansion in such models is mentioned. The late (phantom or quintessence) universe filled with dark fluid with inhomogeneous equation of state (where inhomogeneous terms are originated from the modified gravity) is also described.
Gravity Techniques | Open Energy Information
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on DeliciousPlasmaP a g eWorks -09-0018-CX Jump to:DasaValleyEnergy InformationGranville Baird JumpGravity Techniques
Entirely passive heat-pipe apparatus capable of operating against gravity
Koenig, D.R.
1981-02-11T23:59:59.000Z
The disclosure is directed to an entirely passive heat pipe apparatus capable of operating against gravity for vertical distances in the order of 3 to 7 and more. A return conduit into which an inert gas is introduced is used to lower the specific density of the working fluid so that it may be returned a greater vertical distance from condenser to evaporator.
The local potential approximation in quantum gravity
Dario Benedetti; Francesco Caravelli
2012-10-09T23:59:59.000Z
Within the context of the functional renormalization group flow of gravity, we suggest that a generic f(R) ansatz (i.e. not truncated to any specific form, polynomial or not) for the effective action plays a role analogous to the local potential approximation (LPA) in scalar field theory. In the same spirit of the LPA, we derive and study an ordinary differential equation for f(R) to be satisfied by a fixed point of the renormalization group flow. As a first step in trying to assess the existence of global solutions (i.e. true fixed point) for such equation, we investigate here the properties of its solutions by a comparison of various series expansions and numerical integrations. In particular, we study the analyticity conditions required because of the presence of fixed singularities in the equation, and we develop an expansion of the solutions for large R up to order N=29. Studying the convergence of the fixed points of the truncated solutions with respect to N, we find a characteristic pattern for the location of the fixed points in the complex plane, with one point stemming out for its stability. Finally, we establish that if a non-Gaussian fixed point exists within the full f(R) approximation, it corresponds to an R^2 theory.
Galaxy Clustering in 3D and Modified Gravity Theories
Dipak Munshi; Geraint Pratten; Patrick Valageas; Peter Coles; Philippe Brax
2015-08-03T23:59:59.000Z
We study Modified Gravity (MG) theories by modelling the redshifted matter power spectrum in a spherical Fourier-Bessel (sFB) basis. We use a fully non-linear description of the real-space matter power-spectrum and include the lowest-order redshift-space correction (Kaiser effect), taking into account some additional non-linear contributions. Ignoring relativistic corrections, which are not expected to play an important role for a shallow survey, we analyse two different modified gravity scenarios, namely the generalised Dilaton scalar-tensor theories and the $f({R})$ models in the large curvature regime. We compute the 3D power spectrum ${\\cal C}^s_{\\ell}(k_1,k_2)$ for various such MG theories with and without redshift space distortions, assuming precise knowledge of background cosmological parameters. Using an all-sky spectroscopic survey with Gaussian selection function $\\varphi(r)\\propto \\exp(-{r^2 / r^2_0})$, $r_0 = 150 \\, h^{-1} \\, {\\textrm{Mpc}}$, and number density of galaxies $\\bar {\\textrm{N}} =10^{-4}\\;{\\textrm{Mpc}}^{-3}$, we use a $\\chi^2$ analysis, and find that the lower-order $(\\ell \\leq 25)$ multipoles of ${\\cal C}^s_\\ell(k,k')$ (with radial modes restricted to $k 25$ modes can further reduce the error bars and thus in principle make cosmological gravity constraints competitive with solar system tests. However this will require an accurate modelling of non-linear redshift space distortions. Using a tomographic $\\beta(a)$-$m(a)$ parameterization we also derive constraints on specific parameters describing the Dilaton models of modified gravity.
Center for Gravity, Electrical & Magnetic Studies
Center for Gravity, Electrical & Magnetic Studies Colorado School of Mines CGEM Thesis Improving Golden, CO 80401 http://www.geophysics.mines.edu/cgem #12;Center for Gravity, Electrical & Magnetic topic stems from the recent use of multiple magnetometers, which allows for measurements of magnetic
Horava-Lifshitz gravity with detailed balance
Daniele Vernieri; Thomas P. Sotiriou
2012-12-18T23:59:59.000Z
Horava-Lifshitz gravity with "detailed balance" but without the projectability assumption is discussed. It is shown that detailed balance is quite efficient in limiting the proliferation of couplings in Horava-Lifshitz gravity, and that its implementation without the projectability assumption leads to a theory with sensible dynamics. However, the (bare) cosmological constant is restricted to be large and negative.
Reconstruction of Einstein-Aether Gravity from other Modified Gravity Models
Chayan Ranjit; Ujjal Debnath
2014-09-08T23:59:59.000Z
We briefly describe the modified Friedmann equations for Einstein-Aether gravity theory and we find the effective density and pressure. The purpose of our present work is to reconstruction of Einstein-Aether Gravity from other modified gravities like $f(T)$, $f(R)$, $f(G)$, $f(R,T)$ and $f(R,G)$ and check its viability. The scale factor is chosen in power law form. The free function $F(K)$ for Einstein-Aether gravity (where $K$ is proportional to $H^{2}$) have been found in terms for $K$ by the correspondence between Einstein-Aether gravity and other modified gravities and the nature of $F(K)$ vs $K$ have been shown graphically for every cases. Finally, we analyzed the stability of each reconstructed Einstein-Aether gravity model.
Threat Mitigation: The Gravity Tractor
Russell Schweickart; Clark Chapman; Dan Durda; Piet Hut
2006-08-15T23:59:59.000Z
The Gravity Tractor (GT) is a fully controlled asteroid deflection concept using the mutual gravity between a robotic spacecraft and an asteroid to slowly accelerate the asteroid in the direction of the "hovering" spacecraft. Based on early warning, provided by ground tracking and orbit prediction, it would be deployed a decade or more prior to a potential impact. Ion engines would be utilized for both the rendezvous with the asteroid and the towing phase. Since the GT does not dock with or otherwise physically contact the asteroid during the deflection process there is no requirement for knowledge of the asteroid's shape, composition, rotation state or other "conventional" characteristics. The GT would first reduce the uncertainty in the orbit of the asteroid via Earth tracking of its radio transponder while station keeping with the asteroid. If, after analysis of the more precise asteroid orbit a deflection is indeed indicated, the GT would "hover" above the surface of the asteroid in the direction of the required acceleration vector for a duration adequate to achieve the desired velocity change. The orbit of the asteroid is continuously monitored throughout the deflection process and the end state is known in real time. The performance envelope for the GT includes most NEOs which experience close gravitational encounters prior to impact and those below 150-200 meters in diameter on a direct Earth impact trajectory.
Solar System constraints to nonminimally coupled gravity
Orfeu Bertolami; Riccardo March; Jorge Páramos
2013-06-05T23:59:59.000Z
We extend the analysis of Chiba, Smith and Erickcek \\cite{CSE} of Solar System constraints on $f(R)$ gravity to a class of nonminimally coupled (NMC) theories of gravity. These generalize $f(R)$ theories by replacing the action functional of General Relativity (GR) with a more general form involving two functions $f^1(R)$ and $f^2(R)$ of the Ricci scalar curvature $R$. While the function $f^1(R)$ is a nonlinear term in the action, analogous to $f(R)$ gravity, the function $f^2(R)$ yields a NMC between the matter Lagrangian density $\\LL_m$ and the scalar curvature. The developed method allows for obtaining constraints on the admissible classes of functions $f^1(R)$ and $f^2(R)$, by requiring that predictions of NMC gravity are compatible with Solar System tests of gravity. We apply this method to a NMC model which accounts for the observed accelerated expansion of the Universe.
Non-Linear Massive Gravity with Additional Primary Constraint and Absence of Ghosts
J. Kluson
2012-04-13T23:59:59.000Z
We complete the Hamiltonian analysis of specific model of non-linear massive gravity that was started in arXiv:1112.5267. We identify the primary constraint and corresponding secondary constraint. We show that they are the second class constraints and hence they lead to the elimination of the additional scalar mode. We also find that the remaining constraints are the first class constraints with the structure that corresponds to the manifestly diffeomorphism invariant theory. Finally we determine the number of physical degrees of freedom and we show that it corresponds to the number of physical modes of massive gravity.
Non-AdS holography in 3-dimensional higher spin gravity - General recipe and example
H. Afshar; M. Gary; D. Grumiller; R. Rashkov; M. Riegler
2012-11-16T23:59:59.000Z
We present the general algorithm to establish the classical and quantum asymptotic symmetry algebra for non-AdS higher spin gravity and implement it for the specific example of spin-3 gravity in the non-principal embedding with Lobachevsky (H^2xR) boundary conditions. The asymptotic symmetry algebra for this example consists of a quantum W_3^2 (Polyakov-Bershadsky) and an affine u(1) algebra. We show that unitary representations of the quantum W_3^2 algebra exist only for two values of its central charge, the trivial c=0 "theory" and the simple c=1 theory.
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Specific Group Hardware Specific Group Hardware ALICE palicevo1 The Virtual Organization (VO) server. Serves as gatekeeper for ALICE jobs. It's duties include getting assignments...
Gravity-Induced Vacuum Dominance
Lima, William C. C.; Vanzella, Daniel A. T. [Instituto de Fisica de Sao Carlos, Universidade de Sao Paulo, Caixa Postal 369, CEP 15980-900, Sao Carlos, SP (Brazil)
2010-04-23T23:59:59.000Z
It has been widely believed that, except in very extreme situations, the influence of gravity on quantum fields should amount to just small, subdominant contributions. This view seemed to be endorsed by the seminal results obtained over the last decades in the context of renormalization of quantum fields in curved spacetimes. Here, however, we argue that this belief is false by showing that there exist well-behaved spacetime evolutions where the vacuum energy density of free quantum fields is forced, by the very same background spacetime, to become dominant over any classical energy-density component. By estimating the time scale for the vacuum energy density to become dominant, and therefore for backreaction on the background spacetime to become important, we argue that this (infrared) vacuum dominance may bear unexpected astrophysical and cosmological implications.
Tom Fleming; Mark Gross; Ray Renken
1994-01-04T23:59:59.000Z
We define a simplified version of Regge quantum gravity where the link lengths can take on only two possible values, both always compatible with the triangle inequalities. This is therefore equivalent to a model of Ising spins living on the links of a regular lattice with somewhat complicated, yet local interactions. The measure corresponds to the natural sum over all 2^links configurations, and numerical simulations can be efficiently implemented by means of look-up tables. In three dimensions we find a peak in the ``curvature susceptibility'' which grows with increasing system size. However, the value of the corresponding critical exponent as well as the behavior of the curvature at the transition differ from that found by Hamber and Williams for the Regge theory with continuously varying link lengths.
Emergent Horava gravity in graphene
G. E. Volovik; M. A. Zubkov
2013-07-07T23:59:59.000Z
First of all, we reconsider the tight - binding model of monolayer graphene, in which the variations of the hopping parameters are allowed. We demonstrate that the emergent 2D Weitzenbock geometry as well as the emergent U(1) gauge field appear. The emergent gauge field is equal to the linear combination of the components of the zweibein. Therefore, we actually deal with the gauge fixed version of the emergent 2+1 D teleparallel gravity. In particular, we work out the case, when the variations of the hopping parameters are due to the elastic deformations, and relate the elastic deformations with the emergent zweibein. Next, we investigate the tight - binding model with the varying intralayer hopping parameters for the multilayer graphene with the ABC stacking. In this case the emergent 2D Weitzenbock geometry and the emergent U(1) gauge field appear as well, the emergent low energy effective field theory has the anisotropic scaling.
Dimensional Reduction in Quantum Gravity
G. 't Hooft
2009-03-20T23:59:59.000Z
The requirement that physical phenomena associated with gravitational collapse should be duly reconciled with the postulates of quantum mechanics implies that at a Planckian scale our world is not 3+1 dimensional. Rather, the observable degrees of freedom can best be described as if they were Boolean variables defined on a two-dimensional lattice, evolving with time. This observation, deduced from not much more than unitarity, entropy and counting arguments, implies severe restrictions on possible models of quantum gravity. Using cellular automata as an example it is argued that this dimensional reduction implies more constraints than the freedom we have in constructing models. This is the main reason why so-far no completely consistent mathematical models of quantum black holes have been found. Essay dedicated to Abdus Salam.
Loop Quantum Gravity 1. Classical framework : Ashtekar-Barbero connection
Sart, Remi
gravity Why Quantum Gravity ? Gravitation vs. Quantum Physics : the two infinities Gravitation : large Quantum Gravity ? Gravitation vs. Quantum Physics : the two infinities Gravitation : large scales-perturbative renormalization Gravity is not a fundamental theory but it is effective (law energy) Â· it has to be modified
Ning Wu
2012-07-11T23:59:59.000Z
When we discuss problems on gravity, we can not avoid some fundamental physical problems, such as space-time, inertia, and inertial reference frame. The goal of this paper is to discuss the logic system of gravity theory and the problems of space-time, inertia, and inertial reference frame. The goal of this paper is to set up the theory on space-time in gauge theory of gravity. Based on this theory, it is possible for human kind to manipulate physical space-time on earth, and produce a machine which can physically prolong human's lifetime.
Status of Horava gravity: A personal perspective
Visser, Matt
2011-01-01T23:59:59.000Z
Horava gravity is a relatively recent (Jan 2009) idea in theoretical physics for trying to develop a quantum field theory of gravity. It is not a string theory, nor loop quantum gravity, but is instead a traditional quantum field theory that breaks Lorentz invariance at ultra-high (presumably trans-Planckian) energies, while retaining approximate Lorentz invariance at low and medium (sub-Planckian) energies. The challenge is to keep the Lorentz symmetry breaking controlled and small - small enough to be compatible with experiment. I will give a very general overview of what is going on in this field, paying particular attention to the disturbing role of the scalar graviton.
Classifying and avoiding singularities in the alternative gravity dark energy models
Capozziello, S; Nojiri, S; Odintsov, S D
2009-01-01T23:59:59.000Z
The future finite-time singularities emerging in alternative gravity dark energy models are classified and studied in Jordan and Einstein frames. It is shown that such singularity may occur even in flat spacetime for the specific choice of the effective potential. The conditions for the avoidance of finite-time singularities are presented and discussed. The problem is reduced to the study of a scalar field evolving on an effective potential by using the conformal transformations. Some viable modified gravity models are analyzed in detail and the way to cure singularity is considered by introducing the higher-order curvature corrections. These results maybe relevant for the resolution of the conjectured problem in the relativistic star formation in such modified gravity where finite-time singularity is also manifested.
Classifying and avoiding singularities in the alternative gravity dark energy models
S. Capozziello; M. De Laurentis; S. Nojiri; S. D. Odintsov
2009-06-30T23:59:59.000Z
The future finite-time singularities emerging in alternative gravity dark energy models are classified and studied in Jordan and Einstein frames. It is shown that such singularity may occur even in flat spacetime for the specific choice of the effective potential. The conditions for the avoidance of finite-time singularities are presented and discussed. The problem is reduced to the study of a scalar field evolving on an effective potential by using the conformal transformations. Some viable modified gravity models are analyzed in detail and the way to cure singularity is considered by introducing the higher-order curvature corrections. These results maybe relevant for the resolution of the conjectured problem in the relativistic star formation in such modified gravity where finite-time singularity is also manifested.
Oblique reflections of internal gravity wave beams
Karimi, Hussain H. (Hussain Habibullah)
2012-01-01T23:59:59.000Z
We study nonlinear effects in reflections of internal gravity wave beams in a continuously stratified liquid which are incident upon a uniform slope at an oblique angle. Wave motion in a stratified fluid medium is unique ...
Primordial Density Fluctuations in Phase Coupling Gravity
C. E. M. Batista; M. Schiffer
1996-01-10T23:59:59.000Z
In this paper we study the evolution of density perturbations in the framework of Phase Coupling Gravity theory at the very early universe. We show that these perturbation display an exponential-like behaviour.
Gravity waves from vortex dipoles and jets
Wang, Shuguang
2009-05-15T23:59:59.000Z
The dissertation first investigates gravity wave generation and propagation from jets within idealized vortex dipoles using a nonhydrostatic mesoscale model. Several initially balanced and localized jets induced by vortex dipoles are examined here...
A new vacuum for Loop Quantum Gravity
Bianca Dittrich; Marc Geiller
2015-05-05T23:59:59.000Z
We construct a new vacuum for loop quantum gravity, which is dual to the Ashtekar-Lewandowski vacuum. Because it is based on BF theory, this new vacuum is physical for $(2+1)$-dimensional gravity, and much closer to the spirit of spin foam quantization in general. To construct this new vacuum and the associated representation of quantum observables, we introduce a modified holonomy-flux algebra which is cylindrically consistent with respect to the notion of refinement by time evolution suggested in [1]. This supports the proposal for a construction of a physical vacuum made in [1,2], also for $(3+1)$-dimensional gravity. We expect that the vacuum introduced here will facilitate the extraction of large scale physics and cosmological predictions from loop quantum gravity.
State sum models for quantum gravity
John W. Barrett
2000-10-12T23:59:59.000Z
This paper reviews the construction of quantum field theory on a 4-dimensional spacetime by combinatorial methods, and discusses the recent developments in the direction of a combinatorial construction of quantum gravity.
Energy conditions in f(R) gravity
Santos, J. [Universidade Federal do Rio Grande do Norte, Departamento de Fisica C.P. 1641, 59072-970 Natal-Rio Grande do Norte (Brazil); Departamento de Astronomia, Observatorio Nacional, 20921-400 Rio de Janeiro-Rio de Janeiro (Brazil); Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro-Rio de Janeiro (Brazil); Alcaniz, J. S.; Carvalho, F. C. [Departamento de Astronomia, Observatorio Nacional, 20921-400 Rio de Janeiro-Rio de Janeiro (Brazil); Reboucas, M. J. [Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro-Rio de Janeiro (Brazil)
2007-10-15T23:59:59.000Z
In order to shed some light on the current discussion about f(R)-gravity theories we derive and discuss the bounds imposed by the energy conditions on a general f(R) functional form. The null and strong energy conditions in this framework are derived from Raychaudhuri's equation along with the requirement that gravity is attractive, whereas the weak and dominant energy conditions are stated from a comparison with the energy conditions that can be obtained in a direct approach via an effective energy-momentum tensor for f(R) gravity. As a concrete application of the energy conditions to locally homogeneous and isotropic f(R) cosmology, the recent estimated values of the deceleration and jerk parameters are used to examine the bounds from the weak energy condition on the parameters of two families of f(R)-gravity theories.
Cosmology of modified (but second order) gravity
Tomi S. Koivisto
2009-10-21T23:59:59.000Z
This is a brief review of modified gravity cosmologies. Generically extensions of gravity action involve higher derivative terms, which can result in ghosts and instabilities. There are three ways to circumvent this: Chern-Simons terms, first order variational principle and nonlocality. We consider recent cosmological applications of these three classes of modified gravity models, in particular to the dark energy problem. The viable parameter spaces can be very efficiently constrained by taking into account cosmological data from all epochs in addition to Solar system tests and stability considerations. We make some new remarks concerning so called algebraic scalar-tensor theories, biscalar reformulation of nonlocal actions involving the inverse d'Alembertian, and a possible covariant formulation holographic cosmology with nonperturbative gravity.
Energy conditions in f(R)-gravity
J. Santos; J. S. Alcaniz; M. J. Reboucas; F. C. Carvalho
2007-09-06T23:59:59.000Z
In order to shed some light on the current discussion about f(R)-gravity theories we derive and discuss the bounds imposed by the energy conditions on a general f(R) functional form. The null and strong energy conditions in this framework are derived from the Raychaudhuri's equation along with the requirement that gravity is attractive, whereas the weak and dominant energy conditions are stated from a comparison with the energy conditions that can be obtained in a direct approach via an effective energy-momentum tensor for f(R)-gravity. As a concrete application of the energy conditions to locally homogeneous and isotropic f(R)-cosmology, the recent estimated values of the deceleration and jerk parameters are used to examine the bounds from the weak energy condition on the parameters of two families of f(R)-gravity theories.
Test particle motion in modified gravity theories
Mahmood Roshan
2013-02-05T23:59:59.000Z
We derive the equations of motion of an electrically neutral test particle for modified gravity theories in which the covariant divergence of the ordinary matter energy-momentum tensor dose not vanish (i.e. $\
Anisotropic induced gravity and inflationary universe
W. F. Kao
2006-12-09T23:59:59.000Z
Existence and stability analysis of the Kantowski-Sachs type universe in a higher derivative induced gravity theory is studied in details. Existence of one stable mode and one unstable mode is shown to be in favor of the inflationary universe. As a result, the de Sitter background can be made to be stable against anisotropic perturbations with proper constraints imposed on the coupling constants of the induced gravity model.
Gravity waves from cosmic bubble collisions
Salem, Michael P.; Saraswat, Prashant; Shaghoulian, Edgar, E-mail: mpsalem@stanford.edu, E-mail: ps88@stanford.edu, E-mail: edgars@stanford.edu [Stanford Institute for Theoretical Physics and Department of Physics, Stanford University, Stanford, California 94305 (United States)
2013-02-01T23:59:59.000Z
Our local Hubble volume might be contained within a bubble that nucleated in a false vacuum with only two large spatial dimensions. We study bubble collisions in this scenario and find that they generate gravity waves, which are made possible in this context by the reduced symmetry of the global geometry. These gravity waves would produce B-mode polarization in the cosmic microwave background, which could in principle dominate over the inflationary background.
Gravity as Quantum Foam In-Flow
Reginald T Cahill
2003-07-01T23:59:59.000Z
The new information-theoretic Process Physics provides an explanation of space as a quantum foam system in which gravity is an inhomogeneous flow of the quantum foam into matter. The older Newtonian and General Relativity theories for gravity are analysed. It is shown that Newtonian gravity may be written in the form of an in-flow. General Relativity is also analysed as an in-flow, for those cases where it has been tested. An analysis of various experimental data demonstrates that absolute motion relative to space has been observed by Michelson and Morley, Miller, Illingworth, Jaseja et al, Torr and Kolen, and by DeWitte. The Dayton Miller and Roland DeWitte data also reveal the in-flow of space into matter which manifests as gravity. The experimental data suggests that the in-flow is turbulent, which amounts to the observation of a gravitational wave phenomena. A new in-flow theory of gravity is proposed which passes all the tests that General Relativity was claimed to have passed, but as well the new theory suggests that the so-called spiral galaxy rotation-velocity anomaly may be explained without the need of `dark matter'. Various other gravitational anomalies also appear to be explainable. Newtonian gravity appears to be strictly valid only outside of spherically symmetric matter systems.
Encoding field theories into gravities
Aoki, Sinya; Onogi, Tetsuya
2015-01-01T23:59:59.000Z
We propose a method, which encodes the information of a $d$ dimensional quantum field theory into a $d+1$ dimensional gravity in the $1/N$ expansion. We first construct a $d+1$ dimensional field theory from the $d$ dimensional one via the gradient flow equation, whose flow time $t$ represents the energy scale of the system such that $t\\rightarrow 0$ corresponds to the ultra-violet (UV) while $t\\rightarrow\\infty$ to the infra-red (IR). We then define the induced metric from $d+1$ dimensional field operators. We show that the metric defined in this way becomes classical in the large $N$ limit, in a sense that quantum fluctuations of the metric are suppressed as $1/N$ due to the large $N$ factorization property. As a concrete example, we apply our method to the O(N) non-linear $\\sigma$ model in two dimensions. We calculate the induced metric in three dimensions, which is shown to describe De Sitter (dS) or Anti De Sitter (AdS) space in the massless limit, where the mass is dynamically generated in the O(N) non-l...
Universality of Gravity from Entanglement
Brian Swingle; Mark Van Raamsdonk
2014-05-12T23:59:59.000Z
The entanglement "first law" in conformal field theories relates the entanglement entropy for a ball-shaped region to an integral over the same region involving the expectation value of the CFT stress-energy tensor, for infinitesimal perturbations to the CFT vacuum state. In recent work, this was exploited at leading order in $N$ in the context of large N holographic CFTs to show that any geometry dual to a perturbed CFT state must satisfy Einstein's equations linearized about pure AdS. In this note, we investigate the implications of the leading 1/N correction to the exact CFT result. We show that these corrections give rise to the source term for the gravitational equations: for semiclassical bulk states, the expectation value of the bulk stress-energy tensor appears as a source in the linearized equations. In particular, the CFT first law leads to Newton's Law of gravitation and the fact that all sources of stress-energy source the gravitational field. In our derivation, this universality of gravity comes directly from the universality of entanglement (the fact that all degrees of freedom in a subsystem contribute to entanglement entropy).
Bimetric gravity and dark matter
Laura Bernard; Luc Blanchet; Lavinia Heisenberg
2015-07-10T23:59:59.000Z
We review some recent proposals for relativistic models of dark matter in the context of bimetric gravity. The aim is to solve the problems of cold dark matter (CDM) at galactic scales, and to reproduce the phenomenology of the modified Newtonian dynamics (MOND), while still being in agreement with the standard cosmological model $\\Lambda$-CDM at large scales. In this context a promising alternative is dipolar dark matter (DDM) in which two different species of dark matter particles are separately coupled to the two metrics of bigravity and are linked together by an internal vector field. The phenomenology of MOND then results from a mechanism of gravitational polarization. Probably the best formulation of the model is within the framework of recently developed massive bigravity theories. Then the gravitational sector of the model is safe by construction, but a ghostly degree of freedom in the decoupling limit is still present in the dark matter sector. Future work should analyse the cosmological solutions of the model and check the post-Newtonian parameters in the solar system.
Quantum gravity and inventory accumulation
Scott Sheffield
2011-08-10T23:59:59.000Z
We begin by studying inventory accumulation at a LIFO (last-in-first-out) retailer with two products. In the simplest version, the following occur with equal probability at each time step: first product ordered, first product produced, second product ordered, second product produced. The inventory thus evolves as a simple random walk on Z^2. In more interesting versions, a p fraction of customers orders the "freshest available" product regardless of type. We show that the corresponding random walks scale to Brownian motions with diffusion matrices depending on p. We then turn our attention to the critical Fortuin-Kastelyn random planar map model, which gives, for each q>0, a probability measure on random (discretized) two-dimensional surfaces decorated by loops, related to the q-state Potts model. A longstanding open problem is to show that as the discretization gets finer, the surfaces converge in law to a limiting (loop-decorated) random surface. The limit is expected to be a Liouville quantum gravity surface decorated by a conformal loop ensemble, with parameters depending on q. Thanks to a bijection between decorated planar maps and inventory trajectories (closely related to bijections of Bernardi and Mullin), our results about the latter imply convergence of the former in a particular topology. A phase transition occurs at p = 1/2, q=4.
Measuring antimatter gravity with muonium
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Kaplan, Daniel M.; Kirch, Klaus; Mancini, Derrick; Phillips, James D.; Phillips, Thomas J.; Roberts, Thomas J.; Terry, Jeff; Bravina, L.; Foka, Y.; Kabana, S.
2015-05-29T23:59:59.000Z
The gravitational acceleration of antimatter, Żg, has never been directly measured and could bear importantly on our understanding of gravity, the possible existence of a fifth force, and the nature and early history of the universe. Only two avenues for such a measurement appear to be feasible: antihydrogen and muonium. The muonium measurement requires a novel, monoenergetic, low-velocity, horizontal muonium beam directed at an atom interferometer. The precision three-grating interferometer can be produced in silicon nitride or ultrananocrystalline diamond using state-of-the-art nanofabrication. The required precision alignment and calibration at the picometer level also appear to be feasible. With 100 nmmore ğgrating pitch, a 10% measurement of Żg can be made using some months of surface-muon beam time, and a 1% or better measurement with a correspondingly larger exposure. This could constitute the first gravitational measurement of leptonic matter, of 2nd-generation matter and, possibly, the first measurement of the gravitational acceleration of antimatter.Ğ less
Positive specific heat of the quantum corrected dilaton black hole
D. Grumiller; W. Kummer; D. V. Vassilevich
2003-06-20T23:59:59.000Z
Path integral quantization of dilaton gravity in two dimensions is applied to the CGHS model to the first nontrivial order in matter loops. Our approach is background independent as geometry is integrated out exactly. The result is an effective shift of the Killing norm: the apparent horizon becomes smaller. The Hawking temperature which is constant to leading order receives a quantum correction. As a consequence, the specific heat becomes positive and proportional to the square of the black hole mass.
A Kinetic Theory Approach to Quantum Gravity
B. L. Hu
2002-04-22T23:59:59.000Z
We describe a kinetic theory approach to quantum gravity -- by which we mean a theory of the microscopic structure of spacetime, not a theory obtained by quantizing general relativity. A figurative conception of this program is like building a ladder with two knotted poles: quantum matter field on the right and spacetime on the left. Each rung connecting the corresponding knots represent a distinct level of structure. The lowest rung is hydrodynamics and general relativity; the next rung is semiclassical gravity, with the expectation value of quantum fields acting as source in the semiclassical Einstein equation. We recall how ideas from the statistical mechanics of interacting quantum fields helped us identify the existence of noise in the matter field and its effect on metric fluctuations, leading to the establishment of the third rung: stochastic gravity, described by the Einstein-Langevin equation. Our pathway from stochastic to quantum gravity is via the correlation hierarchy of noise and induced metric fluctuations. Three essential tasks beckon: 1) Deduce the correlations of metric fluctuations from correlation noise in the matter field; 2) Reconstituting quantum coherence -- this is the reverse of decoherence -- from these correlation functions 3) Use the Boltzmann-Langevin equations to identify distinct collective variables depicting recognizable metastable structures in the kinetic and hydrodynamic regimes of quantum matter fields and how they demand of their corresponding spacetime counterparts. This will give us a hierarchy of generalized stochastic equations -- call them the Boltzmann-Einstein hierarchy of quantum gravity -- for each level of spacetime structure, from the macroscopic (general relativity) through the mesoscopic (stochastic gravity) to the microscopic (quantum gravity).
Testing Loop Quantum Gravity and Electromagnetic Dark Energy in Superconductors
Clovis Jacinto de Matos
2009-08-06T23:59:59.000Z
In 1989 Cabrera and Tate reported an anomalous excess of mass of the Cooper pairs in rotating thin Niobium rings. So far, this experimental result never received a proper theoretical explanation in the context of superconductor's physics. In the present work we argue that what Cabrera and Tate interpreted as an anomalous excess of mass can also be associated with a deviation from the classical gravitomagnetic Larmor theorem due to the presence of dark energy in the superconductor, as well as with the discrete structure of the area of the superconducting Niobium ring as predicted by Loop Quantum Gravity. From Cabrera and Tate measurements we deduce that the quantization of spacetime in superconducting circular rings occurs at the Planck-Einstein scale $l_{PE} = (\\hbar G/c^3 \\Lambda)^{1/4}\\sim 3.77\\times 10 ^{-5} m$, instead of the Planck scale $l_{P} =(\\hbar G / c^3)^{1/2}=1.61 \\times 10 ^{-35} m$, with an Immirzi parameter which depends on the specific critical temperature of the superconducting material and on the area of the ring. The stephan-Boltzmann law for quantized areas delimited by superconducting rings is predicted, and an experimental concept based on the electromagnetic black-body radiation emitted by this surfaces, is proposed to test loop quantum gravity and electromagnetic dark energy in superconductors.
Review on the quantization of gravity
Benjamin Schulz
2014-09-29T23:59:59.000Z
This is a review article on quantum gravity. In section 1, the Penrose singularity theorem is proven. In section 2, the covariant quantization approach of gravity is reviewed. In section 3, an article by Hawking is reviewed that shows the gravitational path integral at one loop level to be dominated by contributions from some kind of virtual gravitational instantons. In section 4, the canonical, non-perturbative quantization approach is reviewed. In section 5, arguments from Hawking are mentioned which show the gravitational path integral to be an approximate solution of the Wheeler deWitt equation. In section 6, the black hole entropy is derived in various ways. Section 6.1 uses the gravitational path integral for this calculation. Section 6.2 shows how the black hole entropy can be derived from canonical quantum gravity. In section 7.1, arguments from Dvali and Gomez who claim that gravity can be quantized in a way which would be in some sense self-complete are critically assessed. In section 7.2 a model from Dvali and Gomez for the description of quantum mechanical black holes is critically assessed and compared with the standard quantization methods of gravity.
Gravity as Quantum Foam In-Flow
Cahill, R T
2003-01-01T23:59:59.000Z
The new information-theoretic Process Physics provides an explanation of space as a quantum foam system in which gravity is an inhomogeneous flow of the quantum foam into matter. The older Newtonian and General Relativity theories for gravity are analysed. It is shown that Newtonian gravity may be written in the form of an in-flow. General Relativity is also analysed as an in-flow, for those cases where it has been tested. An analysis of various experimental data demonstrates that absolute motion relative to space has been observed by Michelson and Morley, Miller, Illingworth, Jaseja et al, Torr and Kolen, and by DeWitte. The Dayton Miller and Roland DeWitte data also reveal the in-flow of space into matter which manifests as gravity. The experimental data suggests that the in-flow is turbulent, which amounts to the observation of a gravitational wave phenomena. A new in-flow theory of gravity is proposed which passes all the tests that General Relativity was claimed to have passed, but as well the new theory...
Legacy Management Specific Training
Broader source: Energy.gov [DOE]
The following courses are specific to Legacy Management Employees, for more information about the courses below or to register for any of these courses please contact Chequita Johnson.
Energy-momentum distribution of a general plane symmetric spacetime in metric f(R) gravity
Morteza Yavari
2014-06-13T23:59:59.000Z
In this paper, the exact vacuum solution of a general plane symmetric spacetime is investigated in metric f(R) gravity with the assumption of constant Ricci scalar. For this solution, we have studied the generalized Landau-Lifshitz energy-momentum complex in this theory to determine the energy distribution expressions for some specific f(R) models. Also, we show that these models satisfy the constant curvature condition.
Gravity tests and the Pioneer anomaly
Marc-Thierry Jaekel; Serge Reynaud
2005-11-04T23:59:59.000Z
Experimental tests of gravity performed in the solar system show a good agreement with general relativity. The latter is however challenged by the Pioneer anomaly which might be pointing at some modification of gravity law at ranges of the order of the size of the solar system. We introduce a metric extension of general relativity which, while preserving the equivalence principle, modifies the coupling between curvature and stress tensors and, therefore, the metric solution in the solar system. The ``post-Einsteinian extension'' replaces Newton gravitation constant by two running coupling constants, which depend on the scale and differ in the sectors of traceless and traced tensors, so that the metric solution is characterized by two gravitation potentials. The extended theory has the capability to preserve compatibility with gravity tests while accounting for the Pioneer anomaly. It can also be tested by new experiments or, maybe, by having a new look at data of already performed experiments.
Solar System Constraints on Disformal Gravity Theories
Hiu Yan Ip; Jeremy Sakstein; Fabian Schmidt
2015-07-02T23:59:59.000Z
Disformal theories of gravity are scalar-tensor theories where the scalar couples derivatively to matter via the Jordan frame metric. These models have recently attracted interest in the cosmological context since they admit accelerating solutions. We derive the solution for a static isolated mass in generic disformal gravity theories and transform it into the parameterised post-Newtonian form. This allows us to investigate constraints placed on such theories by local tests of gravity. The tightest constraints come from preferred-frame effects due to the motion of the Solar System with respect to the evolving cosmological background field. The constraints we obtain improve upon the previous solar system constraints by two orders of magnitude, and constrain the scale of the disformal coupling for generic models to $\\mathcal{M} \\gtrsim 100$ eV. These constraints render all disformal effects irrelevant for cosmology.
Detailed balance in Horava-Lifshitz gravity
Gianluca Calcagni
2010-02-04T23:59:59.000Z
We study Horava-Lifshitz gravity in the presence of a scalar field. When the detailed balance condition is implemented, a new term in the gravitational sector is added in order to maintain ultraviolet stability. The four-dimensional theory is of a scalar-tensor type with a positive cosmological constant and gravity is nonminimally coupled with the scalar and its gradient terms. The scalar field has a double-well potential and, if required to play the role of the inflation, can produce a scale-invariant spectrum. The total action is rather complicated and there is no analog of the Einstein frame where Lorentz invariance is recovered in the infrared. For these reasons it may be necessary to abandon detailed balance. We comment on open problems and future directions in anisotropic critical models of gravity.
Solar System Constraints on Disformal Gravity Theories
Ip, Hiu Yan; Schmidt, Fabian
2015-01-01T23:59:59.000Z
Disformal theories of gravity are scalar-tensor theories where the scalar couples derivatively to matter via the Jordan frame metric. These models have recently attracted interest in the cosmological context since they admit accelerating solutions. We derive the solution for a static isolated mass in generic disformal gravity theories and transform it into the parameterised post-Newtonian form. This allows us to investigate constraints placed on such theories by local tests of gravity. The tightest constraints come from preferred-frame effects due to the motion of the Solar System with respect to the evolving cosmological background field. The constraints we obtain improve upon the previous solar system constraints by two orders of magnitude, and constrain the scale of the disformal coupling for generic models to $\\mathcal{M} \\gtrsim 100$ eV. These constraints render all disformal effects irrelevant for cosmology.
Emergence in Holographic Scenarios for Gravity
Dieks, Dennis; de Haro, Sebastian
2015-01-01T23:59:59.000Z
'Holographic' relations between theories have become an important theme in quantum gravity research. These relations entail that a theory without gravity is equivalent to a gravitational theory with an extra spatial dimension. The idea of holography was first proposed in 1993 by Gerard 't Hooft on the basis of his studies of evaporating black holes. Soon afterwards the holographic 'AdS/CFT' duality was introduced, which since has been intensively studied in the string theory community and beyond. Recently, Erik Verlinde has proposed that even Newton's law of gravitation can be related holographically to the 'thermodynamics of information' on screens. We discuss these scenarios, with special attention to the status of the holographic relation in them and to the question of whether they make gravity and spacetime emergent. We conclude that only Verlinde's scheme straightfowardly instantiates emergence. However, assuming a non-standard interpretation of AdS/CFT may create room for the emergence of spacetime and ...
Quantum gravity effects in the Kerr spacetime
Reuter, M. [Institute of Physics, University of Mainz, Staudingerweg 7, D-55099 Mainz (Germany); Tuiran, E. [Departamento de Fisica, Universidad del Norte, Km 5 via a Puerto Colombia, AA-1569 Barranquilla (Colombia)
2011-02-15T23:59:59.000Z
We analyze the impact of the leading quantum gravity effects on the properties of black holes with nonzero angular momentum by performing a suitable renormalization group improvement of the classical Kerr metric within quantum Einstein gravity. In particular, we explore the structure of the horizons, the ergosphere, and the static limit surfaces as well as the phase space available for the Penrose process. The positivity properties of the effective vacuum energy-momentum tensor are also discussed and the 'dressing' of the black hole's mass and angular momentum are investigated by computing the corresponding Komar integrals. The pertinent Smarr formula turns out to retain its classical form. As for their thermodynamical properties, a modified first law of black-hole thermodynamics is found to be satisfied by the improved black holes (to second order in the angular momentum); the corresponding Bekenstein-Hawking temperature is not proportional to the surface gravity.
Planck 2015 results. XIV. Dark energy and modified gravity
Ade, P A R; Arnaud, M; Ashdown, M; Aumont, J; Baccigalupi, C; Banday, A J; Barreiro, R B; Bartolo, N; Battaner, E; Battye, R; Benabed, K; Benoît, A; Benoit-Lévy, A; Bernard, J -P; Bersanelli, M; Bielewicz, P; Bonaldi, A; Bonavera, L; Bond, J R; Borrill, J; Bouchet, F R; Bucher, M; Burigana, C; Butler, R C; Calabrese, E; Cardoso, J -F; Catalano, A; Challinor, A; Chamballu, A; Chiang, H C; Christensen, P R; Church, S; Clements, D L; Colombi, S; Colombo, L P L; Combet, C; Couchot, F; Coulais, A; Crill, B P; Curto, A; Cuttaia, F; Danese, L; Davies, R D; Davis, R J; de Bernardis, P; de Rosa, A; de Zotti, G; Delabrouille, J; Désert, F -X; Diego, J M; Dole, H; Donzelli, S; Doré, O; Douspis, M; Ducout, A; Dupac, X; Efstathiou, G; Elsner, F; Enßlin, T A; Eriksen, H K; Fergusson, J; Finelli, F; Forni, O; Frailis, M; Fraisse, A A; Franceschi, E; Frejsel, A; Galeotta, S; Galli, S; Ganga, K; Giard, M; Giraud-Héraud, Y; Gjerlĝw, E; González-Nuevo, J; Górski, K M; Gratton, S; Gregorio, A; Gruppuso, A; Gudmundsson, J E; Hansen, F K; Hanson, D; Harrison, D L; Heavens, A; Helou, G; Henrot-Versillé, S; Hernández-Monteagudo, C; Herranz, D; Hildebrandt, S R; Hivon, E; Hobson, M; Holmes, W A; Hornstrup, A; Hovest, W; Huang, Z; Huffenberger, K M; Hurier, G; Jaffe, A H; Jaffe, T R; Jones, W C; Juvela, M; Keihänen, E; Keskitalo, R; Kisner, T S; Knoche, J; Kunz, M; Kurki-Suonio, H; Lagache, G; Lähteenmäki, A; Lamarre, J -M; Lasenby, A; Lattanzi, M; Lawrence, C R; Leonardi, R; Lesgourgues, J; Levrier, F; Lewis, A; Liguori, M; Lilje, P B; Linden-Vĝrnle, M; López-Caniego, M; Lubin, P M; Ma, Y -Z; Macías-Pérez, J F; Maggio, G; Mandolesi, N; Mangilli, A; Marchini, A; Martin, P G; Martinelli, M; Martínez-González, E; Masi, S; Matarrese, S; Mazzotta, P; McGehee, P; Meinhold, P R; Melchiorri, A; Mendes, L; Mennella, A; Migliaccio, M; Mitra, S; Miville-Deschênes, M -A; Moneti, A; Montier, L; Morgante, G; Mortlock, D; Moss, A; Munshi, D; Murphy, J A; Narimani, A; Naselsky, P; Nati, F; Natoli, P; Netterfield, C B; Nĝrgaard-Nielsen, H U; Noviello, F; Novikov, D; Novikov, I; Oxborrow, C A; Paci, F; Pagano, L; Pajot, F; Paoletti, D; Pasian, F; Patanchon, G; Pearson, T J; Perdereau, O; Perotto, L; Perrotta, F; Pettorino, V; Piacentini, F; Piat, M; Pierpaoli, E; Pietrobon, D; Plaszczynski, S; Pointecouteau, E; Polenta, G; Popa, L; Pratt, G W; Prézeau, G; Prunet, S; Puget, J -L; Rachen, J P; Reach, W T; Rebolo, R; Reinecke, M; Remazeilles, M; Renault, C; Renzi, A; Ristorcelli, I; Rocha, G; Rosset, C; Rossetti, M; Roudier, G; Rowan-Robinson, M; Rubiño-Martín, J A; Rusholme, B; Salvatelli, V; Sandri, M; Santos, D; Savelainen, M; Savini, G; Schaefer, B M; Scott, D; Seiffert, M D; Shellard, E P S; Spencer, L D; Stolyarov, V; Stompor, R; Sudiwala, R; Sunyaev, R; Sutton, D; Suur-Uski, A -S; Sygnet, J -F; Tauber, J A; Terenzi, L; Toffolatti, L; Tomasi, M; Tristram, M; Tucci, M; Tuovinen, J; Valenziano, L; Valiviita, J; Van Tent, B; Viel, M; Vielva, P; Villa, F; Wade, L A; Wandelt, B D; Wehus, I K; White, M; Yvon, D; Zacchei, A; Zonca, A
2015-01-01T23:59:59.000Z
We study the implications of Planck data for models of dark energy (DE) and modified gravity (MG), beyond the cosmological constant scenario. We start with cases where the DE only directly affects the background evolution, considering Taylor expansions of the equation of state, principal component analysis and parameterizations related to the potential of a minimally coupled DE scalar field. When estimating the density of DE at early times, we significantly improve present constraints. We then move to general parameterizations of the DE or MG perturbations that encompass both effective field theories and the phenomenology of gravitational potentials in MG models. Lastly, we test a range of specific models, such as k-essence, f(R) theories and coupled DE. In addition to the latest Planck data, for our main analyses we use baryonic acoustic oscillations, type-Ia supernovae and local measurements of the Hubble constant. We further show the impact of measurements of the cosmological perturbations, such as redshif...
Stratospheric gravity wave simulation over Greenland during 24 January 2005
Limpasuvan, Varavut
gravity waves because of imbalance of the jet stream. Where the horizontal jet is rapidly changing speed anticyclonic jet stream over the North Atlantic. Likewise, inertia gravity waves can result from synoptic
Ground Gravity Survey At Baltazor Hot Springs Area (Isherwood...
gravity low within the valley area that presumably is related to low-density Cenozoic sediments. The steep gravity gradient along the east side of the valley suggests a...
Theoretical and experimental study of nonlinear internal gravity wave beams
Tabaei Befrouei, Ali, 1974-
2005-01-01T23:59:59.000Z
Continuously stratified fluids, like the atmosphere and the oceans, support internal gravity waves due to the effect of buoyancy. This type of wave motion is anisotropic since gravity provides a preferred direction. As a ...
Gravity modeling of Cenozoic extensional basins, offshore Vietnam
Mauri, Steven Joseph
1993-01-01T23:59:59.000Z
Integrating Bouguer gravity and satellite-derived free-air gravity data with published geological and geophysical data allows modeling crustal structure and estimating crustal extension for the hydrocarbon bearing Mekong ...
The inverse-square law and quantum gravity
Nieto, M.M.; Goldman, T.; Hughes, R.J.
1988-01-01T23:59:59.000Z
This paper briefly discusses a modification to central potential of gravity when antimatter is involved and the possible existence of quantum gravity and a fifth force of nature. 1 ref. (LSP)
Prima Facie Questions in Quantum Gravity
C. J. Isham
1993-10-22T23:59:59.000Z
The long history of the study of quantum gravity has thrown up a complex web of ideas and approaches. The aim of this article is to unravel this web a little by analysing some of the {\\em prima facie\\/} questions that can be asked of almost any approach to quantum gravity and whose answers assist in classifying the different schemes. Particular emphasis is placed on (i) the role of background conceptual and technical structure; (ii) the role of spacetime diffeomorphisms; and (iii) the problem of time.
Linear Stability Analysis of Dynamical Quadratic Gravity
Dimitry Ayzenberg; Kent Yagi; Nicolas Yunes
2014-03-18T23:59:59.000Z
We perform a linear stability analysis of dynamical, quadratic gravity in the high-frequency, geometric optics approximation. This analysis is based on a study of gravitational and scalar modes propagating on spherically-symmetric and axially-symmetric, vacuum solutions of the theory. We find dispersion relations that do no lead to exponential growth of the propagating modes, suggesting the theory is linearly stable on these backgrounds. The modes are found to propagate at subluminal and superluminal speeds, depending on the propagating modes' direction relative to the background geometry, just as in dynamical Chern-Simons gravity.
Nonlocal Gravity in the Solar System
Chicone, C
2015-01-01T23:59:59.000Z
The implications of the recent classical nonlocal generalization of Einstein's theory of gravitation for gravitational physics in the Solar System are investigated. In this theory, the nonlocal character of gravity simulates dark matter. Nonlocal gravity in the Newtonian regime involves a reciprocal kernel with three spatial parameters, of which two have already been determined from the rotation curves of spiral galaxies and the internal dynamics of clusters of galaxies. However, the short-range parameter a_0 remains to be determined. In this connection, the nonlocal contribution to the perihelion precession of a planetary orbit is estimated and a preliminary lower limit on a_0 is determined.
Holographic superconductors from the massive gravity
Hua Bi Zeng; Jian-Pin Wu
2014-09-24T23:59:59.000Z
A holographic superconductor is constructed in the background of a massive gravity theory. In the normal state without condensation, the conductivity exhibits a Drude peak that approaches a delta function in the massless gravity limit as studied by David Vegh. In the superconducting state, besides the infinite DC conductivity, the AC conductivity has Drude behavior at low frequency followed by a power law-fall. These results are in agreement with that found earlier by Horowitz and Santos, who studied a holographic superconductor with an implicit periodic potential beyond the probe limit. The results also agree with measurements on some cuprates.
Weak Gravity Conjecture for Noncommutative Field Theory
Qing-Guo Huang; Jian-Huang She
2006-11-20T23:59:59.000Z
We investigate the weak gravity bounds on the U(1) gauge theory and scalar field theories in various dimensional noncommutative space. Many results are obtained, such as the upper bound on the noncommutative scale $g_{YM}M_p$ for four dimensional noncommutative U(1) gauge theory. We also discuss the weak gravity bounds on their commutative counterparts. For example, our result on 4 dimensional noncommutative U(1) gauge theory reduces in certain limit to its commutative counterpart suggested by Arkani-Hamed et.al at least at tree-level.
Energy Distribution in f(R) Gravity
M. Sharif; M. Farasat Shamir
2009-12-18T23:59:59.000Z
The well-known energy problem is discussed in f(R) theory of gravity. We use the generalized Landau-Lifshitz energy-momentum complex in the framework of metric f(R) gravity to evaluate the energy density of plane symmetric solutions for some general f(R) models. In particular, this quantity is found for some popular choices of f(R) models. The constant scalar curvature condition and the stability condition for these models are also discussed. Further, we investigate the energy distribution of cosmic string spacetime.
Violation of Energy Bounds in Designer Gravity
Thomas Hertog
2006-07-31T23:59:59.000Z
We continue our study of the stability of designer gravity theories, where one considers anti-de Sitter gravity coupled to certain tachyonic scalars with boundary conditions defined by a smooth function W. It has recently been argued there is a lower bound on the conserved energy in terms of the global minimum of W, if the scalar potential arises from a superpotential P and the scalar reaches an extremum of P at infinity. We show, however, there are superpotentials for which these bounds do not hold.
Multidimensional Gravity on the Principal Bundles
V. D. Dzhunushaliev
1997-11-10T23:59:59.000Z
The multidimensional gravity on the total space of principal bundle is considered. In this theory the gauge fields arise as nondiagonal components of multidimensional metric. The spherically symmetric and cosmology solutions for gravity on SU(2) principal bundle are obtained. The static spherically symmetric solution is wormhole-like solution located between two null surfaces, in contrast to 4D Einstein-Yang-Mills theory where corresponding solution (black hole) located outside of event horizon. Cosmology solution (at least locally) has the bouncing off effect for spatial dimensions. In spirit of Einstein these solutions are vacuum solutions without matter.
Hogg, Charlie A. R.; Dalziel, Stuart B.; Huppert, Herbert E.; Imberger, Jörg
2015-01-01T23:59:59.000Z
by noise in the conductivity measurements which was minimised by the median 10 Gravity currents filling basins: influence of Reynolds number on entrainment Source x z Outflow ? D zf A = D/(sin ? cos ?) FIG. 6: Schematic of the basin. The gravity current... in these experiments, the horizontal length at the top of the basin is A = D/(sin ? cos ?) . The virtual origin is the origin for a source of buoyancy alone that would give rise to the volume and buoyancy flux that occurs at the physical origin. 12 Gravity currents...
Nordstrom's scalar theory of gravity and the equivalence principle
Nathalie Deruelle
2011-04-24T23:59:59.000Z
Nordstrom's theory of gravity, which describes gravity by a scalar field in flat spacetime, is observationally ruled out. It is however the only theory of gravity with General Relativity to obey the strong equivalence principle. I show in this paper that this remarkable property is true beyond post-newtonian level and can be related to the existence of a 'Nordstrom-Katz' superpotential.
Gravity Wave Lensing Ryan Elandt, Mostafa Shakeri & Reza Alam
Alam, Mohammad-Reza
Gravity Wave Lensing Ryan Elandt, Mostafa Shakeri & Reza Alam Department of Mechanical Engineering waves caused by small seabed features (the so called Bragg resonance) can be utilized to create equivalent of lenses and curved mirrors for surface gravity waves. Such gravity wave lenses, which are merely
Generalized $f(R,?,X)$ gravity and the late-time cosmic acceleration
Sebastian Bahamonde Beltran; Christian G. Boehmer; Francisco S. N. Lobo; Diego Saez-Gomez
2015-06-25T23:59:59.000Z
High-precision observational data have confirmed with startling evidence that the Universe is currently undergoing a phase of accelerated expansion. This phase, one of the most important and challenging current problems in cosmology, represents a new imbalance in the governing gravitational equations. Historically, physics has addressed such imbalances by either identifying sources that were previously unaccounted for, or by altering the gravitational theory. Several candidates, responsible for this expansion, have been proposed in the literature, in particular, dark energy models and modified gravity models, amongst others. Outstanding questions are related to the nature of this so-called "dark energy" that is driving this acceleration, and whether it is due to the vacuum energy or a dynamical field. On the other hand, the late-time cosmic acceleration may be due to modifications of General Relativity. In this work we explore a generalised modified gravity theory, namely $f(R,\\phi,X)$ gravity, where $R$ is the Ricci scalar, $\\phi$ is a scalar field, and $X$ is a kinetic term. This theory contains a wide range of dark energy and modified gravity models. We considered specific models and applications to the late-time cosmic acceleration.
Post-Minkowskian Limit and Gravitational Waves solutions of Fourth Order Gravity: a complete study
A. Stabile; S. Capozziello
2015-04-26T23:59:59.000Z
The post-Minkowskian limit and gravitational wave solutions for general fourth-order gravity theories are discussed. Specifically, we consider a Lagrangian with a generic function of curvature invariants $f(R, R_{\\alpha\\beta}R^{\\alpha\\beta}, R_{\\alpha\\beta\\gamma\\delta}R^{\\alpha\\beta\\gamma\\delta})$. It is well known that when dealing with General Relativity such an approach provides massless spin-two waves as propagating degree of freedom of the gravitational field while this theory implies other additional propagating modes in the gravity spectra. We show that, in general, fourth order gravity, besides the standard massless graviton is characterized by two further massive modes with a finite-distance interaction. We find out the most general gravitational wave solutions in terms of Green functions in vacuum and in presence of matter sources. If an electromagnetic source is chosen, only the modes induced by $R_{\\alpha\\beta}R^{\\alpha\\beta}$ are present, otherwise, for any $f(R)$ gravity model, we have the complete analogy with tensor modes of General Relativity. Polarizations and helicity states are classified in the hypothesis of plane wave.
The Mars Gravity Biosatellite as an innovative partial gravity research platform
Fulford-Jones, Thaddeus R. F
2008-01-01T23:59:59.000Z
The Mars Gravity Biosatellite is an unprecedented independent spaceflight platform for gravitational biology research. With a projected first launch after 2010, the low Earth orbit satellite will support a cohort of fifteen ...
Webb, Spahr C.
, Petrologic and Seismic Expedition (GLIMPSE) study area from seismic refraction data R. Chadwick Holmes,1, Intraplate Melting, Petrologic and Seismic Expedition (GLIMPSE) experiment investigated the velocity in the Gravity Lineations, Intraplate Melting, Petrologic and Seismic Expedition (GLIMPSE) study area from
Topological Black Holes in Quantum Gravity
J. Kowalski-Glikman; D. Nowak-Szczepaniak
2000-07-31T23:59:59.000Z
We derive the black hole solutions with horizons of non-trivial topology and investigate their properties in the framework of an approach to quantum gravity being an extension of Bohm's formulation of quantum mechanics. The solutions we found tend asymptotically (for large $r$) to topological black holes. We also analyze the thermodynamics of these space-times.
Energy definition for quadratic curvature gravities
Ahmet Baykal
2012-12-03T23:59:59.000Z
A conserved current for generic quadratic curvature gravitational models is defined, and it is shown that, at the linearized level, it corresponds to the Deser-Tekin charges. An explicit expression for the charge for new massive gravity in three dimensions is given. Some implications of the linearized equations are discussed.
Running Coupling Constants in 2D Gravity
Christof Schmidhuber
1993-08-26T23:59:59.000Z
The renormalization group flow in two--dimensional field theories that are coupled to gravity is discussed at the example of the sine-Gordon model. In order to derive the phase diagram in agreement with the matrix model results, it is necessary to generalize the theory of David, Distler and Kawai.
Second order noncommutative corrections to gravity
Calmet, Xavier [Universite Libre de Bruxelles, Service de Physique Theorique, CP225 Boulevard du Triomphe (Campus plaine), B-1050 Brussels (Belgium); Kobakhidze, Archil [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599 (United States)
2006-08-15T23:59:59.000Z
In this work, we calculate the leading order corrections to general relativity formulated on a canonical noncommutative spacetime. These corrections appear in the second order of the expansion in theta. First order corrections can only appear in the gravity-matter interactions. Some implications are briefly discussed.
The diffeomorphism algebra approach to quantum gravity
T. A. Larsson
1999-09-13T23:59:59.000Z
The representation theory of non-centrally extended Lie algebras of Noether symmetries, including spacetime diffeomorphisms and reparametrizations of the observer's trajectory, has recently been developped. It naturally solves some long-standing problems in quantum gravity, e.g. the role of diffeomorphisms and the causal structure, but some new questions also arise.
p-wave superconductors in dilaton gravity
ZhongYing Fan
2013-10-08T23:59:59.000Z
In this paper, we study peculiar properties of p-wave superconductors in dilaton gravity. The scale invariance of the bulk geometry is effectively broken due to the existence of dilaton. By coupling the dilaton to the non-Abelian gauge field, i.e., $-\\frac14 e^{-\\beta \\Phi} F^a_{\\mu\
Topology in 4D simplicial quantum gravity
S. Bilke; Z. Burda; B. Petersson
1996-11-22T23:59:59.000Z
We simulate 4d simplicial gravity for three topologis S4, S3xS1, (S1)^4 and show that the free energy for these three fixed topology ensembles is the same in the thermodynamic limit. We show, that the next-to-leading order corrections, at least away from the critical point, can be described by kinematic sources.
Redesigning specificity in miniproteins
Taylor, Christina Marie
2006-01-01T23:59:59.000Z
This work focuses on designing specific miniprotein interactions using computational models and then testing these designs with experiments. Miniproteins are small, autonomously-folding proteins that are excellent for ...
Measuring the Earth's gravity field with cold atom interferometers
Carraz, Olivier; Massotti, Luca; Haagmans, Roger; Silvestrin, Pierluigi
2015-01-01T23:59:59.000Z
The scope of the paper is to propose different concepts for future space gravity missions using Cold Atom Interferometers (CAI) for measuring the diagonal elements of the gravity gradient tensor, the spacecraft angular velocity and the spacecraft acceleration. The aim is to achieve better performance than previous space gravity missions due to a very low white noise spectral behaviour of the CAI instrument and a very high common mode rejection, with the ultimate goals of determining the fine structures of the gravity field with higher accuracy than GOCE and detecting time-variable signals in the gravity field.
An improved method for the determination of the wellstream gas specific gravity for retrograde gases
Gold, David Keith
1988-01-01T23:59:59.000Z
VALENT (VEQn 8 fiSTS F t g . 5-VEll Model 2 Correlation Nomograph for a Two- stage Separat&on System. 20 ANALYSIS OF THE CORRELATIONS A variety of statistical analyses was performed on the AGP and VEQ correlations and the subsequent calculation... Combinations . . 1Z 3 Coefficients of Determination (R-squared) for the Models 21 4 Analysis of AGP Correlations for a Three-stage Separation System . . . . . . . . . . . . . . . . . . . . . . . . . 35 5 Analysis of vEO correlations for a Three...
New correlations for dew-point, specific gravity and producing yield for gas condensates
Ovalle Cortissoz, Adriana Patricia
2002-01-01T23:59:59.000Z
at reservoir temperature using readily available field data. There have been several attempts to correlate dew point pressures to original reservoir gas composition. The results have been reasonably accurate, but there was no evidence in the literature that a...
Relationship between specific gravity and quality attributes of "Tifblue" rabbiteye blueberries
Scheuerman, Mark Ronald
1987-01-01T23:59:59.000Z
. 186 60 Slc 60. 26~ 70. 794 75. 12e 2. 63s 2. 62s 2. 66~ 2 716 2. 90c 2. 91c 5. 50s 5. 14h 3. 59~ 3. 48~ 1. 884 1. 57e 33. 29s 34. 546 21. 78o 23. 434 10. 49~ 9. 51r 83. 47a 85. 126 83. 57~ 85. 17b 82. 06~ 83. 43a Harvests... 9 30b 41. 14 e 46, 18b 58. 29c 2. 64e b 5. 5pe 2. 62e 5 14b 2. 65e b 3. 80? 9 13b, c 6p 38c, d 2 74? 3. 88? 10. 20d 61. 89d 2. 69 3. 66 10. 45d s. soc 10. 40d 12 07e 12. 20e 12. 10 e 12. 17e 12. 93r 12. 23e 13. 73v 13. 20r 61. 48d 2...
Rotating black holes in a draining bathtub: superradiant scattering of gravity waves
Mauricio Richartz; Angus Prain; Stefano Liberati; Silke Weinfurtner
2015-06-05T23:59:59.000Z
In a draining rotating fluid flow background, surface perturbations behave as a scalar field on a rotating effective black hole spacetime. We propose a new model for the background flow which takes into account the varying depth of the water. Numerical integration of the associated Klein-Gordon equation using accessible experimental parameters shows that gravity waves in an appropriate frequency range are amplified through the mechanism of superradiance. Our numerical results suggest that the observation of this phenomenon in a common fluid mechanical system is within experimental reach. Unlike the case of wave scattering around Kerr black holes, which depends only on one dimensionless background parameter (the ratio $a/M$ between the specific angular momentum and the mass of the black hole), our system depends on two dimensionless background parameters, namely the normalized angular velocity and surface gravity at the effective black hole horizon.
Deep-water gravity waves: nonlinear theory of wave groups
Mindlin, I M
2014-01-01T23:59:59.000Z
Nonlinear initial-boundary value problem on deep-water gravity waves of finite amplitude is solved approximately (up to small terms of higher order) assuming that the waves are generated by an initial disturbance to the water and the horizontal dimensions of the initially disturbed body of the water are much larger than the magnitude of the free surface displacement. A numerable set of specific free surface waves is obtained in closed form and it is shown that free surface waves produced by an arbitrary initial disturbance to the water is a combination (not superposition: the waves are nonlinear) of the specific waves. A set of dispersive wave packets is found with one-to-one correspondence between the packets and positive integers, say, packet numbers, such that any initial free surface displacement gradually disintegrates into a number (limited or unlimited, depending on initial conditions) of the wave packets. The greater the packet number, the shorter the wavelength of the packet's carrier wave component,...
Conceptual Aspects of Gauge/Gravity Duality
de Haro, Sebastian; Butterfield, Jeremy
2015-01-01T23:59:59.000Z
We give an introductory review of gauge/gravity duality, and associated ideas of holography, emphasising the conceptual aspects. The opening Sections gather the ingredients, viz. anti-de Sitter spacetime, conformal field theory and string theory, that we need for presenting, in Section 5, the central and original example: Maldacena's AdS/CFT correspondence. Sections 6 and 7 develop the ideas of this example, also in applications to condensed matter systems, QCD, and hydrodynamics. Sections 8 and 9 discuss the possible extensions of holographic ideas to de Sitter spacetime and to black holes. Section 10 discusses the bearing of gauge/gravity duality on two philosophical topics: the equivalence of physical theories, and the idea that spacetime, or some features of it, are emergent.
Hydrogen atom in Palatini theories of gravity
Gonzalo J. Olmo
2008-06-03T23:59:59.000Z
We study the effects that the gravitational interaction of $f(R)$ theories of gravity in Palatini formalism has on the stationary states of the Hydrogen atom. We show that the role of gravity in this system is very important for lagrangians $f(R)$ with terms that grow at low curvatures, which have been proposed to explain the accelerated expansion rate of the universe. We find that new gravitationally induced terms in the atomic Hamiltonian generate a strong backreaction that is incompatible with the very existence of bound states. In fact, in the 1/R model, Hydrogen disintegrates in less than two hours. The universe that we observe is, therefore, incompatible with that kind of gravitational interaction. Lagrangians with high curvature corrections do not lead to such instabilities.
Quantum Gravity models - brief conceptual summary
Jerzy Lukierski
2014-11-27T23:59:59.000Z
After short historical overview we describe the difficulties with application of standard QFT methods in quantum gravity (QG). The incompatibility of QG with the use of classical continuous space-time required conceptually new approach. We present briefly three proposals: loop quantum gravity (LQG), the field-theoretic framework on noncommutative space-time and QG models formulated on discretized (triangularized) space-time. We evaluate these models as realizing expected important properties of QG: background independence, consistent quantum diffeomorphisms, noncommutative or discrete structure of space-time at very short distances, finite/renormalizable QG corrections. We only briefly outline an important issue of embedding QG into larger geometric and dynamical frameworks (e.g. supergravity, (super)strings, p-branes, M-theory), with the aim to achieve full unification of all fundamental interactions.
Chaotic inflation in higher derivative gravity theories
Myrzakul, Shynaray; Sebastiani, Lorenzo
2015-01-01T23:59:59.000Z
In this paper, we investigate chaotic inflation from scalar field subjected to potential in the framework of $f(R^2, P, Q)$-gravity, where we add a correction to Einstein's gravity based on a function of the square of the Ricci scalar $R^2$, the contraction of the Ricci tensor $P$, and the contraction of the Riemann tensor $Q$. The Gauss-Bonnet case is also discussed. We give the general formalism of inflation, deriving the slow-roll parameters, the $e$-folds number, and the spectral indexes. Several explicit examples are furnished, namely we will consider the cases of massive scalar field and scalar field with quartic potential and some power-law function of the curvature invariants under investigation in the gravitational action of the theory. Viable inflation according with observations is analyzed.
Infrared modification of gravity from conformal symmetry
Gegenberg, Jack; Seahra, Sanjeev S
2015-01-01T23:59:59.000Z
We reconsider a gauge theory of gravity in which the gauge group is the conformal group SO(4,2) and the action is of the Yang-Mills form, quadratic in the curvature. The resulting gravitational theory exhibits local conformal symmetry and reduces to Weyl-squared gravity under certain conditions. When the theory is linearized about flat spacetime, we find that matter which couples to the generators of special conformal transformations reproduces Newton's inverse square law. Conversely, matter which couples to generators of translations induces a constant and possibly repulsive force far from the source, which may be relevant for explaining the late time acceleration of the universe. The coupling constant of theory is dimensionless, which means that it is potentially renormalizable.
IDC System Specification Document.
Clifford, David J.
2014-12-01T23:59:59.000Z
This document contains the system specifications derived to satisfy the system requirements found in the IDC System Requirements Document for the IDC Reengineering Phase 2 project. Revisions Version Date Author/Team Revision Description Authorized by V1.0 12/2014 IDC Reengineering Project Team Initial delivery M. Harris
Charged Cylindrical Black Holes in Conformal Gravity
Jackson Levi Said; Joseph Sultana; Kristian Zarb Adami
2013-01-04T23:59:59.000Z
Considering cylindrical topology we present the static solution for a charged black hole in conformal gravity. We show that unlike the general relativistic case there are two different solutions, both including a factor that when set to zero recovers the familiar static charged black string solution in Einstein's theory. This factor gives rise to a linear term in the potential that also features in the neutral case and may have significant ramifications for particle trajectories.
Exact Gravity Dual of a Gapless Superconductor
George Koutsoumbas; Eleftherios Papantonopoulos; George Siopsis
2009-06-17T23:59:59.000Z
A model of an exact gravity dual of a gapless superconductor is presented in which the condensate is provided by a charged scalar field coupled to a bulk black hole of hyperbolic horizon in asymptotically AdS spacetime. Below a critical temperature, the black hole acquires its hair through a phase transition while an electromagnetic perturbation of the background Maxwell field determines the conductivity of the boundary theory.
Holographic Superconductivity with Gauss-Bonnet gravity
Ruth Gregory
2010-12-07T23:59:59.000Z
I review recent work on holographic superconductivity with Einstein-Gauss-Bonnet gravity, and show how the critical temperature of the superconductor depends on both gravitational backreaction and the Gauss-Bonnet parameter, using both analytic and numerical arguments. I also review computations of the conductivity, finding the energy gap, and demonstrating that there is no universal gap ratio, $\\omega_g/T_c$, for these superconductors.
Holographic Superconductors in Horava-Lifshitz Gravity
Kai Lin; Elcio Abdalla; Anzhong Wang
2014-06-18T23:59:59.000Z
We consider holographic superconductors related to the Schwarzschild black hole in the low energy limit of Ho\\v{r}ava-Lifshitz spacetime. The non-relativistic electromagnetic and scalar fields are introduced to construct a holographic superconductor model in Ho\\v{r}ava-Lifshitz gravity and the results show that the $\\alpha_2$ term plays an important role, modifying the conductivity curve line by means of an attenuation the conductivity.
Gravity controlled anti-reverse rotation device
Dickinson, Robert J. (Shaler Township, Allegheny County, PA); Wetherill, Todd M. (Lower Burrell, PA)
1983-01-01T23:59:59.000Z
A gravity assisted anti-reverse rotation device for preventing reverse rotation of pumps and the like. A horizontally mounted pawl is disposed to mesh with a fixed ratchet preventing reverse rotation when the pawl is advanced into intercourse with the ratchet by a vertically mounted lever having a lumped mass. Gravitation action on the lumped mass urges the pawl into mesh with the ratchet, while centrifugal force on the lumped mass during forward, allowed rotation retracts the pawl away from the ratchet.
QPOs: Einstein's gravity non-linear resonances
Paola Rebusco; Marek A. Abramowicz
2006-01-30T23:59:59.000Z
There is strong evidence that the observed kHz Quasi Periodic Oscillations (QPOs) in the X-ray flux of neutron star and black hole sources in LMXRBs are linked to Einstein's General Relativity. Abramowicz&Klu\\'zniak (2001) suggested a non-linear resonance model to explain the QPOs origin: here we summarize their idea and the development of a mathematical toy-model which begins to throw light on the nature of Einstein's gravity non-linear oscillations.
Gravity and Yang-Mills amplitude relations
Bjerrum-Bohr, N. E. J.; Damgaard, Poul H.; Soendergaard, Thomas [Niels Bohr International Academy and Discovery Center, Niels Bohr Institute, Blegdamsvej 17, DK-2100, Copenhagen O (Denmark); FengBo [Center of Mathematical Science, Zhejiang University, Hangzhou (China)
2010-11-15T23:59:59.000Z
Using only general features of the S matrix and quantum field theory, we prove by induction the Kawai-Lewellen-Tye relations that link products of gauge theory amplitudes to gravity amplitudes at tree level. As a bonus of our analysis, we provide a novel and more symmetric form of these relations. We also establish an infinite tower of new identities between amplitudes in gauge theories.
Equivalence principle in scalar-tensor gravity
Dirk Puetzfeld; Yuri N. Obukhov
2015-05-06T23:59:59.000Z
We present a direct confirmation of the validity of the equivalence principle for unstructured test bodies in scalar tensor gravity. Our analysis is complementary to previous approaches and valid for a large class of scalar-tensor theories of gravitation. A covariant approach is used to derive the equations of motion in a systematic way and allows for the experimental test of scalar-tensor theories by means of extended test bodies.
Twisted covariant noncommutative self-dual gravity
Estrada-Jimenez, S.; Garcia-Compean, H.; Obregon, O.; Ramirez, C. [Centro de Estudios en Fisica y Matematicas Basicas y Aplicadas, Universidad Autonoma de Chiapas, Calle 4 Oriente Norte 1428, Tuxtla Gutierrez, Chiapas (Mexico); Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del IPN, P.O. Box 14-740, 07000 Mexico D.F. (Mexico); Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Monterrey, PIIT, Via del Conocimiento 201, Autopista nueva al Aeropuerto km 9.5, 66600, Apodaca Nuevo Leon (Mexico); Instituto de Fisica de la Universidad de Guanajuato, P.O. Box E-143, 37150, Leon Gto. (Mexico); Facultad de Ciencias Fisico Matematicas, Universidad Autonoma de Puebla, P.O. Box 1364, 72000, Puebla (Mexico)
2008-12-15T23:59:59.000Z
A twisted covariant formulation of noncommutative self-dual gravity is presented. The formulation for constructing twisted noncommutative Yang-Mills theories is used. It is shown that the noncommutative torsion is solved at any order of the {theta} expansion in terms of the tetrad and some extra fields of the theory. In the process the first order expansion in {theta} for the Plebanski action is explicitly obtained.
Emergent gravity and ether-drift experiments
M. Consoli; L. Pappalardo
2010-05-04T23:59:59.000Z
According to several authors, gravity might be a long-wavelength phenomenon emerging in some 'hydrodynamic limit' from the same physical, flat-space vacuum viewed as a form of superfluid medium. In this framework, light might propagate in an effective acoustic geometry and exhibit a tiny anisotropy that could be measurable in the present ether-drift experiments. By accepting this view of the vacuum, one should also consider the possibility of sizeable random fluctuations of the signal that reflect the stochastic nature of the underlying `quantum ether' and could be erroneously interpreted as instrumental noise. To test the present interpretation, we have extracted the mean amplitude of the signal from various experiments with different systematics, operating both at room temperature and in the cryogenic regime. They all give the same consistent value = O (10^{-15}) which is precisely the magnitude expected in an emergent-gravity approach, for an apparatus placed on the Earth's surface. Since physical implications could be substantial, it would be important to obtain more direct checks from the instantaneous raw data and, possibly, with new experimental set-ups operating in gravity-free environments.
Cosmology with Coupled Gravity and Dark Energy
Ti-Pei Li
2015-01-13T23:59:59.000Z
Dark energy is a fundamental constituent of our universe, its status in the cosmological field equation should be equivalent to that of gravity. Here we construct a dark energy and matter gravity coupling (DEMC) model of cosmology in a way that dark energy and gravity are introduced into the cosmological field equation in parallel with each other from the beginning. The DEMC universe possesses a composite symmetry from global Galileo invariance and local Lorentz invariance. The observed evolution of the universe expansion rate at redshift z>1 is in tension with the standard LCDM model, but can be well predicted by the DEMC model from measurements of only nearby epochs. The so far most precise measured expansion rate at high z is quite a bit slower than the expectations from LCDM, but remarkably consistent with that from DEMC. It is hoped that the DEMC scenario can also help to solve other existing challenges to cosmology: large scale anomalies in CMB maps and large structures up to about 10^3 Mpc of a quasar group. The DEMC universe is a well defined mechanical system. From measurements we can quantitatively evaluate its total rest energy, present absolute radius and expanding speed.
Quantum Gravito-Optics: A Light Route from Semiclassical Gravity to Quantum Gravity
Unnikrishnan, C S
2015-01-01T23:59:59.000Z
Quantum gravity remains an elusive theory, in spite of our thorough understanding of the quantum theory and the general theory of relativity separately, presumably due to the lack of any observational clues. We argue that the theory of quantum gravity has a strong constraining anchor in the sector of gravitational radiation ensuring reliable physical clues, albeit in a limited observable form. In particular, all types of gravitational waves expected to be observable in LIGO-like advanced detectors are fully quantum mechanical states of radiation. Exact equivalence of the full quantum gravity theory with the familiar semiclassical theory is ensured in the radiation sector, in most real situations where the relevant quantum operator functions are normal ordered, by the analogue of the optical equivalence theorem in quantum optics. We show that this is indeed the case for detection of the waves from a massive binary system, a single gravitational atom, that emits coherent radiation. The idea of quantum-gravitati...
Kristofer Davis, M. Andy Kass, and Yaoguo Li, Center for Gravity, Electrical and Magnetic Studies, Colorado
Cooling, Gravity and Geometry: Flow-driven Massive Core Formation
Fabian Heitsch; Lee Hartmann; Adrianne D. Slyz; Julien E. G. Devriendt; Andreas Burkert
2007-09-15T23:59:59.000Z
We study numerically the formation of molecular clouds in large-scale colliding flows including self-gravity. The models emphasize the competition between the effects of gravity on global and local scales in an isolated cloud. Global gravity builds up large-scale filaments, while local gravity -- triggered by a combination of strong thermal and dynamical instabilities -- causes cores to form. The dynamical instabilities give rise to a local focusing of the colliding flows, facilitating the rapid formation of massive protostellar cores of a few 100 M$_\\odot$. The forming clouds do not reach an equilibrium state, though the motions within the clouds appear comparable to ``virial''. The self-similar core mass distributions derived from models with and without self-gravity indicate that the core mass distribution is set very early on during the cloud formation process, predominantly by a combination of thermal and dynamical instabilities rather than by self-gravity.
Analysis of faults using gravity methods in Mason County, Texas
Milligan, Michael Glen
1992-01-01T23:59:59.000Z
Committee: Dr. D. A. Fahlquist Dr. B. Johnson The objective of this study is to determine the applicability of gravity profiling methods for determining the location and throw of a series of faults related to a structural graben in northern Mason County... profiles. For two faults with the best geologic control, the best-fit gravity models compared favorably with the the geologic model constructed by Randolph (1991) on the basis of surface mapping, structural control and well control. The gravity models...
New Agegraphic Dark Energy in $f(R)$ Gravity
M. R. Setare
2009-08-03T23:59:59.000Z
In this paper we study cosmological application of new agegraphic dark energy density in the $f(R)$ gravity framework. We employ the new agegraphic model of dark energy to obtain the equation of state for the new agegraphic energy density in spatially flat universe. Our calculation show, taking $nnew agegraphic dark energy model in flat universe in the modified gravity cosmology framework. Also we develop a reconstruction scheme for the modified gravity with $f(R)$ action.
Solar System experiments do not yet veto modified gravity models
Valerio Faraoni
2006-07-05T23:59:59.000Z
The dynamical equivalence between modified and scalar-tensor gravity theories is revisited and it is concluded that it breaks down in the limit to general relativity. A gauge-independent analysis of cosmological perturbations in both classes of theories lends independent support to this conclusion. As a consequence, the PPN formalism of scalar-tensor gravity and Solar System experiments do not veto modified gravity, as previously thought.
The f(R) Gravity Function of the Linde Quintessence
Sergei V. Ketov; Natsuki Watanabe
2014-10-20T23:59:59.000Z
We calculate the f(R) gravity function in the dual gravity description of the quintessence model with a quadratic (Linde) scalar potential and a positive cosmological constant. We find that in the large curvature regime relevant to chaotic inflation in early Universe, the dual f(R) gravity is well approximated by the (matter) loop-corrected Starobinsky inflationary model. In the small curvature regime relevant to dark energy in the present Universe, the f(R) gravity function reduces to the Einstein-Hilbert one with a positive cosmological constant.
Ground Gravity Survey At Lake City Hot Springs Area (Warpinski...
fault zones. The focus of Lake City Geothermal's current effort is on enhancing the site interpretation by re-evaluating the existing seismic data, conducting a detailed gravity...
Unification of Gravity and Electromagnetism II A Geometric Theory
Partha Ghose
2015-02-11T23:59:59.000Z
It is shown that unification of gravity and electromagnetism can be achieved using an affine non-symmetric connection $\\Gamma^\\lambda_{\\mu\
Summary of Session A6: Alternative Theories of Gravity
R. B. Mann
1998-03-13T23:59:59.000Z
This is a summary of the workshop A.6 on Alternative Theories of Gravity, prepared for the proceedings for the GR15 conference.
Quantized gauge-affine gravity in the superfiber bundle approach
A. Meziane; M. Tahiri
2005-11-10T23:59:59.000Z
The quantization of gauge-affine gravity within the superfiber bundle formalism is proposed. By introducing an even pseudotensorial 1-superform over a principal superfibre bundle with superconnection, we obtain the geometrical Becchi-Rouet-Stora-Tyutin (BRST) and anti-BRST transformations of the fields occurring in such a theory. Reducing the four-dimensional general affine group double-covering to the Poincare group double-covering we also find the BRST and anti-BRST transformations of the fields present in Einstein's gravity. Furthermore, we give a prescription leading to the construction of both BRST-invariant gauge-fixing action for gauge-affine gravity and Einstein's gravity.
Review of Lattice Supersymmetry and Gauge-Gravity Duality
Joseph, Anosh
2015-01-01T23:59:59.000Z
We review the status of recent investigations on validating the gauge-gravity duality conjecture through numerical simulations of strongly coupled maximally supersymmetric thermal gauge theories. In the simplest setting, the gauge-gravity duality connects systems of D0-branes and black hole geometries at finite temperature to maximally supersymmetric gauged quantum mechanics at the same temperature. Recent simulations show that non-perturbative gauge theory results give excellent agreement with the quantum gravity predictions, thus proving strong evidence for the validity of the duality conjecture and more insight into quantum black holes and gravity.
Parameterized post-Newtonian limit of Horndeski's gravity theory
Manuel Hohmann
2015-08-20T23:59:59.000Z
We present a recent result on the parameterized post-Newtonian (PPN) limit of Horndeski's gravity theory and its consistency with solar system observations.
Ground Gravity Survey At Under Steamboat Springs Area (Warpinski...
Under Steamboat Springs Area (Warpinski, Et Al., 2004) Exploration Activity Details Location Under Steamboat Springs Area Exploration Technique Ground Gravity Survey Activity Date...
Ground Gravity Survey At San Francisco Volcanic Field Area (Warpinski...
Francisco Volcanic Field Area (Warpinski, Et Al., 2004) Exploration Activity Details Location San Francisco Volcanic Field Area Exploration Technique Ground Gravity Survey Activity...
Costs of Imported Crude Oil by API Gravity
Gasoline and Diesel Fuel Update (EIA)
"Monthly Foreign Crude Oil Acquisition Report," July 1984 to present. 26. F.O.B. Costs of Imported Crude Oil by API Gravity 48 Energy Information Administration Petroleum...
Review of Lattice Supersymmetry and Gauge-Gravity Duality
Anosh Joseph
2015-09-04T23:59:59.000Z
We review the status of recent investigations on validating the gauge-gravity duality conjecture through numerical simulations of strongly coupled maximally supersymmetric thermal gauge theories. In the simplest setting, the gauge-gravity duality connects systems of D0-branes and black hole geometries at finite temperature to maximally supersymmetric gauged quantum mechanics at the same temperature. Recent simulations show that non-perturbative gauge theory results give excellent agreement with the quantum gravity predictions, thus proving strong evidence for the validity of the duality conjecture and more insight into quantum black holes and gravity.
Interfacial gravity currents. I. Mixing and entrainment B. R. Sutherland
Sutherland, Bruce
Interfacial gravity currents. I. Mixing and entrainment B. R. Sutherland Department of Mathematical energy are compared with theories that neglect mixing and entrainment processes. As the middle layer
Integration of Full Tensor Gravity and ZTEM Passive Low Frequency...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
and ZTEM Passive Low Frequency EM Instruments for Simultaneous Data Acquisition Integration of Full Tensor Gravity and ZTEM Passive Low Frequency EM Instruments for...
Strong and weak gravitational field in $R+?^4/R$ gravity
Kh. Saaidi; A. Vajdi; S. W. Rabiei; A. Aghamohammadi; H. Sheikhahmadi
2012-01-18T23:59:59.000Z
We introduce a new approach for investigating the weak field limit of vacuum field equations in $f(R)$ gravity and we find the weak field limit of $f(R)=R+\\mu ^4/R$ gravity. Furthermore, we study the strong gravity regime in $R+\\mu^{4}/R$ model of $f(R)$ gravity. We show the existence of strong gravitational field in vacuum for such model. We find out in the limit $\\mu\\rightarrow 0$, the weak field limit and the strong gravitational field can be regarded as a perturbed Schwarzschild metric.
Ground Gravity Survey At Blue Mountain Geothermal Area (Fairbank...
Ground Gravity Survey At Blue Mountain Geothermal Area (Fairbank Engineering Ltd, 2003) Jump to: navigation, search GEOTHERMAL ENERGYGeothermal Home Exploration Activity: Ground...
Dynamical stability of Minkowski space in higher order gravity
Petr V. Tretyakov
2015-05-19T23:59:59.000Z
We discuss the Minkowski stability problem in modified gravity by using dynamical system approach. The method to investigate dynamical stability of Minkowski space was proposed. This method was applied for some modified gravity theories, such as $f(R)$ gravity, $f(R)+\\alpha R\\Box R$ gravity and scalar-tensor gravity models with non-minimal kinetic coupling. It was shown that in the case of $f(R)$ gravity Minkowski solution asymptotically stable in ghost-free ($f'>0$) and tachyon-free ($f">0$) theories in expanding Universe with respect to isotropic and basic anisotropic perturbations. In the case of higher order gravity with $\\alpha R\\Box R$ correction conditions of Minkowski stability with respect to isotropic perturbations significantly different: $f'(0)0$. And in the case of scalar-tensor gravity with non-minimal kinetic coupling Minkowski solution asymptotically stable in expanding Universe with respect to isotropic perturbations of metric. Moreover the developed method may be used for finding additional restrictions on parameters of different modified gravity theories.
Ground Gravity Survey At Dixie Valley Geothermal Area (Allis...
2000) Exploration Activity Details Location Dixie Valley Geothermal Area Exploration Technique Ground Gravity Survey Activity Date 1999 - 2000 Usefulness not indicated DOE-funding...
Covariant Symplectic Structure and Conserved Charges of Topologically Massive Gravity
Caner Nazaroglu; Yavuz Nutku; Bayram Tekin
2011-06-07T23:59:59.000Z
We present the covariant symplectic structure of the Topologically Massive Gravity and find a compact expression for the conserved charges of generic spacetimes with Killing symmetries.
Exercise protocols during short-radius centrifugation for artificial gravity
Edmonds, Jessica Leigh
2008-01-01T23:59:59.000Z
Long-duration spaceflight results in severe physiological deconditioning, threatening the success of interplanetary travel. Exercise combined with artificial gravity provided by centrifugation may be the comprehensive ...
Effective Levi-Civita Dilaton theory from Metric Affine Dilaton Gravity
R. Scipioni
1999-05-25T23:59:59.000Z
We show how a Metric Affine theory of Dilaton gravity can be reduced to an effective Riemannian Dilaton gravity model. A simple generalization of the Obukhov-Tucker-Wang theorem to Dilaton gravity is then presented.
Quantum Gravito-Optics: A Light Route from Semiclassical Gravity to Quantum Gravity
C. S. Unnikrishnan; George T. Gillies
2015-08-03T23:59:59.000Z
Quantum gravity remains an elusive theory, in spite of our thorough understanding of the quantum theory and the general theory of relativity separately, presumably due to the lack of any observational clues. We argue that the theory of quantum gravity has a strong constraining anchor in the sector of gravitational radiation ensuring reliable physical clues, albeit in a limited observable form. In particular, all types of gravitational waves expected to be observable in LIGO-like advanced detectors are fully quantum mechanical states of radiation. Exact equivalence of the full quantum gravity theory with the familiar semiclassical theory is ensured in the radiation sector, in most real situations where the relevant quantum operator functions are normal ordered, by the analogue of the optical equivalence theorem in quantum optics. We show that this is indeed the case for detection of the waves from a massive binary system, a single gravitational atom, that emits coherent radiation. The idea of quantum-gravitational optics can assist in guiding along the fuzzy roads to quantum gravity.
Brane world cosmology with Gauss-Bonnet and induced gravity terms
Richard A. Brown
2007-01-15T23:59:59.000Z
In this thesis we investigate certain cosmological brane world models of the Randall-Sundrum type. The models are motivated by string theory but we focus on the phenomenology of the cosmology. Two models of specific interest are the Dvali-Gabadadze-Porrati (DGP, induced-gravity) model, where the brane action is modified, and the Gauss-Bonnet model where the bulk action is modified. Both of these modifications maybe motivated by string theory. We provide a brief review of Randall-Sundrum models and then consider the Kaluza-Klein modes on Minkowski and de Sitter branes, in both the two and one brane cases. The spectrum obtained for the de Sitter branes is a new result. We then consider a Friedmann-Robertson-Walker brane in order to investigate the cosmological dynamics on the brane. We present a brief discussion of the DGP and Gauss-Bonnet brane worlds. We then investigate the Gauss-Bonnet-Induced-Gravity (GBIG) model where the Gauss-Bonnet (GB) bulk term is combined with the induced-gravity (IG) brane term of the DGP model. We present a thorough investigation of cosmological dynamics, in particular focusing on GBIG models that behave like self-accelerating DGP models at late times but at early times show the remarkable feature of a finite-temperature Big Bang. We also discuss the constraints from observations, including ages and Big Bang nucleosynthesis.
Drag phenomena from holographic massive gravity
Matteo Baggioli; Daniel K. Brattan
2015-04-28T23:59:59.000Z
We consider the motion of point particles in a strongly coupled field theory with broken translation invariance. We obtain the energy and momentum loss rates and drag coefficients for a class of such particles by solving for the motion of classical strings in holographic massive gravity. At low temperatures compared to the graviton mass the behaviour of the string is controlled by the appearance of an exotic ground state with non-zero entropy at zero temperature. Additionally we find an upper bound on the diffusion constant for a collection of these particles which is saturated when the mass of the graviton goes to zero.
Drag phenomena from holographic massive gravity
Baggioli, Matteo
2015-01-01T23:59:59.000Z
We consider the motion of point particles in a strongly coupled field theory with broken translation invariance. We obtain the energy and momentum loss rates and drag coefficients for a class of such particles by solving for the motion of classical strings in holographic massive gravity. At low temperatures compared to the graviton mass the behaviour of the string is controlled by the appearance of an exotic ground state with non-zero entropy at zero temperature. Additionally we find an upper bound on the diffusion constant for a collection of these particles which is saturated when the mass of the graviton goes to zero.
Gravity can be neither classical nor quantized
Sabine Hossenfelder
2012-12-03T23:59:59.000Z
I argue that it is possible for a theory to be neither quantized nor classical. We should therefore give up the assumption that the fundamental theory which describes gravity at shortest distances must either be quantized, or quantization must emerge from a fundamentally classical theory. To illustrate my point I will discuss an example for a theory that is neither classical nor quantized, and argue that it has the potential to resolve the tensions between the quantum field theories of the standard model and general relativity.
Hall viscosity from gauge/gravity duality
Omid Saremi; Dam Thanh Son
2011-03-24T23:59:59.000Z
In (2+1)-dimensional systems with broken parity, there exists yet another transport coefficient, appearing at the same order as the shear viscosity in the hydrodynamic derivative expansion. In condensed matter physics, it is referred to as "Hall viscosity". We consider a simple holographic realization of a (2+1)-dimensional isotropic fluid with broken spatial parity. Using techniques of fluid/gravity correspondence, we uncover that the holographic fluid possesses a nonzero Hall viscosity, whose value only depends on the near-horizon region of the background. We also write down a Kubo's formula for the Hall viscosity. We confirm our results by directly computing the Hall viscosity using the formula.
A new quasidilaton theory of massive gravity
Shinji Mukohyama
2014-10-08T23:59:59.000Z
We present a new quasidilaton theory of Poincare invariant massive gravity, based on the recently proposed framework of matter coupling that makes it possible for the kinetic energy of the quasidilaton scalar to couple to both physical and fiducial metrics simultaneously. We find a scaling-type exact solution that expresses a self-accelerating de Sitter universe, and then analyze linear perturbations around it. It is shown that in a range of parameters all physical degrees of freedom have non-vanishing quadratic kinetic terms and are stable in the subhorizon limit, while the effective Newton's constant for the background is kept positive.
Static wormholes in vacuum for conformal gravity
Julio Oliva; David Tempo; Ricardo Troncoso
2009-07-07T23:59:59.000Z
A static spherically symmetric wormhole solution for conformal gravity in vacuum is found. The solution possesses a single integration constant which determines the size of the neck connecting two static homogeneous universes of constant spatial curvature. Time runs at different rates on each side of the neck, and depending on the value of the parameter, the wormhole can develop a cosmological horizon only at one side. It is shown that the wormholes correspond to the matching of different Einstein spacetimes by means of improper conformal transformations.
Null Energy Condition violations in bimetric gravity
Baccetti, Valentina; Visser, Matt
2012-01-01T23:59:59.000Z
We consider the effective stress-energy tensors for the foreground and background sectors in ghost-free bimetric gravity. By considering the symmetries of the theory, we show that the foreground and background null energy conditions (NECs) are strongly anti-correlated. In particular, the NECs can only be simultaneously fulfilled when they saturate, corresponding to foreground and background cosmological constants. In all other situations, either the foreground or the background is subject to a NEC-violating contribution to the total stress-energy.
Gamma Ray Burst Neutrinos Probing Quantum Gravity
M. C. Gonzalez-Garcia; F. Halzen
2006-11-28T23:59:59.000Z
Very high energy, short wavelength, neutrinos may interact with the space-time foam predicted by theories of quantum gravity. They would propagate like light through a crystal lattice and be delayed, with the delay depending on the energy. This will appear to the observer as a violation of Lorenz invariance. Back of the envelope calculations imply that observations of neutrinos produced by gamma ray bursts may reach Planck-scale sensitivity. We revisit the problem considering two essential complications: the imprecise timing of the neutrinos associated with their poorly understood production mechanism in the source and the indirect nature of their energy measurement made by high energy neutrino telescopes.
Dynamics of generalized Palatini theories of gravity
Vitagliano, Vincenzo; Liberati, Stefano [SISSA-International School for Advanced Studies, Via Bonomea 265, 34136 Trieste (Italy) and INFN sezione di Trieste, sezione di Trieste, via Valerio 2, 34127 Trieste (Italy); Sotiriou, Thomas P. [Department of Applied Mathematics and Theoretical Physics, Center for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom)
2010-10-15T23:59:59.000Z
It is known that in f(R) theories of gravity with an independent connection which can be both nonmetric and nonsymmetric, this connection can always be algebraically eliminated in favor of the metric and the matter fields, so long as it is not coupled to the matter explicitly. We show here that this is a special characteristic of f(R) actions, and it is not true for actions that include other curvature invariants. This contradicts some recent claims in the literature. We clarify the reasons for this contradiction.
Loop Quantum Gravity: An Inside View
Thomas Thiemann
2006-08-29T23:59:59.000Z
This is a (relatively) non -- technical summary of the status of the quantum dynamics in Loop Quantum Gravity (LQG). We explain in detail the historical evolution of the subject and why the results obtained so far are non -- trivial. The present text can be viewed in part as a response to an article by Nicolai, Peeters and Zamaklar [hep-th/0501114]. We also explain why certain no go conclusions drawn from a mathematically correct calculation in a recent paper by Helling et al [hep-th/0409182] are physically incorrect.
A high frequency resonance gravity gradiometer
Bagaev, S. N.; Kvashnin, N. L.; Skvortsov, M. N. [Laser Physics Institute SB RAS, Novosibirsc (Russian Federation); Bezrukov, L. B.; Krysanov, V. A. [Institute of Nuclear Physics RAS, Moscow (Russian Federation); Oreshkin, S. I.; Motylev, A. M.; Popov, S. M.; Samoilenko, A. A.; Yudin, I. S. [Lomonosov MSU, Sternberg Astronomical Institute, Moscow (Russian Federation); Rudenko, V. N. [Institute of Nuclear Physics RAS, Moscow (Russian Federation); Lomonosov MSU, Sternberg Astronomical Institute, Moscow (Russian Federation)
2014-06-15T23:59:59.000Z
A new setup OGRANthe large scale opto-acoustical gravitational detector is described. As distinguished from known gravitational bar detectors it uses the optical interferometrical readout for registering weak variations of gravity gradient at the kilohetz frequency region. At room temperature, its sensitivity is limited only by the bar Brownian noise at the bandwidth close to 100 Hz. It is destined for a search for rare eventsgravitational pulses coincident with signals of neutrino scintillator (BUST) in the deep underground of Baksan Neutrino Observatory of INR RAS.
Confronting Dilaton-exchange gravity with experiments
H. V. Klapdor-Kleingrothaus; H. Päs; U. Sarkar
2000-08-16T23:59:59.000Z
We study the experimental constraints on theories, where the equivalence principle is violated by dilaton-exchange contributions to the usual graviton-exchange gravity. We point out that in this case it is not possible to have any CPT violation and hence there is no constraint from the CPT violating measurements in the $K-$system. The most stringent bound is obtained from the $K_L - K_S$ mass difference. In contrast, neither neutrino oscillation experiments nor neutrinoless double beta decay imply significant constraints.
Seven-dimensional gravity with topological terms
Lue, H. [China Economics and Management Academy Central, University of Finance and Economics, Beijing 100081 (China); Institute for Advanced Study, Shenzhen University, Nanhai Ave 3688, Shenzhen 518060 (China); Pang Yi [Key Laboratory of Frontiers in Theoretical Physics Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China)
2010-04-15T23:59:59.000Z
We construct new seven-dimensional gravity by adding two topological terms to the Einstein-Hilbert action. For a certain choice of the coupling constants, these terms exist naturally in seven-dimensional gauged supergravity from the S{sup 4} reduction of eleven-dimensional supergravity with the R{sup 4} corrections. We derive the full set of the equations of motion. We find that the static spherically-symmetric black holes are unmodified by the topological terms. We obtain squashed AdS{sub 7}, and also squashed seven spheres and Q{sup 111} spaces in Euclidean signature.
Anisotropic higher derivative gravity and inflationary universe
W. F. Kao
2006-05-21T23:59:59.000Z
Stability analysis of the Kantowski-Sachs type universe in pure higher derivative gravity theory is studied in details. The non-redundant generalized Friedmann equation of the system is derived by introducing a reduced one dimensional generalized KS type action. This method greatly reduces the labor in deriving field equations of any complicate models. Existence and stability of inflationary solution in the presence of higher derivative terms are also studied in details. Implications to the choice of physical theories are discussed in details in this paper.
Inflationary Universe in Higher Derivative Induced Gravity
W. F. Kao
2000-06-27T23:59:59.000Z
In an induced-gravity model, the stability condition of an inflationary slow-rollover solution is shown to be $\\phi_0 \\partial_{\\phi_0}V(\\phi_0)=4V(\\phi_0)$. The presence of higher derivative terms will, however, act against the stability of this expanding solution unless further constraints on the field parameters are imposed. We find that these models will acquire a non-vanishing cosmological constant at the end of inflation. Some models are analyzed for their implication to the early universe.
Energy Conditions in $f(G)$ Modified Gravity with Non-minimal Coupling to Matter
A. Banijamali; B. Fazlpour; M. R. Setare
2011-11-15T23:59:59.000Z
In this paper we study a model of modified gravity with non-minimal coupling between a general function of the Gauss-Bonnet invariant, $f(G)$, and matter Lagrangian from the point of view of the energy conditions. Such model has been introduced in Ref. [21] for description of early inflation and late-time cosmic acceleration. We present the suitable energy conditions for the above mentioned model and then, we use the estimated values of the Hubble, deceleration and jerk parameters to apply the obtained energy conditions to the specific class of modified Gauss-Bonnet models.
Moho topography beneath the Corinth Rift area (Greece) from inversion of gravity data
Demouchy, Sylvie
Moho topography beneath the Corinth Rift area (Greece) from inversion of gravity data C. Tiberi,1 to Miocene lithospheric instabilities. Key words: boudinage, continental rifts, gravity inversion, Greece
Synoptic Responses to Mountain Gravity Waves Encountering Directional Critical Levels
Lott, Francois
Synoptic Responses to Mountain Gravity Waves Encountering Directional Critical Levels ARMEL MARTIN the synoptic response to mountain gravity waves (GWs) absorbed at directional critical levels. The model in the midtroposphere. First, the authors consider the case of an idealized mountain range such that the orographic
Cosmological evolutions of $F(R)$ nonlinear massive gravity
De-Jun Wu
2014-03-24T23:59:59.000Z
Recently a new extended nonlinear massive gravity model has been proposed which includes the $F(R)$ modifications to dRGT model.We follow the $F(R)$ nonlinear massive gravity and study its implications on cosmological evolutions. We derive the critical points of the cosmic system and study the corresponding kinetics by performing the phase-plane analysis.
On coupling NEC-violating matter to gravity
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Chatterjee, Saugata; Parikh, Maulik; van der Schaar, Jan Pieter
2015-05-01T23:59:59.000Z
We show that effective theories of matter that classically violate the null energy condition cannot be minimally coupled to Einstein gravity without being inconsistent with both string theory and black hole thermodynamics. We argue however that they could still be either non-minimally coupled or coupled to higher-curvature theories of gravity.
18 Maple Syrup Digest HIGH VACUUM IN GRAVITY TUBING
Hayden, Nancy J.
where elec- tricity is not available, time needed for maintenance of a pump and extractor gravity tubing, or tubing without the use of a pump, to be a poor substitute for a modern system with a pump, extractor, and the latest tubing arrangement. Sap yields from gravity systems are often half
Gravity Field and Internal Structure of Mercury from MESSENGER
Zuber, Maria
,5 Mark E. Perry,11 David D. Rowlands,5 Sander Goossens,12 James W. Head,13 Anthony H. Taylor14 RadioGravity Field and Internal Structure of Mercury from MESSENGER David E. Smith,1 Maria T. Zuber,1 tracking of the MESSENGER spacecraft has provided a model of Mercury's gravity field. In the northern
Motion in alternative theories of gravity
Gilles Esposito-Farese
2009-05-15T23:59:59.000Z
Although general relativity (GR) passes all present experimental tests with flying colors, it remains important to study alternative theories of gravity for several theoretical and phenomenological reasons that we recall in these lecture notes. The various possible ways of modifying GR are presented, and we notably show that the motion of massive bodies may be changed even if one assumes that matter is minimally coupled to the metric as in GR. This is illustrated with the particular case of scalar-tensor theories of gravity, whose Fokker action is discussed, and we also mention the consequences of the no-hair theorem on the motion of black holes. The finite size of the bodies modifies their motion with respect to pointlike particles, and we give a simple argument showing that the corresponding effects are generically much larger in alternative theories than in GR. We also discuss possible modifications of Newtonian dynamics (MOND) at large distances, which have been proposed to avoid the dark matter hypothesis. We underline that all the previous classes of alternatives to GR may a priori be used to predict such a phenomenology, but that they generically involve several theoretical and experimental difficulties.
Canonical Quantum Gravity on Noncommutative Spacetime
Martin Kober
2014-09-04T23:59:59.000Z
In this paper canonical quantum gravity on noncommutative space-time is considered. The corresponding generalized classical theory is formulated by using the moyal star product, which enables the representation of the field quantities depending on noncommuting coordinates by generalized quantities depending on usual coordinates. But not only the classical theory has to be generalized in analogy to other field theories. Besides, the necessity arises to replace the commutator between the gravitational field operator and its canonical conjugated quantity by a corresponding generalized expression on noncommutative space-time. Accordingly the transition to the quantum theory has also to be performed in a generalized way and leads to extended representations of the quantum theoretical operators. If the generalized representations of the operators are inserted to the generalized constraints, one obtains the corresponding generalized quantum constraints including the Hamiltonian constraint as dynamical constraint. After considering quantum geometrodynamics under incorporation of a coupling to matter fields, the theory is transferred to the Ashtekar formalism. The holonomy representation of the gravitational field as it is used in loop quantum gravity opens the possibility to calculate the corresponding generalized area operator.
New ground state for quantum gravity
Joao Magueijo; Laura Bethke
2012-07-03T23:59:59.000Z
In this paper we conjecture the existence of a new "ground" state in quantum gravity, supplying a wave function for the inflationary Universe. We present its explicit perturbative expression in the connection representation, exhibiting the associated inner product. The state is chiral, dependent on the Immirzi parameter, and is the vacuum of a second quantized theory of graviton particles. We identify the physical and unphysical Hilbert sub-spaces. We then contrast this state with the perturbed Kodama state and explain why the latter can never describe gravitons in a de Sitter background. Instead, it describes self-dual excitations, which are composites of the positive frequencies of the right-handed graviton and the negative frequencies of the left-handed graviton. These excitations are shown to be unphysical under the inner product we have identified. Our rejection of the Kodama state has a moral tale to it: the semi-classical limit of quantum gravity can be the wrong path for making contact with reality (which may sometimes be perturbative but nonetheless fully quantum). Our results point towards a non-perturbative extension, and we present some conjectures on the nature of this hypothetical state.
Dipole gravity waves from unbound quadrupoles
Felber, Franklin
2010-01-01T23:59:59.000Z
Dipole gravitational disturbances from gravitationally unbound mass quadrupoles propagate to the radiation zone with signal strength at least of quadrupole order if the quadrupoles are nonrelativistic, and of dipole order if relativistic. Angular distributions of parallel-polarized and transverse-polarized dipole power in the radiation zone are calculated for simple unbound quadrupoles, like a linear-oscillator/stress-wave pair and a particle storage ring. Laboratory tests of general relativity through measurements of dipole gravity waves in the source region are proposed. A NASA G2 flywheel module with a modified rotor can produce a post-Newtonian dc bias signal at a gradiometer up to 1 mE. At peak luminosity, the repulsive dipole impulses of proton bunches at the LHC can produce an rms velocity of a high-Q detector surface up to 4 micron/s. Far outside the source region, Newtonian lunar dipole gravity waves can produce a 1-cm displacement signal at LISA. Dipole signal strengths of astrophysical events invol...
Dipole gravity waves from unbound quadrupoles
Franklin Felber
2010-06-10T23:59:59.000Z
Dipole gravitational disturbances from gravitationally unbound mass quadrupoles propagate to the radiation zone with signal strength at least of quadrupole order if the quadrupoles are nonrelativistic, and of dipole order if relativistic. Angular distributions of parallel-polarized and transverse-polarized dipole power in the radiation zone are calculated for simple unbound quadrupoles, like a linear-oscillator/stress-wave pair and a particle storage ring. Laboratory tests of general relativity through measurements of dipole gravity waves in the source region are proposed. A NASA G2 flywheel module with a modified rotor can produce a post-Newtonian dc bias signal at a gradiometer up to 1 mE. At peak luminosity, the repulsive dipole impulses of proton bunches at the LHC can produce an rms velocity of a high-Q detector surface up to 4 micron/s. Far outside the source region, Newtonian lunar dipole gravity waves can produce a 1-cm displacement signal at LISA. Dipole signal strengths of astrophysical events involving unbound quadrupoles, like near collisions and neutron star kicks in core-collapse supernovae, are estimated.
Vacuum energy: quantum hydrodynamics vs quantum gravity
G. E. Volovik
2005-09-09T23:59:59.000Z
We compare quantum hydrodynamics and quantum gravity. They share many common features. In particular, both have quadratic divergences, and both lead to the problem of the vacuum energy, which in the quantum gravity transforms to the cosmological constant problem. We show that in quantum liquids the vacuum energy density is not determined by the quantum zero-point energy of the phonon modes. The energy density of the vacuum is much smaller and is determined by the classical macroscopic parameters of the liquid including the radius of the liquid droplet. In the same manner the cosmological constant is not determined by the zero-point energy of quantum fields. It is much smaller and is determined by the classical macroscopic parameters of the Universe dynamics: the Hubble radius, the Newton constant and the energy density of matter. The same may hold for the Higgs mass problem: the quadratically divergent quantum correction to the Higgs potential mass term is also cancelled by the microscopic (trans-Planckian) degrees of freedom due to thermodynamic stability of the whole quantum vacuum.
Hill, D.W.; Sande, J.J. [Shell Western E& P Inc., Bakersfield, CA (United States); Doe, P.H. [Shell Development Co., Houston, TX (United States)
1995-04-01T23:59:59.000Z
Understanding oil gravity distribution in the Belridge Diatomite has led to economic infill development and specific enhanced recovery methods for targeted oil properties. To date more than 100 wells have provided samples used to determining vertical and areal distribution of oil gravity in the field. Detailed geochemical analyses were also conducted on many of the oil samples to establish different oil types, relative maturities, and to identify transformed oils. The geochemical analysis also helped identify source rock expulsion temperatures and depositional environments. The data suggests that the Belridge diatomite has been charged by a single hydrocarbon source rock type and was generated over a relatively wide range of temperatures. Map and statistical data support two distinct oil segregation processes occurring post expulsion. Normal gravity segregation within depositional cycles of diatomite have caused lightest oils to migrate to the crests of individual cycle structures. Some data suggests a loss of the light end oils in the uppermost cycles to the Tulare Formation above, or through early biodegradation. Structural rotation post early oil expulsion has also left older, heavier oils concentrated on the east flank of the structure. With the addition of other samples from the south central San Joaquin area, we have been able to tie the Belridge diatomite hydrocarbon charge into a regional framework. We have also enhanced our ability to predict oil gravity and well primary recovery by unraveling some key components of the diatomite oil source and migration history.
Mesa Top Photovoltaic Array SyStem SpecificationS
Mesa Top Photovoltaic Array SyStem SpecificationS System size: 750 kW (DC, estimated) Characteristics: Single axis tracker photovoltaics, ground mounted Annual output: 1,200 MWh Location: Top of South
Qiang, Li-E
2015-01-01T23:59:59.000Z
High precision Superconductivity Gravity Gradiometers (SGG) are powerful tools for relativistic experiments. In this paper, we work out the tidal signals in non-dynamical Chern-Simons modified gravity, which could be measured by orbiting SGGs around Earth. We find that, with proper orientations of multi-axes SGGs, the tidal signals from the Chern-Simons modification can be isolated in the combined data of different axes. Furthermore, for three-axes SGGs, such combined data is the trace of the total tidal matrix, which is invariant under the rotations of SGG axes and thus free from axis pointing errors. Following nearly circular orbits, the tests of the parity-violating Chern-Simons modification and the measurements of the gravitomagnetic sector in parity-conserving metric theories can be carried out independently in the same time. A first step analysis on noise sources is also included.
Li-E Qiang; Peng Xu
2015-02-16T23:59:59.000Z
High precision Superconductivity Gravity Gradiometers (SGG) are powerful tools for relativistic experiments. In this paper, we work out the tidal signals in non-dynamical Chern-Simons modified gravity, which could be measured by orbiting SGGs around Earth. We find that, with proper orientations of multi-axes SGGs, the tidal signals from the Chern-Simons modification can be isolated in the combined data of different axes. Furthermore, for three-axes SGGs, such combined data is the trace of the total tidal matrix, which is invariant under the rotations of SGG axes and thus free from axis pointing errors. Following nearly circular orbits, the tests of the parity-violating Chern-Simons modification and the measurements of the gravitomagnetic sector in parity-conserving metric theories can be carried out independently in the same time. A first step analysis on noise sources is also included.
Specification No. 203-HJT-9004 R0 Specification for the
McDonald, Kirk
Specification No. 203-HJT-9004 R0 Specification for the MERIT Mercury-Jet Experiment Titanium TITANIUM TARGET MODULE COMPONENTS Prepared by: V.B. Graves (Oak Ridge National Laboratory) P. T. Spampinato.S. DEPARTMENT OF ENERGY April 10, 2006 #12;Specification for Ti Alloy Components MERIT High Power Mercury
Bending of light in conformal Weyl gravity
Sultana, Joseph; Kazanas, Demosthenes [Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States) and Department of Mathematics, University of Malta, Msida (Malta); Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, Maryland 20771 (United States)
2010-06-15T23:59:59.000Z
We reexamine the bending of light issue associated with the metric of the static, spherically symmetric solution of Weyl gravity discovered by Mannheim and Kazanas (1989). To this end we employ the procedure used recently by Rindler and Ishak to obtain the bending angle of light by a centrally concentrated spherically symmetric matter distribution in a Schwarzschild-de Sitter background. In earlier studies the term {gamma}r in the metric led to the paradoxical result of a bending angle proportional to the photon impact parameter, when using the usual formalism appropriate to asymptotically flat space-times. However, employing the approach of light bending of Rindler and Ishak we show that the effects of this term are in fact insignificant, with the discrepancy between the two procedures attributed to the definition of the bending angle between the asymptotically flat and nonflat spaces.
What is Dynamics in Quantum Gravity?
Malkiewicz, Przemyslaw
2015-01-01T23:59:59.000Z
Dynamics of general relativistic systems is given with respect to internal clocks. We investigate the extent to which the choice of internal clock in quantum description of the gravitational field determines the quantum dynamics. We develop our method by making use of the Hamilton-Jacobi theory, which is extended to include time coordinate transformations. Next, we apply our method to a quantum model of the flat Friedmann universe and compute some clock-induced deviations to semiclassical phase space portrait. Within a fixed quantization we find the abundance of possible semiclassical extensions to general relativity by switching between clocks. It follows that quantities like minimal volume, maximal curvature and even a number of quantum bounces, often used to describe quantum effects in gravity, are ill-defined.
What is Dynamics in Quantum Gravity?
Przemyslaw Malkiewicz
2015-05-18T23:59:59.000Z
Dynamics of general relativistic systems is given with respect to internal clocks. We investigate the extent to which the choice of internal clock in quantum description of the gravitational field determines the quantum dynamics. We develop our method by making use of the Hamilton-Jacobi theory, which is extended to include time coordinate transformations. Next, we apply our method to a quantum model of the flat Friedmann universe and compute some clock-induced deviations to semiclassical phase space portrait. Within a fixed quantization we find the abundance of possible semiclassical extensions to general relativity by switching between clocks. It follows that quantities like minimal volume, maximal curvature and even a number of quantum bounces, often used to describe quantum effects in gravity, are ill-defined.
Phenomenologically viable Lorentz-violating quantum gravity
Sotiriou, Thomas; Weinfurtner, Silke
2009-01-01T23:59:59.000Z
Horava's "Lifschitz point gravity" has many desirable features, but in its original incarnation one is forced to accept a non-zero cosmological constant of the wrong sign to be compatible with observation. We develop an extension of Horava's model that abandons "detailed balance", and in 3+1 dimensions exhibit all five marginal (renormalizable) and four relevant (super-renormalizable) operators, as determined by power counting. We also consider the classical limit of this theory, evaluate the Hamiltonian and super-momentum constraints, and extract the classical equations of motion in a form similar to the ADM formulation of general relativity. This puts the model in a framework amenable to developing detailed precision tests.
Nonsingular cosmology from evolutionary quantum gravity
Francesco Cianfrani; Giovanni Montani; Fabrizio Pittorino
2014-10-30T23:59:59.000Z
We provide a cosmological implementation of the evolutionary quantum gravity, describing an isotropic Universe, in the presence of a negative cosmological constant and a massive (preinflationary) scalar field. We demonstrate that the considered Universe has a nonsingular quantum behavior, associated to a primordial bounce, whose ground state has a high occupation number. Furthermore, in such a vacuum state, the super-Hamiltonian eigenvalue is negative, corresponding to a positive emerging dust energy density. The regularization of the model is performed via a polymer quantum approach to the Universe scale factor and the proper classical limit is then recovered, in agreement with a preinflationary state of the Universe. Since the dust energy density is redshifted by the Universe deSitter phase and the cosmological constant does not enter the ground state eigenvalue, we get a late-time cosmology, compatible with the present observations, endowed with a turning point in the far future.
Quantum Mechanics, Gravity, and the Multiverse
Yasunori Nomura
2012-07-30T23:59:59.000Z
The discovery of accelerating expansion of the universe has led us to take the dramatic view that our universe may be one of the many universes in which low energy physical laws take different forms: the multiverse. I explain why/how this view is supported both observationally and theoretically, especially by string theory and eternal inflation. I then describe how quantum mechanics plays a crucial role in understanding the multiverse, even at the largest distance scales. The resulting picture leads to a revolutionary change of our view of spacetime and gravity, and completely unifies the paradigm of the eternally inflating multiverse with the many worlds interpretation of quantum mechanics. The picture also provides a solution to a long-standing problem in eternal inflation, called the measure problem, which I briefly describe.
Mixing lengths scaling in a gravity flow
Ecke, Robert E [Los Alamos National Laboratory; Rivera, Micheal [Los Alamos National Laboratory; Chen, Jun [Los Alamos National Laboratory; Ecke, Robert E [Los Alamos National Laboratory
2009-01-01T23:59:59.000Z
We present an experimental study of the mixing processes in a gravity current. The turbulent transport of momentum and buoyancy can be described in a very direct and compact form by a Prandtl mixing length model [1]: the turbulent vertical fluxes of momentum and buoyancy are found to scale quadraticatly with the vertical mean gradients of velocity and density. The scaling coefficient is the square of the mixing length, approximately constant over the mixing zone of the stratified shear layer. We show in this paper how, in different flow configurations, this length can be related to the shear length of the flow {radical}({var_epsilon}/{partial_derivative}{sub z}u{sup 3}).
Kinetic Gravity Braiding and axion inflation
Debaprasad Maity
2013-03-11T23:59:59.000Z
We constructed a new class of inflationary model with the higher derivative axion field which obeys constant shift symmetry. In the usual axion (natural) inflation, the axion decay constant is predicted to be in the super-Planckian regime which is believed to be incompatible with an effective field theory framework. With a novel mechanism originating from a higher derivative kinetic gravity braiding (KGB) of an axion field we found that there exist a huge parameter regime in our model where axion decay constant could be naturally sub-Planckian. Thanks to the KGB which effectively reduces the Planck constant. This effectively reduced Planck scale provides us the mechanism of further lowering down the speed of an axion field rolling down its potential without introducing super-Planckian axion decay constant. We also find that with that wide range of parameter values, our model induces almost scale invariant power spectrum as observed in CMB experiments.
A length operator for canonical quantum gravity
T. Thiemann
1996-06-29T23:59:59.000Z
We construct an operator that measures the length of a curve in four-dimensional Lorentzian vacuum quantum gravity. We work in a representation in which a $SU(2)$ connection is diagonal and it is therefore surprising that the operator obtained after regularization is densely defined, does not suffer from factor ordering singularities and does not require any renormalization. We show that the length operator admits self-adjoint extensions and compute part of its spectrum which like its companions, the volume and area operators already constructed in the literature, is purely discrete and roughly is quantized in units of the Planck length. The length operator contains full and direct information about all the components of the metric tensor which faciliates the construction of a new type of weave states which approximate a given classical 3-geometry.
Bi-metric Gravity and "Dark Matter"
I. T. Drummond
2000-08-18T23:59:59.000Z
We present a bi-metric theory of gravity containing a length scale of galactic size. For distances less than this scale the theory satisfies the standard tests of General Relativity. For distances greater than this scale the theory yields an effective gravitational constant much larger than the locally observed value of Newton's constant. The transition from one regime to the other through the galactic scale can explain the observed rotation curves of galaxies and hence the effects normally attributed to the presence of dark matter. Phenomena on an extragalactic scale such as galactic clusters and the expansion of the universe are controlled by the enhanced gravitational coupling. This provides an explanation of the missing matter normally invoked to account for the observed value of Hubble's constant in relation to observed matter.
Black Hole Thermodynamics in Modified Gravity
Jonas R. Mureika; John W. Moffat; Mir Faizal
2015-03-03T23:59:59.000Z
We analyze the thermodynamics of a non-rotating and rotating black hole in a modified theory of gravity that includes scalar and vector modifications to general relativity, which results in a modified gravitational constant $G = G_N(1+\\alpha)$ and a new gravitational charge $Q = \\sqrt{\\alpha G_N}M$. The influence of the parameter $\\alpha$ alters the non-rotating black hole's lifetime, temperature and entropy profiles from the standard Schwarzschild case. The thermodynamics of a rotating black hole is analyzed and it is shown to possess stable, cold remnants. The thermodynamic properties of a vacuum solution regular at $r=0$ are investigated and the solution without a horizon called a "gray hole" is not expected to possess an information loss problem.
Solar system tests of Ho?ava-Lifshitz gravity
Tiberiu Harko; Zoltan Kovács; Francisco S. N. Lobo
2010-10-28T23:59:59.000Z
Recently, a renormalizable gravity theory with higher spatial derivatives in four dimensions was proposed by Ho\\v{r}ava. The theory reduces to Einstein gravity with a non-vanishing cosmological constant in IR, but it has improved UV behaviors. The spherically symmetric black hole solutions for an arbitrary cosmological constant, which represent the generalization of the standard Schwarzschild-(A)dS solution, has also been obtained for the Ho\\v{r}ava-Lifshitz theory. The exact asymptotically flat Schwarzschild type solution of the gravitational field equations in Ho\\v{r}ava gravity contains a quadratic increasing term, as well as the square root of a fourth order polynomial in the radial coordinate, and it depends on one arbitrary integration constant. The IR modified Ho\\v{r}ava gravity seems to be consistent with the current observational data, but in order to test its viability more observational constraints are necessary. In the present paper we consider the possibility of observationally testing Ho\\v{r}ava gravity at the scale of the Solar System, by considering the classical tests of general relativity (perihelion precession of the planet Mercury, deflection of light by the Sun and the radar echo delay) for the spherically symmetric black hole solution of Ho\\v{r}ava-Lifshitz gravity. All these gravitational effects can be fully explained in the framework of the vacuum solution of the gravity. Moreover, the study of the classical general relativistic tests also constrain the free parameter of the solution.
Goedel-type universes in f(R) gravity
Reboucas, M. J. [Centro Brasileiro de Pesquisas Fisicas, Rua Dr. Xavier Sigaud 150, 22290-180 Rio de Janeiro-RJ (Brazil); Santos, J. [Universidade Federal do Rio G. do Norte, Departamento de Fisica, 59072-970 Natal-RN (Brazil)
2009-09-15T23:59:59.000Z
The f(R) gravity theories provide an alternative way to explain the current cosmic acceleration without a dark energy matter component. If gravity is governed by a f(R) theory, a number of issues should be reexamined in this framework, including the violation of causality problem on nonlocal scale. We examine the question as to whether the f(R) gravity theories permit space-times in which the causality is violated. We show that the field equations of these f(R) gravity theories do not exclude solutions with breakdown of causality for a physically well-motivated perfect-fluid matter content. We demonstrate that every perfect-fluid Goedel-type solution of a generic f(R) gravity satisfying the condition df/dR>0 is necessarily isometric to the Goedel geometry, and therefore presents violation of causality. This result extends a theorem on Goedel-type models, which has been established in the context of general relativity. We also derive an expression for the critical radius r{sub c} (beyond which the causality is violated) for an arbitrary f(R) theory, making apparent that the violation of causality depends on both the f(R) gravity theory and the matter content. As an illustration, we concretely take a recent f(R) gravity theory that is free from singularities of the Ricci scalar and is cosmologically viable, and show that this theory accommodates noncausal as well as causal Goedel-type solutions.
The dynamics of metric-affine gravity
Vitagliano, Vincenzo, E-mail: vitaglia@sissa.it [SISSA-International School for Advanced Studies, Via Bonomea 265, 34136 Trieste (Italy); INFN, Sez. di Trieste, Via Valerio 2, 34127 Trieste (Italy); Sotiriou, Thomas P., E-mail: T.Sotiriou@damtp.cam.ac.uk [Department of Applied Mathematics and Theoretical Physics, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge, CB3 0WA (United Kingdom); Liberati, Stefano, E-mail: liberati@sissa.it [SISSA-International School for Advanced Studies, Via Bonomea 265, 34136 Trieste (Italy); INFN, Sez. di Trieste, Via Valerio 2, 34127 Trieste (Italy)
2011-05-15T23:59:59.000Z
Highlights: > The role and the dynamics of the connection in metric-affine theories is explored. > The most general second order action does not lead to a dynamical connection. > Including higher order invariants excites new degrees of freedom in the connection. > f(R) actions are also discussed and shown to be a non- representative class. - Abstract: Metric-affine theories of gravity provide an interesting alternative to general relativity: in such an approach, the metric and the affine (not necessarily symmetric) connection are independent quantities. Furthermore, the action should include covariant derivatives of the matter fields, with the covariant derivative naturally defined using the independent connection. As a result, in metric-affine theories a direct coupling involving matter and connection is also present. The role and the dynamics of the connection in such theories is explored. We employ power counting in order to construct the action and search for the minimal requirements it should satisfy for the connection to be dynamical. We find that for the most general action containing lower order invariants of the curvature and the torsion the independent connection does not carry any dynamics. It actually reduces to the role of an auxiliary field and can be completely eliminated algebraically in favour of the metric and the matter field, introducing extra interactions with respect to general relativity. However, we also show that including higher order terms in the action radically changes this picture and excites new degrees of freedom in the connection, making it (or parts of it) dynamical. Constructing actions that constitute exceptions to this rule requires significant fine tuned and/or extra a priori constraints on the connection. We also consider f(R) actions as a particular example in order to show that they constitute a distinct class of metric-affine theories with special properties, and as such they cannot be used as representative toy theories to study the properties of metric-affine gravity.
Zeinab Sherkatghanad; Behrouz Mirza; Zahra Mirzaeyan; Seyed Ali Hosseini Mansoori
2014-12-16T23:59:59.000Z
We consider the critical behaviors and phase transitions of Gauss Bonnet-Born Infeld-AdS black holes (GB-BI-AdS) for $d=5,6$ and the extended phase space. We assume the cosmological constant, $\\Lambda$, the coupling coefficient $\\alpha$, and the BI parameter $\\beta$ to be thermodynamic pressures of the system. Having made these assumptions, the critical behaviors are then studied in the two canonical and grand canonical ensembles. We find "reentrant and triple point phase transitions" (RPT-TP) and "multiple reentrant phase transitions" (multiple RPT) with increasing pressure of the system for specific values of the coupling coefficient $\\alpha$ in the canonical ensemble. Also, we observe a reentrant phase transition (RPT) of GB-BI-AdS black holes in the grand canonical ensemble and for $d=6$. These calculations are then expanded to the critical behavior of Born-Infeld-AdS (BI-AdS) black holes in the third order of Lovelock gravity and in the grand canonical ensemble to find a Van der Waals behavior for $d=7$ and a reentrant phase transition for $d=8$ for specific values of potential $\\phi$ in the grand canonical ensemble. Furthermore, we obtain a similar behavior for the limit of $\\beta \\to \\infty$, i.e charged-AdS black holes in the third order of the Lovelock gravity. Thus, it is shown that the critical behaviors of these black holes are independent of the parameter $\\beta$ in the grand canonical ensemble.
Particles on a Circle in Canonical Lineal Gravity
R. B. Mann
2001-05-02T23:59:59.000Z
A description of the canonical formulation of lineal gravity minimally coupled to N point particles in a circular topology is given. The Hamiltonian is found to be equal to the time-rate of change of the extrinsic curvature multiplied by the proper circumference of the circle. Exact solutions for pure gravity and for gravity coupled to a single particle are obtained. The presence of a single particle significantly modifies the spacetime evolution by either slowing down or reversing the cosmological expansion of the circle, depending upon the choice of parameters.
Emergent noncommutative gravity from a consistent deformation of gauge theory
Cortese, Ignacio; Garcia, J Antonio [Departamento de Fisica de Altas Energias, Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, Apartado Postal 70-543, Mexico D. F. 04510 (Mexico)
2010-05-15T23:59:59.000Z
Starting from a standard noncommutative gauge theory and using the Seiberg-Witten map, we propose a new version of a noncommutative gravity. We use consistent deformation theory starting from a free gauge action and gauging a killing symmetry of the background metric to construct a deformation of the gauge theory that we can relate with gravity. The result of this consistent deformation of the gauge theory is nonpolynomial in A{sub {mu}.} From here we can construct a version of noncommutative gravity that is simpler than previous attempts. Our proposal is consistent and is not plagued with the problems of other approaches like twist symmetries or gauging other groups.
Flat space (higher spin) gravity with chemical potentials
Michael Gary; Daniel Grumiller; Max Riegler; Jan Rosseel
2014-11-24T23:59:59.000Z
We introduce flat space spin-3 gravity in the presence of chemical potentials and discuss some applications to flat space cosmology solutions, their entropy, free energy and flat space orbifold singularity resolution. Our results include flat space Einstein gravity with chemical potentials as special case. We discover novel types of phase transitions between flat space cosmologies with spin-3 hair and show that the branch that continuously connects to spin-2 gravity becomes thermodynamically unstable for sufficiently large temperature or spin-3 chemical potential.
Emergent gravity/Non-linear U(1) gauge theory correspondence
Supriya Kar; K. Priyabrat Pandey; Abhishek K. Singh; Sunita Singh
2010-02-21T23:59:59.000Z
Kaluza-Klein gravity is revisted, with renewed interest, in a type IIB string theory on $S^1\\times K3$. The irreducible curvature tensors are worked out in the, T-dual, emergent gravity in 4D to yield a non-linear U(1) gauge theory. Interestingly, the T-duality may be seen to describe an open/closed string duality at a self-dual string coupling. The obtained deformation in $AdS_5$ black hole is analyzed to introduce the notion of temperature in the emergent gravity underlying the recent idea of entropic force.
The emission of Gamma Ray Bursts as a test-bed for modified gravity
Salvatore Capozziello; Gaetano Lambiase
2015-04-15T23:59:59.000Z
The extreme physical conditions of Gamma Ray Bursts can constitute a useful observational laboratory to test theories of gravity where very high curvature regimes are involved. Here we propose a sort of curvature engine capable, in principle, of explaining the huge energy emission of Gamma Ray Bursts. Specifically, we investigate the emission of radiation by charged particles non-minimally coupled to the gravitational background where higher order curvature invariants are present. The coupling gives rise to an additional force inducing a non-geodesics motion of particles. This fact allows a strong emission of radiation by gravitationally accelerated particles. As we will show with some specific model, the energy emission is of the same order of magnitude of that characterizing the Gamma Ray Burst physics. Alternatively, strong curvature regimes can be considered as a natural mechanism for the generation of highly energetic astrophysical events.
The emission of Gamma Ray Bursts as a test-bed for modified gravity
Capozziello, Salvatore
2015-01-01T23:59:59.000Z
The extreme physical conditions of Gamma Ray Bursts can constitute a useful observational laboratory to test theories of gravity where very high curvature regimes are involved. Here we propose a sort of curvature engine capable, in principle, of explaining the huge energy emission of Gamma Ray Bursts. Specifically, we investigate the emission of radiation by charged particles non-minimally coupled to the gravitational background where higher order curvature invariants are present. The coupling gives rise to an additional force inducing a non-geodesics motion of particles. This fact allows a strong emission of radiation by gravitationally accelerated particles. As we will show with some specific model, the energy emission is of the same order of magnitude of that characterizing the Gamma Ray Burst physics. Alternatively, strong curvature regimes can be considered as a natural mechanism for the generation of highly energetic astrophysical events.
The emission of Gamma Ray Bursts as a test-bed for modified gravity
Salvatore Capozziello; Gaetano Lambiase
2015-09-19T23:59:59.000Z
The extreme physical conditions of Gamma Ray Bursts can constitute a useful observational laboratory to test theories of gravity where very high curvature regimes are involved. Here we propose a sort of curvature engine capable, in principle, of explaining the huge energy emission of Gamma Ray Bursts. Specifically, we investigate the emission of radiation by charged particles non-minimally coupled to the gravitational background where higher order curvature invariants are present. The coupling gives rise to an additional force inducing a non-geodesics motion of particles. This fact allows a strong emission of radiation by gravitationally accelerated particles. As we will show with some specific model, the energy emission is of the same order of magnitude of that characterizing the Gamma Ray Burst physics. Alternatively, strong curvature regimes can be considered as a natural mechanism for the generation of highly energetic astrophysical events. Possible applications to cosmology are discussed.
Hendi, Seyed Hossein; Panah, Behzad Eslam
2015-01-01T23:59:59.000Z
In this paper, we are considering two first order corrections to both gravity and gauge sides of the Einstein-Maxwell gravity: Gauss-Bonnet gravity and quadratic Maxwell invariant as corrections. We obtain horizonless magnetic solutions by implying a metric which representing a topological defect. We analyze the geometric properties of the solutions and investigate the effects of both corrections, and find that these solutions may be interpreted as the magnetic branes. We study the singularity condition and find a nonsingular spacetime with a conical geometry. We also investigate the effects of different parameters on deficit angle of spacetime near the origin.
Light deflection in Weyl gravity: critical distances for photon paths
S. Pireaux
2004-03-16T23:59:59.000Z
The Weyl gravity appears to be a very peculiar theory. The contribution of the Weyl linear parameter to the effective geodesic potential is opposite for massive and nonmassive geodesics. However, photon geodesics do not depend on the unknown conformal factor, unlike massive geodesics. Hence light deflection offers an interesting test of the Weyl theory. In order to investigate light deflection in the setting of Weyl gravity, we first distinguish between a weak field and a strong field approximation. Indeed, the Weyl gravity does not turn off asymptotically and becomes even stronger at larger distances. We then take full advantage of the conformal invariance of the photon effective potential to provide the key radial distances in Weyl gravity. According to those, we analyze the weak and strong field regime for light deflection. We further show some amazing features of the Weyl theory in the strong regime.
Ground Gravity Survey At Neal Hot Springs Geothermal Area (U...
Hot Springs. Data from these surveys will be integrated with older data from Chevron Minerals 1979 drill hole. Notes The gravity survey covered an area of approximately 34 km2...
Regional Gravity Survey of the Northern Great Salt Lake Desert...
Northern Great Salt Lake Desert and Adjacent Areas in Utah, Nevada, and Idaho Jump to: navigation, search OpenEI Reference LibraryAdd to library Journal Article: Regional Gravity...
An alternative derivation of the Minimal massive 3D gravity
Ahmet Baykal
2014-12-23T23:59:59.000Z
By using the algebra of exterior forms and the first order formalism with constraints, an alternative derivation of the field equations for the Minimal massive 3D gravity model is presented.
Application Of Gravity And Deep Dipole Geoelectrics In The Volcanic...
Of Mt Etna (Sicily) Jump to: navigation, search OpenEI Reference LibraryAdd to library Journal Article: Application Of Gravity And Deep Dipole Geoelectrics In The Volcanic Area Of...
Ionospheric acoustic and gravity waves associated with midlatitude thunderstorms
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Lay, Erin H.; Shao, Xuan -Min; Kendrick, Alexander K.; Carrano, Charles S.
2015-07-30T23:59:59.000Z
Acoustic waves with periods of 24 min and gravity waves with periods of 616 min have been detected at ionospheric heights (25350 km) using GPS total electron content measurements. The area disturbed by these waves and the wave amplitudes have been associated with underlying thunderstorm activity. A statistical study comparing Next Generation Weather Radar thunderstorm measurements with ionospheric acoustic and gravity waves in the midlatitude U.S. Great Plains region was performed for the time period of MayJuly 2005. An increase of ionospheric acoustic wave disturbed area and amplitude is primarily associated with large thunderstorms (mesoscale convective systems). Ionospheric gravity wavemore ğdisturbed area and amplitude scale with thunderstorm activity, with even small storms (i.e., individual storm cells) producing an increase of gravity waves.Ğ less
Sudarshan Ananth; Mahendra Mali
2015-04-11T23:59:59.000Z
We derive a closed form expression for the light-cone Lagrangian describing pure gravity on a four-dimensional de Sitter background. We provide a perturbative expansion, of this Lagrangian, to cubic order in the fields.
Mixed convection and heat management in the Mars gravity biosatellite
Marsh, Jesse B. (Jesse Benjamin)
2007-01-01T23:59:59.000Z
The Mars Gravity Biosatellite will house fifteen mice in a low Earth orbit satellite spinning about its longitudinal axis. The satellite's payload thermal control system will reject heat through the base of the payload ...
Ground Gravity Survey At Dixie Valley Geothermal Area (Iovenitti...
project area. These data were used in conjunction with past gravity data reported in by Smith et al (2001) and Blackwell et al (2005). The analysis of these data had not been...
The Basics of Water Waves Theory for Analogue Gravity
Germain Rousseaux
2012-03-14T23:59:59.000Z
This chapter gives an introduction to the connection between the physics of water waves and analogue gravity. Only a basic knowledge of fluid mechanics is assumed as a prerequisite.
Entropy and Area of Black Holes in Loop Quantum Gravity
I. B. Khriplovich
2002-03-31T23:59:59.000Z
Simple arguments related to the entropy of black holes strongly constrain the spectrum of the area operator for a Schwarzschild black hole in loop quantum gravity. In particular, this spectrum is fixed completely by the assumption that the black hole entropy is maximum. Within the approach discussed, one arrives in loop quantum gravity at a quantization rule with integer quantum numbers $n$ for the entropy and area of a black hole.
Gravity Control Propulsion: Towards a General Relativistic Approach
O. Bertolami; F. G. Pedro
2006-10-16T23:59:59.000Z
Evaluation of gravity control concepts should be examined with respect to currently known physical theories. In this work we study the hypothetical conversion of gravitational potential energy into kinetic energy using the formalism of general relativity. We show that the energy involved in the process greatly exceeds the Newtonian estimate, given the nature of general relativity. We conclude that the impact of any gravity manipulation for propulsion greatly depends fundamentally on its exact definition.
A Hopf Algebra Structure in Self-dual Gravity
Hugo Garcia-Compean; Laura E. Morales; Jerzy F. Plebanski
1996-01-20T23:59:59.000Z
The two-dimensional non-linear sigma model approach to Self-dual Yang-Mills theory and to Self-dual gravity given by Q-Han Park is an example of the deep interplay between two and four dimensional physics. In particular, Husain's two-dimensional chiral model approach to Self-dual gravity is studied. We show that the infinite hierarchy of conservation laws associated to the Husain model carries implicitly a hidden infinite Hopf algebra structure.
Gravity-free hydraulic jumps and metal femtocups
Rama Govindarajan; Manikandan Mathur; Ratul DasGupta; N. R. Selvi; Neena Susan John; G. U. Kulkarni
2006-10-03T23:59:59.000Z
Hydraulic jumps created by gravity are seen every day in the kitchen sink. We show that at small scales a circular hydraulic jump can be created in the absence of gravity, by surface tension. The theory is motivated by our experimental finding of a height discontinuity in spreading submicron molten metal droplets created by pulsed-laser ablation. By careful control of initial conditions, we show that this leads to solid femtolitre cups of gold, silver, copper, niobium and tin.
J. W. Maluf
2003-04-01T23:59:59.000Z
We show that the coupling of a Dirac spinor field with the gravitational field in the teleparallel equivalent of general relativity is consistent. For an arbitrary SO(3,1) connection there are two possibilities for the coupling of the spinor field with the gravitational field. The problems of consistency raised by Y. N. Obukhov and J. G. Pereira in the paper {\\it Metric-affine approach to teleparallel gravity} [gr-qc/0212080] take place only in the framework of one particular coupling. By adopting an alternative coupling the consistency problem disappears.
Specification No. 203-HJT-9004 R1 Specification for the
McDonald, Kirk
.S. DEPARTMENT OF ENERGY April 10, 2006 #12;Specification for Titanium Components MERIT High Power Mercury Titanium Components August 14, 2006 #12;Specification for Titanium Components MERIT High Power Mercury MODULE TITANIUM COMPONENTS Prepared by: V.B. Graves (Oak Ridge National Laboratory) P. T. Spampinato (Oak
Gravity stabilized thermal miscible displacement process
Vogel, J.V.
1987-10-06T23:59:59.000Z
A method is described of recovering viscous hydrocarbons from a subterranean reservoir. The reservoir is penetrated by at least one injection well and one production well. The injection well is in fluid communication with the upper portion of the reservoir and the production well is in fluid communication with the lower portion of the reservoir. The injection well and the production well defines a fluid flow path therebetween. The method comprises the steps of: (a) injecting a steam-solvent vapor mixture into the upper portion of the reservoir through the injection well. The steam-solvent vapor mixture is undersaturated in solvent and saturated with steam; (b) reducing the viscosity of the hydrocarbons by heat released upon condensation of the steam-solvent vapor mixture and reducing the viscosity of the hydrocarbons further upon condensation of solvent vapors. The condensed solvent vapors goes into solution with the hydrocarbons; and (c) collecting a mixture of hydrocarbons and solvent accumulated at the bottom of the production well substantially entirely under the force of gravity.
Quantization of neutron in Earth's gravity
Pulak Ranjan Giri
2007-08-22T23:59:59.000Z
Gravity is the weakest of all four known forces in the universe. Quantum states of an elementary particle due to such a weak field is certainly very shallow and would therefore be an experimental challenge to detect. Recently an experimental attempt was made by V. V. Nesvizhevsky et al., Nature 415, 297 (2002), to measure the quantum states of a neutron, which shows that ground state and few excited states are \\sim 10^{-12}eV. We show that the energy of the ground state of a neutron confined above Earth's surface should be \\sim 10^{-37}eV. The experimentally observed energy levels are 10^{25} times deeper than the actual energy levels it should be and thus certainly not due to gravitational effect of Earth. Therefore the correct interpretation for the painstaking experimental results of Ref. \\cite{nes1} is due to the confinement potential of a one dimensional box of length L \\sim 50\\mu m, generated from the experimental setup as commented before \\cite{hansoon}. Our results thus creates a new challenge to the experimentalist to resolve the shallow energy levels of the neutron in Earth's gravitational field in future.
Scalar-tensor gravity and conformal continuations
Kirill A. Bronnikov
2002-03-30T23:59:59.000Z
Global properties of vacuum static, spherically symmetric configurations are studied in a general class of scalar-tensor theories (STT) of gravity in various dimensions. The conformal mapping between the Jordan and Einstein frames is used as a tool. Necessary and sufficient conditions are found for the existence of solutions admitting a conformal continuation (CC). The latter means that a singularity in the Einstein-frame manifold maps to a regular surface S_(trans) in the Jordan frame, and the solution is then continued beyond this surface. S_(trans) can be an ordinary regular sphere or a horizon. In the second case, S_(trans) proves to connect two epochs of a Kantowski-Sachs type cosmology. It is shown that, in an arbitrary STT, with arbitrary potential functions $U(\\phi)$, the list of possible types of causal structures of vacuum space-times is the same as in general relativity with a cosmological constant. This is true even for conformally continued solutions. It is found that when S_(trans) is an ordinary sphere, one of the generic structures appearing as a result of CC is a traversable wormhole. Two explicit examples are presented: a known solution illustrating the emergence of singularities and wormholes, and a nonsingular 3-dimensional model with an infinite sequence of CCs.
Scale-invariant gravity: Spacetime recovered
Bryan Kelleher
2004-07-28T23:59:59.000Z
The configuration space of general relativity is superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms. However, it has been argued that the configuration space for gravity should be conformal superspace - the space of all Riemannian 3-metrics modulo diffeomorphisms and conformal transformations. Recently a manifestly 3-dimensional theory was constructed with conformal superspace as the configuration space. Here a fully 4-dimensional action is constructed so as to be invariant under conformal transformations of the 4-metric using general relativity as a guide. This action is then decomposed to a (3+1)-dimensional form and from this to its Jacobi form. The surprising thing is that the new theory turns out to be precisely the original 3-dimensional theory. The physical data is identified and used to find the physical representation of the theory. In this representation the theory is extremely similar to general relativity. The clarity of the 4-dimensional picture should prove very useful for comparing the theory with those aspects of general relativity which are usually treated in the 4-dimensional framework.
Testing Gravity with Cold-Atom Interferometers
G. W. Biedermann; X. Wu; L. Deslauriers; S. Roy; C. Mahadeswaraswamy; M. A. Kasevich
2014-12-10T23:59:59.000Z
We present a horizontal gravity gradiometer atom interferometer for precision gravitational tests. The horizontal configuration is superior for maximizing the inertial signal in the atom interferometer from a nearby proof mass. In our device, we have suppressed spurious noise associated with the horizonal configuration to achieve a differential acceleration sensitivity of 4.2$\\times10^{-9}g/\\sqrt{Hz}$ over a 70 cm baseline or 3.0$\\times10^{-9}g/\\sqrt{Hz}$ inferred per accelerometer. Using the performance of this instrument, we characterize the results of possible future gravitational tests. We complete a proof-of-concept measurement of the gravitational constant with a precision of 3$\\times10^{-4}$ that is competitive with the present limit of 1.2$\\times10^{-4}$ using other techniques. From this measurement, we provide a statistical constraint on a Yukawa-type fifth force at 8$\\times$10$^{-3}$ near the poorly known length scale of 10 cm. Limits approaching 10$^{-5}$ appear feasible. We discuss improvements that can enable uncertainties falling well below 10$^{-5}$ for both experiments.
Non-Singular Cosmology in Modified Gravity
J. W. Moffat
2007-10-24T23:59:59.000Z
A non-singular cosmology is derived in modified gravity (MOG) with a varying gravitational coupling strength $G(t)=G_N\\xi(t)$. Assuming that the curvature $k$, the cosmological constant $\\Lambda$ and $\\rho$ vanish at $t=0$, we obtain a non-singular universe with a negative pressure, $p_G < 0$. Quantum fluctuations at $t\\sim 0$ produce creation of pairs of particles from the vacuum explaining the origin of matter. The universe expands for $t\\to \\infty$ according to the standard radiation and matter dominated solutions. The arrow of time reverses at $t=0$ always pointing in the direction of increasing entropy ${\\cal S}$ and the entropy is at a minimum value at $t=0$, solving the conundrum of the Second Law of Thermodynamics. The Hubble radius $H^{-1}(t)$ is infinite at $t=0$ removing the curvature and particle horizons. The negative pressure $p_G$ generated by the scalar field $\\xi$ at $t\\sim 0$ can produce quantum spontaneous creation of particles explaining the origin of matter and radiation.
Evaluation of an enhanced gravity-based fine-coal circuit for high-sulfur coal
Mohanty, M.K.; Samal, A.R.; Palit, A. [South Illinois University, Carbondale, IL (United States). Dept. of Mining & Mineral Resources Engineering
2008-02-15T23:59:59.000Z
One of the main objectives of this study was to evaluate a fine-coal cleaning circuit using an enhanced gravity separator specifically for a high sulfur coal application. The evaluation not only included testing of individual unit operations used for fine-coal classification, cleaning and dewatering, but also included testing of the complete circuit simultaneously. At a scale of nearly 2 t/h, two alternative circuits were evaluated to clean a minus 0.6-mm coal stream utilizing a 150-mm-diameter classifying cyclone, a linear screen having a projected surface area of 0.5 m{sup 2}, an enhanced gravity separator having a bowl diameter of 250 mm and a screen-bowl centrifuge having a bowl diameter of 500 mm. The cleaning and dewatering components of both circuits were the same; however, one circuit used a classifying cyclone whereas the other used a linear screen as the classification device. An industrial size coal spiral was used to clean the 2- x 0.6-mm coal size fraction for each circuit to estimate the performance of a complete fine-coal circuit cleaning a minus 2-mm particle size coal stream. The 'linear screen + enhanced gravity separator + screen-bowl circuit' provided superior sulfur and ash-cleaning performance to the alternative circuit that used a classifying cyclone in place of the linear screen. Based on these test data, it was estimated that the use of the recommended circuit to treat 50 t/h of minus 2-mm size coal having feed ash and sulfur contents of 33.9% and 3.28%, respectively, may produce nearly 28.3 t/h of clean coal with product ash and sulfur contents of 9.15% and 1.61 %, respectively.
Gas Slow Control System Specifications
Roma "La Sapienza", Università di
AMS-02 TRD Gas Slow Control System Specifications v 4.2 26-06-2006 A. Bartoloni, B. Borgia, F FUNCTIONAL DESCRIPTION 5 3. GAS CONTROL SYSTEM 8 4. CONTROL SYSTEM COMPONENTS 12 a. Universal Control System. Specifications 38 5. CONTROL SYSTEM TESTING AND VERIFICATION 41 6. CONTROL SYSTEM OPERATIONS 41 a. Ground
Hanford Site environmental management specification
Grygiel, M.L.
1998-06-10T23:59:59.000Z
The US Department of Energy, Richland Operations Office (RL) uses this Hanford Site Environmental Management Specification (Specification) to document top-level mission requirements and planning assumptions for the prime contractors involved in Hanford Site cleanup and infrastructure activities under the responsibility of the US Department of Energy, Office of Environmental Management. This Specification describes at a top level the activities, facilities, and infrastructure necessary to accomplish the cleanup of the Hanford Site and assigns this scope to Site contractors and their respective projects. This Specification also references the key National Environmental Policy Act of 1969 (NEPA), Comprehensive Environmental Response, Compensation, and Liability Act of 1980 (CERCLA), and safety documentation necessary to accurately describe the cleanup at a summary level. The information contained in this document reflects RL`s application of values, priorities, and critical success factors expressed by those involved with and affected by the Hanford Site project. The prime contractors and their projects develop complete baselines and work plans to implement this Specification. These lower-level documents and the data that support them, together with this Specification, represent the full set of requirements applicable to the contractors and their projects. Figure 1-1 shows the relationship of this Specification to the other basic Site documents. Similarly, the documents, orders, and laws referenced in this specification represent only the most salient sources of requirements. Current and contractual reference data contain a complete set of source documents.
A cyclic cosmological model based on the f(?) modified theory of gravity
Yaoming Shi
2011-07-02T23:59:59.000Z
We consider FLRW cosmological models for perfect fluid (with rho as the energy density) in the frame work of the f(rho) modified theory of gravity [V. N. Tunyak, Russ. Phys. J. 21, 1221 (1978); J. R. Ray, L. L. Smalley, Phys. Rev. D. 26, 2615 (1982) ]. This theory, with total Lagrangian R-f(rho), can be considered as a cousin of the F(R) theory of gravity with total Lagrangian F(R)-rho. We can pick proper function forms f(rho) to achieve, as the F(R) theory does, the following 4 specific goals, (1) producing a non-singular cosmological model (Ricci scalar and Ricci tensor curvature are bounded); (2) explaining the cosmic early inflation and late acceleration in a unified fashion; (3) passing the solar system tests; (4) unifying the dark matter with dark energy. In addition we also achieve goal number (5): unify the regular matter/energy with dark matter/energy in a seamless fashion. The mathematics is simplified because in the f(rho) theory the leading terms in Einstein's equations are linear in second order derivative of metric wrt coordinates but in the F(R) theory the leading terms are linear in fourth order derivative of metric wrt coordinates.
Matter Bounce Loop Quantum Cosmology from $F(R)$ Gravity
S. D. Odintsov; V. K. Oikonomou
2014-12-04T23:59:59.000Z
Using the reconstruction method, we investigate which $F(R)$ theories, with or without the presence of matter fluids, can produce the matter bounce scenario of holonomy corrected Loop Quantum Cosmology. We focus our study in two limits of the cosmic time, the large cosmic time limit and the small cosmic time limit. For the former, we found that, in the presence of non-interacting and non-relativistic matter, the $F(R)$ gravity that reproduces the late time limit of the matter bounce solution is actually the Einstein-Hilbert gravity plus a power law term. In the early time limit, since it corresponds to large spacetime curvatures, assuming that the Jordan frame is described by a general metric that when it is conformally transformed to the Einstein frame, produces an accelerating Friedmann-Robertson-Walker metric, we found explicitly the scalar field dependence on time. After demonstrating that the solution in the Einstein frame is indeed accelerating, we calculate the spectral index derived from the Einstein frame scalar-tensor counterpart theory of the $F(R)$ theory and compare it with the Planck experiment data. In order to implement the resulting picture, we embed the $F(R)$ gravity explicitly in a Loop Quantum Cosmology framework by introducing holonomy corrections to the $F(R)$ gravity. In this way, the resulting inflation picture corresponding to the $F(R)$ gravity can be corrected in order it coincides to some extent with the current experimental data.
Unscreening modified gravity in the matter power spectrum
Lombriser, Lucas; Mead, Alexander
2015-01-01T23:59:59.000Z
Viable modifications of gravity that may produce cosmic acceleration need to be screened in high-density regions such as the Solar System, where general relativity is well tested. Screening mechanisms also prevent strong anomalies in the large-scale structure and limit the constraints that can be inferred on these gravity models from cosmology. We find that by suppressing the contribution of the screened high-density regions in the matter power spectrum, allowing a greater contribution of unscreened low densities, modified gravity models can be more readily discriminated from the concordance cosmology. Moreover, by variation of density thresholds, degeneracies with other effects may be dealt with more adequately. Specializing to chameleon gravity as a worked example for screening in modified gravity, employing N-body simulations of f(R) models and the halo model of chameleon theories, we demonstrate the effectiveness of this method. We find that a percent-level measurement of the clipped power at k < 0.3 h...
Horava-Lifshitz Gravity From Dynamical Newton-Cartan Geometry
Jelle Hartong; Niels A. Obers
2015-04-28T23:59:59.000Z
Recently it has been established that torsional Newton-Cartan (TNC) geometry is the appropriate geometrical framework to which non-relativistic field theories couple. We show that when these geometries are made dynamical they give rise to Horava-Lifshitz (HL) gravity. Projectable HL gravity corresponds to dynamical Newton-Cartan (NC) geometry without torsion and non-projectable HL gravity corresponds to dynamical NC geometry with twistless torsion (hypersurface orthogonal foliation). We build a precise dictionary relating all fields (including the scalar khronon), their transformations and other properties in both HL gravity and dynamical TNC geometry. We use TNC invariance to construct the effective action for dynamical twistless torsional Newton-Cartan geometries in 2+1 dimensions for dynamical exponent 1Thompson as coming from the Bargmann extension of the local Galilean algebra that acts on the tangent space to TNC geometries. We argue that TNC geometry, which is manifestly diffeomorphism covariant, is a natural geometrical framework underlying HL gravity and discuss some of its implications.
Unscreening modified gravity in the matter power spectrum
Lucas Lombriser; Fergus Simpson; Alexander Mead
2015-01-20T23:59:59.000Z
Viable modifications of gravity that may produce cosmic acceleration need to be screened in high-density regions such as the Solar System, where general relativity is well tested. Screening mechanisms also prevent strong anomalies in the large-scale structure and limit the constraints that can be inferred on these gravity models from cosmology. We find that by suppressing the contribution of the screened high-density regions in the matter power spectrum, allowing a greater contribution of unscreened low densities, modified gravity models can be more readily discriminated from the concordance cosmology. Moreover, by variation of density thresholds, degeneracies with other effects may be dealt with more adequately. Specializing to chameleon gravity as a worked example for screening in modified gravity, employing N-body simulations of f(R) models and the halo model of chameleon theories, we demonstrate the effectiveness of this method. We find that a percent-level measurement of the clipped power at k Solar System tests or distance indicators in unscreened dwarf galaxies.
First tsunami gravity wave detection in ionospheric radio occultation data
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Coïsson, Pierdavide; Lognonné, Philippe; Walwer, Damian; Rolland, Lucie M.
2015-05-09T23:59:59.000Z
After the 11 March 2011 earthquake and tsunami off the coast of Tohoku, the ionospheric signature of the displacements induced in the overlying atmosphere has been observed by ground stations in various regions of the Pacific Ocean. We analyze here the data of radio occultation satellites, detecting the tsunami-driven gravity wave for the first time using a fully space-based ionospheric observation system. One satellite of the Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) recorded an occultation in the region above the tsunami 2.5 h after the earthquake. The ionosphere was sounded from top to bottom, thus providing themore ğvertical structure of the gravity wave excited by the tsunami propagation, observed as oscillations of the ionospheric Total Electron Content (TEC). The observed vertical wavelength was about 50 km, with maximum amplitude exceeding 1 total electron content unit when the occultation reached 200 km height. We compared the observations with synthetic data obtained by summation of the tsunami-coupled gravity normal modes of the Earth/Ocean/atmosphere system, which models the associated motion of the ionosphere plasma. These results provide experimental constraints on the attenuation of the gravity wave with altitude due to atmosphere viscosity, improving the understanding of the propagation of tsunami-driven gravity waves in the upper atmosphere. They demonstrate that the amplitude of the tsunami can be estimated to within 20% by the recorded ionospheric data.Ğ less
Cell Data Sheet Specification (Presentation)
Kurtz, S.
2012-03-01T23:59:59.000Z
The presentation shows a brief status report on the development of a specification being considered by IEC TC82 WG7 for a concentrator cell data sheet and solicits suggestions from the community.
Backreaction effects due to matter coupled higher derivative gravity
Lata Kh Joshi; P. Ramadevi
2014-11-28T23:59:59.000Z
AdS-hydrodynamics has proven to be a useful tool for obtaining transport coefficients observed in the collective flow of strongly coupled fluids like quark gluon plasma (QGP). Particularly, the ratio of shear viscosity to entropy density ${\\eta/ s}$ obtained from elliptic flow measurements can be matched with the computation done in the dual gravity theory. The experimentally observed temperature dependence of ${\\eta/ s}$ requires the study of scalar matter coupled AdS gravity including higher derivative curvature corrections. We obtain the backreaction to the metric for such a matter coupled AdS gravity in $D$-dimensional spacetime due to the higher derivative curvature corrections. Then, we present the backreaction corrections to shear-viscosity $\\eta$ and entropy density $s$.
Exotic Statistics for Ordinary Particles in Quantum Gravity
John Swain
2008-05-15T23:59:59.000Z
Objects exhibiting statistics other than the familiar Bose and Fermi ones are natural in theories with topologically nontrivial objects including geons, strings, and black holes. It is argued here from several viewpoints that the statistics of ordinary particles with which we are already familiar are likely to be modified due to quantum gravity effects. In particular, such modifications are argued to be present in loop quantum gravity and in any theory which represents spacetime in a fundamentally piecewise-linear fashion. The appearance of unusual statistics may be a generic feature (such as the deformed position-momentum uncertainty relations and the appearance of a fundamental length scale) which are to be expected in any theory of quantum gravity, and which could be testable.
Analogy between turbulence and quantum gravity: beyond Kolmogorov's 1941 theory
S. Succi
2011-11-14T23:59:59.000Z
Simple arguments based on the general properties of quantum fluctuations have been recently shown to imply that quantum fluctuations of spacetime obey the same scaling laws of the velocity fluctuations in a homogeneous incompressible turbulent flow, as described by Kolmogorov 1941 (K41) scaling theory. Less noted, however, is the fact that this analogy rules out the possibility of a fractal quantum spacetime, in contradiction with growing evidence in quantum gravity research. In this Note, we show that the notion of a fractal quantum spacetime can be restored by extending the analogy between turbulence and quantum gravity beyond the realm of K41 theory. In particular, it is shown that compatibility of a fractal quantum-space time with the recent Horava-Lifshitz scenario for quantum gravity, implies singular quantum wavefunctions. Finally, we propose an operational procedure, based on Extended Self-Similarity techniques, to inspect the (multi)-scaling properties of quantum gravitational fluctuations.
Nonlocal resonances in weak turbulence of gravity-capillary waves
Quentin Aubourg; Nicolas Mordant
2015-03-13T23:59:59.000Z
We report a laboratory investigation of weak turbulence of water surface waves in the gravity-capillary crossover. By using time-space resolved profilometry and a bicoherence analysis, we observe that the nonlinear processes involve 3-wave resonant interactions. By studying the solutions of the resonance conditions we show that the nonlinear interaction is dominantly 1D and involves collinear wave vectors. Furthermore taking into account the spectral widening due to weak nonlinearity explains that nonlocal interactions are possible between a gravity wave and high frequency capillary ones. We observe also that nonlinear 3-wave coupling is possible among gravity waves and we raise the question of the relevance of this mechanism for oceanic waves.
Constraints on the quantum gravity scale from kappa - Minkowski spacetime
A. Borowiec; Kumar S. Gupta; S. Meljanac; A. Pachol
2010-11-18T23:59:59.000Z
We compare two versions of deformed dispersion relations (energy vs momenta and momenta vs energy) and the corresponding time delay up to the second order accuracy in the quantum gravity scale (deformation parameter). A general framework describing modified dispersion relations and time delay with respect to different noncommutative kappa -Minkowski spacetime realizations is firstly proposed here and it covers all the cases introduced in the literature. It is shown that some of the realizations provide certain bounds on quadratic corrections, i.e. on quantum gravity scale, but it is not excluded in our framework that quantum gravity scale is the Planck scale. We also show how the coefficients in the dispersion relations can be obtained through a multiparameter fit of the gamma ray burst (GRB) data.
Extended Theories of Gravity with Generalized Energy Conditions
José P. Mimoso; Francisco S. N. Lobo; Salvatore Capozziello
2014-12-20T23:59:59.000Z
We address the problem of the energy conditions in modified gravity taking into account the additional degrees of freedom related to scalar fields and curvature invariants. The latter are usually interpreted as generalized {\\it geometrical fluids} that differ in meaning with respect to the matter fluids generally considered as sources of the field equations. In extended gravity theories the curvature terms are encapsulated in a tensor $H^{ab}$ and a coupling $g(\\Psi^i)$ that can be recast as effective Einstein field equations, with corrections to the energy-momentum tensor of matter. The formal validity of standard energy inequalities does not assure basic requirements such as the attractive nature of gravity, so we argue that the energy conditions have to be considered in a wider sense.
Direct Detection of Gravity Waves from Neutron Stars
Redouane Al Fakir; William G. Unruh
2008-05-24T23:59:59.000Z
In light of the discovery of the first-ever double pulsar system, PSR J0737-3039, we re-examine an earlier proposal to directly detect gravity waves from neutron stars, which was predicated on a hypothetical system almost identical to the later discovered double pulsar. We re-derive the effect in more detail, and confirm the initial estimate--sometimes doubted in the literature--that it includes a 1/b dependence, where b is the impact parameter of a pulsar with respect to its foreground, gravity-wave emitting, neutron star companion. A coherent modulation in pulsar time-of-arrival measurements of 10 nano-sec/sec is possible. A one-year intermittent experiment on an instrument comparable to the SKA could thus detect the exceedingly faint gravity waves from individual neutron stars.
Asymptotic safety of gravity and the Higgs boson mass
Mikhail Shaposhnikov; Christof Wetterich
2010-01-12T23:59:59.000Z
There are indications that gravity is asymptotically safe. The Standard Model (SM) plus gravity could be valid up to arbitrarily high energies. Supposing that this is indeed the case and assuming that there are no intermediate energy scales between the Fermi and Planck scales we address the question of whether the mass of the Higgs boson $m_H$ can be predicted. For a positive gravity induced anomalous dimension $A_\\lambda>0$ the running of the quartic scalar self interaction $\\lambda$ at scales beyond the Planck mass is determined by a fixed point at zero. This results in $m_H=m_{\\rm min}=126$ GeV, with only a few GeV uncertainty. This prediction is independent of the details of the short distance running and holds for a wide class of extensions of the SM as well. For $A_\\lambda 0$ is favored by explicit computations existing in the literature.
Superbounce and Loop Quantum Cosmology Ekpyrosis from Modified Gravity
V. K. Oikonomou
2015-04-07T23:59:59.000Z
As is known, in modified cosmological theories of gravity many of the cosmologies which could not be generated by standard Einstein gravity, can be consistently described by $F(R)$ theories. Using known reconstruction techniques, we investigate which $F(R)$ theories can lead to a Hubble parameter describing two types of cosmological bounces, the superbounce model, related to supergravity and non-supersymmetric models of contracting ekpyrosis and also the Loop Quantum Cosmology modified ekpyrotic model. Since our method is an approximate method, we investigate the problem at large and small curvatures. As we evince, both models yield power law reconstructed $F(R)$ gravities, with the most interesting new feature being that both lead to accelerating cosmologies, in the large curvature approximation. The mathematical properties of the some Friedmann-Robertson-Walker spacetimes $M$, that describe superbounce-like cosmologies are also pointed out, with regards to the group of curvature collineations $CC(M)$.
Building Energy Data Exchange Specification Scoping Report |...
Office of Energy Efficiency and Renewable Energy (EERE) Indexed Site
Energy Data Exchange Specification Scoping Report Building Energy Data Exchange Specification Scoping Report The Building Energy Data Exchange Specification (BEDES), developed by...
On power-counting renormalizability of Ho?ava gravity with detailed balance
Daniele Vernieri
2015-02-23T23:59:59.000Z
We consider the version of Ho\\v{r}ava gravity where "detailed balance" is consistently implemented, such as to limitate the huge proliferation of couplings in the full theory and to obtain an healthy dynamics at low-energy. Since a superpotential which is third-order in spatial derivatives is not sufficient to guarantee the power-counting renormalizability of the spin-0 graviton, then one needs to go an order beyond in derivatives, building up a superpotential up to fourth-order spatial derivatives. Here, we perturb the action to quadratic order around flat space, and show that power-counting renormalizability of the spin-0 graviton is achieved only by setting to zero a specific coupling of the theory, while the spin-2 graviton is always power-counting renormalizable for any choice of the couplings. This result raises serious doubts about the use of detailed balance.
On power-counting renormalizability of Ho\\v{r}ava gravity with detailed balance
Vernieri, Daniele
2015-01-01T23:59:59.000Z
We consider the version of Ho\\v{r}ava gravity where "detailed balance" is consistently implemented, such as to limitate the huge proliferation of couplings in the full theory and to obtain an healthy dynamics at low-energy. Since a superpotential which is third-order in spatial derivatives is not sufficient to guarantee the power-counting renormalizability of the spin-0 graviton, then one needs to go an order beyond in derivatives, building up a superpotential up to fourth-order spatial derivatives. Here, we perturb the action to quadratic order around flat space, and show that power-counting renormalizability of the spin-0 graviton is achieved only by setting to zero a specific coupling of the theory, while the spin-2 graviton is always power-counting renormalizable for any choice of the couplings. This result raises serious doubts about the use of detailed balance.
Flat Spacetime Cosmology in a Scalar-Tensor Theory of Gravity
Meir Shimon
2015-03-24T23:59:59.000Z
A scalar-tensor theory of gravity, linear in the scalar curvature, is formulated in which $G$, particle masses, and a cosmological constant are allowed to vary. The theory yields a flat and static cosmological model with time-independent angular scales. No flatness and horizon `problems' arise in this model; consequently, there is no need for an inflationary expansion phase. Lack of (global) evolutionary timescales implies that there are no cosmological coincidences, including the near equality of the energy densities of dark energy and dark matter. Irrespective of the specifics of the model, it can be shown that the energy densities of dark energy ($\\rho_{DE}$), dark matter ($\\rho_{DM}$), and (non-relativistic) baryons ($\\rho_{b}$), are related by $\\rho_{DE}=2\\rho_{DM}+\\rho_{b}/2$, in good agreement with current observations, if DE and DM are associated with the kinetic and potential energy densities of the scalar fields.
Static self-gravitating many-body systems in Einstein gravity
Lars Andersson; Berndt G. Schmidt
2009-05-08T23:59:59.000Z
We consider the problem of constructing static, elastic, many-body systems in Einstein gravity. The solutions constructed are deformations of static many-body configurations in Newtonian gravity. No symmetry assumptions are made.
The impact of gravity segregation on multiphase non-Darcy flow in hydraulically fractured gas wells
Dickins, Mark Ian
2008-10-10T23:59:59.000Z
and saturations in the fracture agrees well with reservoir simulation. Gravity segregation occurs in moderate-to-high conductivity fractures. Gravity segregation impacts effective fracture conductivity when gas and liquid are being produced at all water-gas ratios...
A Modified Gravity and its Consequences for the Solar System, Astrophysics and Cosmology
J. W. Moffat
2006-12-17T23:59:59.000Z
A relativistic modified gravity (MOG) theory leads to a self-consistent, stable gravity theory that can describe the solar system, galaxy and clusters of galaxies data and cosmology.
Negative mode problem in false vacuum decay with gravity
George Lavrelashvili
2000-04-08T23:59:59.000Z
There is a single negative mode in the spectrum of small perturbations about the tunneling solutions describing a metastable vacuum decay in flat spacetime. This mode is needed for consistent description of decay processes. When gravity is included the situation is more complicated. An approach based on elimination of scalar field perturbations shows no negative mode, whereas the recent approach based on elimination of gravitational perturbations indicates presence of a negative mode. In this contribution we analyse and compare the present approaches to the negative mode problem in false vacuum decay with gravity.
Consistent Evolution with Different Time-Slicings in Quantum Gravity
R. Cosgrove
1996-02-20T23:59:59.000Z
Rovelli's `` quantum mechanics without time'' motivates an intrinsically time-slicing independent picture of reduced phase space quantum gravity, which may be described as ``quantization after evolution''. Sufficient criteria for carrying out quantization after evolution are developed in terms of a general concept of the classical limit of quantum mechanics. If these criteria are satisfied then it is possible to have consistent unitary evolution of operators, with respect to an infinite parameter family of time-slicings (and probably all time-slicings), with the correct classical limit. The criteria are particularly amenable to study in (2+1)-dimensional gravity, where the reduced phase space is finite dimensional.
Dynamics of the Cosmological Apparent Horizon: Surface Gravity & Temperature
Alexis Helou
2015-02-14T23:59:59.000Z
In the context of thermodynamics applied to our cosmological apparent horizon, we explicit in greater details our previous work which established the Friedmann Equations from projection of Hayward's Unified First Law. In particular, we show that the dynamical Hayward-Kodama surface gravity is perfectly well-defined and is suitable for this derivation. We then relate this surface gravity to a physical notion of temperature, and show this has constant, positive sign for any kind of past-inner trapping horizons. Hopefully this will clarify the choice of temperature in a dynamical Friedmann-Lema\\^itre-Roberston-Walker spacetime.
Irrotational-fluid cosmologies in fourth-order gravity
Amare Abebe; Maye Elmardi
2015-04-25T23:59:59.000Z
In this paper, we explore classes of irrotational-fluid cosmological models in the context of f(R)-gravity in an attempt to put some theoretical and mathematical restrictions on the form of the f(R) gravitational Lagrangian. In particular, we investigate the consistency of linearised dust models for shear-free cases as well as in the limiting cases when either the gravito-magnetic or gravito-elecric components of the Weyl tensor vanish. We also discuss the existence and consistency of classes of non-expanding irrotational spacetimes in f(R)-gravity.
Evidence for cenozoic rifting in Thailand from gravity modeling
Ohnstad, Tiffany A.
1990-01-01T23:59:59.000Z
at the teriiunation of a large NiVW-SSE trending strike-slip fault related to the extrusion of a. portion of Indochina away froni India, as it collided with Eurasia. . Rifting did not continue alotlg the trencl of the strike-slip fault zone; instead... gravity anomalies from the gndderl geoid heights, a two-diuieusional forur of Lap)&ace's equation in cartesian coordinates was?sed: d~g, , 'i3s =- g?(r3, , 'i)z(?~, 'oz) ? 8/c)y(clh/ dy)) wher'e 2 7 is the gravit'y anoulalv to bc dp'terminpcl, Ji? ls...
On the critical temperatures of superconductors: a quantum gravity approach
Andrea Gregori
2010-07-06T23:59:59.000Z
We consider superconductivity in the light of the quantum gravity theoretical framework introduced in [1]. In this framework, the degree of quantum delocalization depends on the geometry of the energy distribution along space. This results in a dependence of the critical temperature characterizing the transition to the superconducting phase on the complexity of the structure of a superconductor. We consider concrete examples, ranging from low to high temperature superconductors, and discuss how the critical temperature can be predicted once the quantum gravity effects are taken into account.
Time machines and traversable wormholes in modified theories of gravity
Francisco S. N. Lobo
2012-12-05T23:59:59.000Z
We review recent work on wormhole geometries in the context of modified theories of gravity, in particular, in f(R) gravity and with a nonminimal curvature-matter coupling, and in the recently proposed hybrid metric-Palatini theory. In principle, the normal matter threading the throat can be shown to satisfy the energy conditions and it is the higher order curvatures terms that sustain these wormhole geometries. We also briefly review the conversion of wormholes into time-machines, explore several of the time travel paradoxes and possible remedies to these intriguing side-effects in wormhole physics.
Gravity Survey of the Carson Sink - Data and Maps
DOE Data Explorer [Office of Scientific and Technical Information (OSTI)]
Faulds, James E.
Preliminary Interpretation of Results: The Carson Sink is a complex composite basin with several major depocenters (Figures 15 and 16). Major depocenters are present in the south?central, east?central, and northeastern parts of the basin. The distribution of gravity anomalies suggests a complex pattern of faulting in the subsurface of the basin, with many fault terminations, step?overs, and accommodation zones. The pattern of faulting implies that other, previously undiscovered blind geothermal systems are likely in the Carson Sink. The gravity survey was completed near the end of this project. Thus, more thorough analysis of the data and potential locations of blind geothermal systems is planned for future work.
Static Charged Black Hole Solutions in Horava-Lifshitz Gravity
Jin-Zhang Tang
2010-01-12T23:59:59.000Z
In the present work, we search static charged black hole solutions to Ho\\v{r}ava-Lifshitz gravity with or without projectability condition. We consider the most general form of action which electromagnetic field couples with Ho\\v{r}ava-Lifshitz gravity. With the projectability condition, we find dS-Reissner-Nordstrom black hole solution in Painlev\\'e-Gullstrand type coordinates in the IR region and a de-Sitter space-time solution in the UV region. Without the projectability condition, in the IR region, we find an especial static charged black hole solution.
SL(2,C) gravity on noncommutative space with Poisson structure
Miao Yangang; Zhang Shaojun [Department of Physics, Nankai University, Tianjin 300071 (China)
2010-10-15T23:59:59.000Z
The Einstein's gravity theory can be formulated as an SL(2,C) gauge theory in terms of spinor notations. In this paper, we consider a noncommutative space with the Poisson structure and construct an SL(2,C) formulation of gravity on such a space. Using the covariant coordinate technique, we build a gauge invariant action in which, according to the Seiberg-Witten map, the physical degrees of freedom are expressed in terms of their commutative counterparts up to the first order in noncommutative parameters.
Minimum length, extra dimensions, modified gravity and black hole remnants
Maziashvili, Michael, E-mail: maziashvili@gmail.com [Particle Physics and Cosmology Group, Ilia State University, 3/5 Cholokashvili Ave., Tbilisi 0162, Georgia (United States)
2013-03-01T23:59:59.000Z
We construct a Hilbert space representation of minimum-length deformed uncertainty relation in presence of extra dimensions. Following this construction, we study corrections to the gravitational potential (back reaction on gravity) with the use of correspondingly modified propagator in presence of two (spatial) extra dimensions. Interestingly enough, for r?0 the gravitational force approaches zero and the horizon for modified Schwarzschild-Tangherlini space-time disappears when the mass approaches quantum-gravity energy scale. This result points out to the existence of zero-temperature black hole remnants in ADD brane-world model.
Power-counting renormalizability of generalized Horava gravity
Visser, Matt
2009-01-01T23:59:59.000Z
In an earlier article [arXiv:0902.0590 [hep-th], Phys. Rev D80 (2009) 025011], I discussed the potential benefits of allowing Lorentz symmetry breaking in quantum field theories. In particular I discussed the perturbative power-counting finiteness of the normal-ordered :P(phi)^{z>=d}_{d+1}: scalar quantum field theories, and sketched the implications for Horava's model of quantum gravity. In the current rather brief addendum, I will tidy up some dangling issues and fill out some of the technical details of the argument indicating the power-counting renormalizability of a z>=d variant of Horava gravity in (d+1) dimensions.
Signatures of fractal clustering of aerosols advected under gravity
Rafael Dias Vilela; Tamás Tél; Alessandro P. S. de Moura; Celso Grebogi
2007-06-15T23:59:59.000Z
Aerosols under chaotic advection often approach a strange attractor. They move chaotically on this fractal set but, in the presence of gravity, they have a net vertical motion downwards. In practical situations, observational data may be available only at a given level, for example at the ground level. We uncover two fractal signatures of chaotic advection of aerosols under the action of gravity. Each one enables the computation of the fractal dimension $D_{0}$ of the strange attractor governing the advection dynamics from data obtained solely at a given level. We illustrate our theoretical findings with a numerical experiment and discuss their possible relevance to meteorology.
Dirac Fields in Loop Quantum Gravity and Big Bang Nucleosynthesis
Martin Bojowald; Rupam Das; Robert J. Scherrer
2008-03-19T23:59:59.000Z
Big Bang nucleosynthesis requires a fine balance between equations of state for photons and relativistic fermions. Several corrections to equation of state parameters arise from classical and quantum physics, which are derived here from a canonical perspective. In particular, loop quantum gravity allows one to compute quantum gravity corrections for Maxwell and Dirac fields. Although the classical actions are very different, quantum corrections to the equation of state are remarkably similar. To lowest order, these corrections take the form of an overall expansion-dependent multiplicative factor in the total density. We use these results, along with the predictions of Big Bang nucleosynthesis, to place bounds on these corrections.
3D gravity with dust: classical and quantum theory
Viqar Husain; Jonathan Ziprick
2015-06-02T23:59:59.000Z
We study the Einstein gravity and dust system in three spacetime dimensions as an example of a non-perturbative quantum gravity model with local degrees of freedom. We derive the Hamiltonian theory in the dust time gauge and show that it has a rich class of exact solutions. These include the Ba\\~nados-Teitelboim-Zanelli black hole, static solutions with naked singularities and travelling wave solutions with dynamical horizons. We give a complete quantization of the wave sector of the theory, including a definition of a self-adjoint spacetime metric operator. This operator is used to demonstrate the quantization of deficit angle and the fluctuation of dynamical horizons.
Ashtekar Formulation of 2+1 Gravity on a Torus
N. Manojlovic; A. Mikovic
1992-04-09T23:59:59.000Z
Pure (2+1)-dimensional Einstein gravity is analysed in the Ashtekar formulation, when the spatial manifold is a torus. We have found a set of globally defined observables, forming a closed algebra. This allowed us to solve the quantum constraints, and to show that the reduced phase space of the Ashtekar formulation is greater then the corresponding space of the Witten formulation. Furthermore, we have found a globally defined time variable which satisfies all the requiriments of an extrinsic time variable in quantum gravity.
Power-counting renormalizability of generalized Horava gravity
Matt Visser
2009-12-24T23:59:59.000Z
In an earlier article [arXiv:0902.0590 [hep-th], Phys. Rev D80 (2009) 025011], I discussed the potential benefits of allowing Lorentz symmetry breaking in quantum field theories. In particular I discussed the perturbative power-counting finiteness of the normal-ordered :P(phi)^{z>=d}_{d+1}: scalar quantum field theories, and sketched the implications for Horava's model of quantum gravity. In the current rather brief addendum, I will tidy up some dangling issues and fill out some of the technical details of the argument indicating the power-counting renormalizability of a z>=d variant of Horava gravity in (d+1) dimensions.
Viscoelastic Suppression of Gravity-Driven Counterflow Instability
Beiersdorfer, P; Layne, D; Magee, E W
2010-01-01T23:59:59.000Z
Attempts to achieve ``top kill'' of actively flowing oil wells by insertion of dense drilling ``muds'', i.e., slurries of dense minerals, from above will fail if the Kelvin-Helmholtz instability in the gravity-driven counterflow produces turbulence that breaks up the denser fluid into small droplets. Here we estimate the droplet size to be sub-mm for fast flows and suggest the addition of a shear-thickening polymer to suppress turbulence. Laboratory experiments show a progression from droplet formation to complete turbulence suppression at the relevant high velocities, illustrating rich new physics accessible by using a shear-thickening liquid in gravity driven counter-streaming flows.
Causality Constraint on Noncritical Einstein-Weyl Gravity
Fu-Wen Shu; Yungui Gong
2014-10-31T23:59:59.000Z
We explore, in the context of AdS/CFT correspondence, the causality constraints on the Noncritical Einstein-Weyl (NEW) gravity model in five dimensions. The scalar and shear channels are considered as small metric perturbations around an AdS black brane background. Our results show that causality analysis on the propagation of these two channels imposes a new bound on the coupling of the Weyl-squared terms in the NEW gravity. This new bound imposes more stringent restrictions than those of the tachyon-free condition, improving predictive power of the theory.
Classical and Quantum Aspects of 1+1 Gravity
T. Kloesch; P. Schaller; T. Strobl
1996-08-02T23:59:59.000Z
We present a classification of all global solutions (with Lorentzian signature) for any general 2D dilaton gravity model. For generic choices of potential-like terms in the Lagrangian one obtains maximally extended solutions on arbitrary non-compact two-manifolds, including various black-hole and kink configurations. We determine all physical quantum states in a Dirac approach. In some cases the spectrum of the (black-hole) mass operator is found to be sensitive to the signature of the theory, which may be relevant in view of current attempts to implement a generalized Wick-rotation in 4D quantum gravity.
Complete Classification of 1+1 Gravity Solutions
T. Kloesch; T. Strobl
1997-11-25T23:59:59.000Z
A classification of the maximally extended solutions for 1+1 gravity models (comprising e.g. generalized dilaton gravity as well as models with non-trivial torsion) is presented. No restrictions are placed on the topology of the arising solutions, and indeed it is found that for generic models solutions on non-compact surfaces of arbitrary genus with an arbitrary non-zero number of holes can be obtained. The moduli space of classical solutions (solutions of the field equations with fixed topology modulo gauge transformations) is parametrized explicitly.
Kolmogorov Algorithmic Complexity and its Probability Interpretation in Quantum Gravity
V. D. Dzhunushaliev
1997-04-16T23:59:59.000Z
The quantum gravity has great difficulties with application of the probability notion. In given article this problem is analyzed according to algorithmic viewpoint. According to A.N. Kolmogorov, the probability notion can be connected with algorithmic complexity of given object. The paper proposes an interpretation of quantum gravity, according to which an appearance of something corresponds to its Kolmogorov's algorithmic complexity. By this viewpoint the following questions are considered: the quantum transition with supplementary coordinates splitting off, the algorithmic complexity of the Schwarzschild black hole is estimated, the redefinition of the Feynman path integral, the quantum birth of the Euclidean Universe with the following changing of the metric signature.
Time Delay Predictions in a Modified Gravity Theory
J. W. Moffat
2006-06-01T23:59:59.000Z
The time delay effect for planets and spacecraft is obtained from a fully relativistic modified gravity theory including a fifth force skew symmetric field by fitting to the Pioneer 10/11 anomalous acceleration data. A possible detection of the predicted time delay corrections to general relativity for the outer planets and future spacecraft missions is considered. The time delay correction to GR predicted by the modified gravity is consistent with the observational limit of the Doppler tracking measurement reported by the Cassini spacecraft on its way to Saturn, and the correction increases to a value that could be measured for a spacecraft approaching Neptune and Pluto.
Thermodynamics on the apparent horizon in generalized gravity theories
Shao-Feng Wu; Bin Wang; Guo-Hong Yang
2008-01-17T23:59:59.000Z
We present a general procedure to construct the first law of thermodynamics on the apparent horizon and illustrate its validity by examining it in some extended gravity theories. Applying this procedure, we can describe the thermodynamics on the apparent horizon in Randall-Sundrum braneworld imbedded in a nontrivial bulk. We discuss the mass-like function which was used to link Friedmann equation to the first law of thermodynamics and obtain its special case which gives the generalized Misner-Sharp mass in Lovelock gravity.
BTZ black hole from (3+1) gravity
M. Cataldo; S. del Campo; A. Garcia
2000-04-07T23:59:59.000Z
We propose an approach for constructing spatial slices of (3+1) spacetimes with cosmological constant but without a matter content, which yields (2+1) vacuum with $\\Lambda$ solutions. The reduction mechanism from (3+1) to (2+1) gravity is supported on a criterion in which the Weyl tensor components are required to vanish together with a dimensional reduction via an appropriate foliation. By using an adequate reduction mechanism from the Pleba\\'nski-Carter[A] solution in (3+1) gravity, the (2+1) BTZ solution can be obtained.
Monte Carlo simulations of 4d simplicial quantum gravity
B. Bruegmann; E. Marinari
1995-04-08T23:59:59.000Z
Dynamical triangulations of four-dimensional Euclidean quantum gravity give rise to an interesting, numerically accessible model of quantum gravity. We give a simple introduction to the model and discuss two particularly important issues. One is that contrary to recent claims there is strong analytical and numerical evidence for the existence of an exponential bound that makes the partition function well-defined. The other is that there may be an ambiguity in the choice of the measure of the discrete model which could even lead to the existence of different universality classes.
Specification No. 203-HJT-9001 R0 Specification for the
McDonald, Kirk
.S. DEPARTMENT OF ENERGY February 5, 2006 #12;Specification for Support Structure MERIT High Power Mercury and provide positional adjustment, and operation of the hydraulic jacks used for height adjustment assembled components shown in the drawing package, o Two (2) hydraulic hand pump/c
Efficient Models for the Evaluation and Estimation of the Gravity Field
Born, George
models. Problem Cubed-Sphere Gravity Model Designed for Fast Evaluation Orbit Propagation/FORMOSAT-3 4 #12;The spherical harmonic gravity model dominates force model execution time 0 10 20 30 40 50 60 Two-Body + Overhead Precession Nutation Gravity (36x36) Lunar-Solar Drag SRP Jacobian (36x36
Localized gravity/topography admittance and correlation spectra on Mars: Implications for
Simons, Mark
Localized gravity/topography admittance and correlation spectra on Mars: Implications for regional] From gravity and topography data collected by the Mars Global Surveyor spacecraft we calculate gravity/topography of an elastic/plastic shell. In regions of high topography on Mars (e.g., the Tharsis rise and associated shield
Gravity-Driven flow of evaporating thin liquid films over substrates with topography
Jimack, Peter
Gravity-Driven flow of evaporating thin liquid films over substrates with topography Gaskell, P. Abstract This paper considers gravity-driven flow of thin liquid films over substrates with topography of gravity-driven flow of thin liquid films over well defined topography, as indicated in Figure 1, in which
Sandwell, David T.
1 Gravity/Topography Transfer Function and Isostatic Geoid Anomalies (Copyright 2002, David T to develop a linear relationship between gravity and topography. This relationship can be used in a variety of ways. (1) If both the topography and gravity are measured over an area that is several times greater
An optimizing reduced order FDS for the tropical Pacific Ocean reduced gravity model
Aluffi, Paolo
An optimizing reduced order FDS for the tropical Pacific Ocean reduced gravity model Zhendong Luoa) for the tropical Pacific Ocean reduced gravity model. Ensembles of data are compiled from transient solutions computed from the discrete equation system derived by FDS for the tropical Pacific Ocean reduced gravity
Impact of boundary conditions on entrainment and transport in gravity currents
Duan, Jinqiao
Impact of boundary conditions on entrainment and transport in gravity currents Vena Pearl Bon on the entrainment and transport of gravity currents. The finding is that gravity currents under these two different difference occurs at medium temperature ranges. Entrainment and transport at high temperatures also show
Evolution of the contact network during tilting cycles of a granular pile under gravity
Staron, Lydie
Evolution of the contact network during tilting cycles of a granular pile under gravity S. Deboeuf of a granular pile undergoing quasi-static tilting cycles in the gravity field. The volumic deformation of granular piles during continuous load in the gravity field (Staron, Vilotte, & Radjai 2002). Far before
Wavelet denoising of gravity gradiometry data Julio Cesar S. O. Lyrio*
Wavelet denoising of gravity gradiometry data Julio Cesar S. O. Lyrio* Gravity and Magnetic an automatic 1D wavelet filtering technique, specially designed to process gravity gradiometry data. The method uses compactly supported orthonormal wavelets that selectively filter out localized high
Canonical quantization of a minisuperspace model for gravity using self-dual variables
T. Thiemann
1999-10-04T23:59:59.000Z
The present article summarizes the work of the papers \\cite{1} dealing with the quantization of pure gravity and gravity coupled to a Maxwell field and a cosmological constant in presence of spherical symmetry. The class of models presented is intended as an interesting testing ground for the quantization of full 3+1 gravity. We are working in Ashtekar's self-dual representation.
Paris-Sud XI, Université de
Gravity wave turbulence revealed by horizontal vibrations of the container B. Issenmann and E: December 20, 2012) We experimentally study the role of the forcing on gravity-capillary wave turbulence that the frequency power-law exponent of the gravity wave spectrum depends on the forcing parameters. By horizontally
Investigating Commercial Cellulase Performances Toward Specific...
Broader source: All U.S. Department of Energy (DOE) Office Webpages (Extended Search)
Commercial Cellulase Performances Toward Specific Biomass Recalcitrance Factors Using Reference Substrates. Investigating Commercial Cellulase Performances Toward Specific Biomass...
Quantum-Gravity Fluctuations and the Black-Hole Temperature
Hod, Shahar
2015-01-01T23:59:59.000Z
Bekenstein has put forward the idea that, in a quantum theory of gravity, a black hole should have a discrete energy spectrum with concomitant discrete line emission. The quantized black-hole radiation spectrum is expected to be very different from Hawking's semi-classical prediction of a thermal black-hole radiation spectrum. One naturally wonders: Is it possible to reconcile the {\\it discrete} quantum spectrum suggested by Bekenstein with the {\\it continuous} semi-classical spectrum suggested by Hawking ? In order to address this fundamental question, in this essay we shall consider the zero-point quantum-gravity fluctuations of the black-hole spacetime. In a quantum theory of gravity, these spacetime fluctuations are closely related to the characteristic gravitational resonances of the corresponding black-hole spacetime. Assuming that the energy of the black-hole radiation stems from these zero-point quantum-gravity fluctuations of the black-hole spacetime, we derive the effective temperature of the quanti...
Extra force in Kaluza-Klein gravity theory
W. B. Belayev
2007-06-18T23:59:59.000Z
In induced matter Kaluza-Klein gravity theory the solution of the dynamics equations for the test particle on null path leads to additional force in four-dimensional space-time. We find such force from five-dimensional geodesic line equations and apply this approach to analysis of the asymmetrically warped space-time.
On the q-quantum gravity loop algebra
Seth Major
2008-02-19T23:59:59.000Z
A class of deformations of the q-quantum gravity loop algebra is shown to be incompatible with the combinatorics of Temperley-Lieb recoupling theory with deformation parameter at a root of unity. This incompatibility appears to extend to more general deformation parameters.
Emergent/Quantum Gravity: Macro/Micro Structures of Spacetime
B. L. Hu
2009-03-04T23:59:59.000Z
Emergent gravity views spacetime as an entity emergent from a more complete theory of interacting fundamental constituents valid at much finer resolution or higher energies, usually assumed to be above the Planck energy. In this view general relativity is an effective theory valid only at long wavelengths and low energies. For any presumed known theory for the microscopic structure of spacetime, we describe common tasks of emergent gravity (`top-down'), namely, identifying the conditions and processes or mechanisms whereby the familiar macroscopic spacetime emerges with high probability and reasonable robustness. Going in the opposite direction (`bottom-up') is the task of quantum gravity, i.e., finding a theory for the microscopic structure of spacetime, which, in this new view, cannot come from quantizing the metric or connection forms because they are the collective variables which are meaningful only for the macroscopic theory, i.e., general relativity. We suggest pathways to move `up' (in energy) from the given macroscopic conditions of classical gravity and quantum field theory to the domain closer to the micro-macro interface where spacetime emerged and places to look for clues or tell-tale signs at low energy where one could infer indirectly some salient features of the micro-structure of spacetime.
GRAVITY DRIVEN SHALLOW WATER MODELS FOR ARBITRARY TOPOGRAPHY
Blömker, Dirk
GRAVITY DRIVEN SHALLOW WATER MODELS FOR ARBITRARY TOPOGRAPHY FRANC¸OIS BOUCHUT AND MICHAEL over a general topography. A first model is valid for small slope variation, i.e. small curvature, and a second model is valid for arbitrary topography. In both cases no particular assumption is made
Einstein static Universe in hybrid metric-Palatini gravity
Christian G. Boehmer; Francisco S. N. Lobo; Nicola Tamanini
2015-02-18T23:59:59.000Z
Hybrid metric-Palatini gravity is a recent and novel approach to modified theories of gravity, which consists of adding to the metric Einstein-Hilbert Lagrangian an f(R) term constructed a la Palatini. It was shown that the theory passes local tests even if the scalar field is very light, and thus implies the existence of a long-range scalar field, which is able to modify the dynamics in galactic and cosmological scales, but leaves the Solar System unaffected. In this work, motivated by the possibility that the Universe may have started out in an asymptotically Einstein static state in the inflationary universe context, we analyse the stability of the Einstein static Universe by considering linear homogeneous perturbations in the respective dynamically equivalent scalar-tensor representation of hybrid metric-Palatini gravity. Considering linear homogeneous perturbations, the stability regions of the Einstein static universe are parametrized by the first and second derivatives of the scalar potential, and it is explicitly shown that a large class of stable solutions exists in the respective parameter space, in the context of hybrid metric-Palatini gravity.
Deformed Reissner-Nordstrom solutions in noncommutative gravity
Mukherjee, Pradip [Department of Physics, Presidency College, 86/1 College Street, Kolkata-700073, West Bengal (India); Saha, Anirban [Department of Physics, Sovarani Memorial College, Jagatballavpur, Howrah-711 408, West Bengal (India)
2008-03-15T23:59:59.000Z
The leading order corrections to Reissner-Nordstrom solutions of the Einstein's equations on noncommutative spacetime have been worked out based on a noncommutative gauge theory of gravity. From the corrected metric the horizons have been derived and the curvature scalar is also computed. The introduction of noncommutativity leads to the removal of the coordinate singularities.
3D Quantum Gravity and Effective Noncommutative Quantum Field Theory
Freidel, Laurent; Livine, Etera R. [Perimeter Institute, 31 Caroline Street, North Waterloo, Ontario N2L 2Y5, Canada, and Laboratoire de Physique, ENS Lyon, CNRS UMR 5672, 46 Allee d'Italie, 69364 Lyon Cedex 07 (France)
2006-06-09T23:59:59.000Z
We show that the effective dynamics of matter fields coupled to 3D quantum gravity is described after integration over the gravitational degrees of freedom by a braided noncommutative quantum field theory symmetric under a {kappa} deformation of the Poincare group.
Free energy of topologically massive gravity and flat space holography
Daniel Grumiller; Wout Merbis
2015-09-28T23:59:59.000Z
We calculate the free energy from the on-shell action for topologically massive gravity with negative and vanishing cosmological constant, thereby providing a first principles derivation of the free energy of BTZ black holes and flat space cosmologies. We summarize related recent checks of flat space holography.
Free energy of topologically massive gravity and flat space holography
Grumiller, Daniel
2015-01-01T23:59:59.000Z
We calculate the free energy from the on-shell action for topologically massive gravity with negative and vanishing cosmological constant, thereby providing a first principles derivation of the free energy of BTZ black holes and flat space cosmologies. We summarize related recent checks of flat space holography.
Constraints on massive gravity theory from big bang nucleosynthesis
G. Lambiase
2012-08-27T23:59:59.000Z
The massive gravity cosmology is studied in the scenario of big bang nucleosynthesis. By making use of current bounds on the deviation from the fractional mass, we derive the constraints on the free parameters of the theory. The cosmological consequences of the model are also discussed in the framework of the PAMELA experiment.
Testing gravity with halo density profiles observed through gravitational lensing
Narikawa, Tatsuya; Yamamoto, Kazuhiro, E-mail: narikawa@theo.phys.sci.hiroshima-u.ac.jp, E-mail: kazuhiro@hiroshima-u.ac.jp [Department of Physical Science, Hiroshima University, Higashi-Hiroshima 739-8526 (Japan)
2012-05-01T23:59:59.000Z
We present a new test of the modified gravity endowed with the Vainshtein mechanism with the density profile of a galaxy cluster halo observed through gravitational lensing. A scalar degree of freedom in the galileon modified gravity is screened by the Vainshtein mechanism to recover Newtonian gravity in high-density regions, however it might not be completely hidden on the outer side of a cluster of galaxies. Then the modified gravity might yield an observational signature in a surface mass density of a cluster of galaxies measured through gravitational lensing, since the scalar field could contribute to the lensing potential. We investigate how the transition in the Vainshtein mechanism affects the surface mass density observed through gravitational lensing, assuming that the density profile of a cluster of galaxies follows the original Navarro-Frenk-White (NFW) profile, the generalized NFW profile and the Einasto profile. We compare the theoretical predictions with observational results of the surface mass density reported recently by other researchers. We obtain constraints on the amplitude and the typical scale of the transition in the Vainshtein mechanism in a subclass of the generalized galileon model.
The Unified Theory - Electricity, Magnetism, Gravity and Mechanics
Pretterebner Julius
1999-08-12T23:59:59.000Z
This article shows the relations between the electricity, magnetism, gravity and mechanics by presenting an existing hidden structure in the Maxwell equations. This hidden structure allows to discover the classical physic from a new point of view leading to the unified theory (UT).
Gauge/Gravity Theory with Running Dilaton and Running Axion
Girma Hailu
2007-12-27T23:59:59.000Z
We present a new gauge/gravity duality construction of the Klebanov-Strassler throat which takes corrections to the anomalous mass dimension proposed in [1] into account on the gauge theory side and both the dilaton and the axion run on the gravity side. The corresponding supergravity solutions are found using equations for type IIB flows with N=1 supersymmetry obtained in [2]. We find that magnetic couplings of the axion to D7-branes filling 4-d spacetime and wrapping 4-cycles at locations of duality transitions and invisible Dirac 8-branes whose worldvolume emanates from the worldvolume of the D7-branes are the sources for the runnings of the dilaton and the axion. Our construction provides the first explicit example of a gauge/gravity duality mapping with a running dilaton or a running axion which is an important component towards finding gravity duals to gauge theories with physically more interesting renormalization group flows such as pure confining gauge theories in four dimensions. The D7-branes also serve as gravitational source for Seiberg duality transitions. The supergravity background has distinct features which could be useful for constructing cosmological models and studying possibilities for probing stringy signatures from the early universe.
Granular physics in low-gravity environments using DEM
G. Tancredi; A. Maciel; L. Heredia; P. Richeri; S. Nesmachnow
2011-11-26T23:59:59.000Z
Granular materials of different sizes are present on the surface of several atmosphere-less Solar System bodies. The phenomena related to granular materials have been studied in the framework of the discipline called Granular Physics; that has been studied experimentally in the laboratory and, in the last decades, by performing numerical simulations. The Discrete Element Method simulates the mechanical behavior of a media formed by a set of particles which interact through their contact points. The difficulty in reproducing vacuum and low-gravity environments makes numerical simulations the most promising technique in the study of granular media under these conditions. In this work, relevant processes in minor bodies of the Solar System are studied using the Discrete Element Method. Results of simulations of size segregation in low-gravity environments in the cases of the asteroids Eros and Itokawa are presented. The segregation of particles with different densities was analysed, in particular, the case of comet P/Hartley 2. The surface shaking in these different gravity environments could produce the ejection of particles from the surface at very low relative velocities. The shaking causing the above processes is due to: impacts, explosions like the release of energy by the liberation of internal stresses or the re accommodation of material. Simulations of the passage of impact-induced seismic waves through a granular medium were also performed. We present several applications of the Discrete Element Methods for the study of the physical evolution of agglomerates of rocks under low-gravity environments.
Kac-Moody algebras in gravity and M-theories
Houart, Laurent [Service de Physique Theorique et Mathematique, Universite Libre de Bruxelles, Campus Plaine C.P. 231, Boulevard du Triomphe, B-1050 Brussels (Belgium); International Solvay Instiitutes, Campus Plaine C.P. 231, Boulevard du Triomphe, B-1050 Brussels (Belgium)
2006-06-19T23:59:59.000Z
The formulation of gravity and M-theories as very-extended Kac-Moody invariant theories is reviewed. Exact solutions describing intersecting extremal brane configurations smeared in all directions but one are presented. The intersection rules characterising these solutions are neatly encoded in the algebra. The existence of dualities for all G +++ and their group theoretical-origin are discussed.
Programme Specification 1. General Information
Subramanian, Sriram
, administrative and practical skills required in exhibition making. Able to: C. Professionalism C1. Take Institution Royal College of Art Professional Accreditation N/A Qualifications Framework Level 7 Credit Value as competent and #12;Programme Specification 2/10 responsible professionals, equipped with the knowledge
PROGRAMME SPECIFICATION Programme title: Statistics
Guillas, Serge
in statistical theory and applications which enables graduates to enter specialist employment or academic in statistical computing and communication are assessed by coursework only. The summer project is assessedPROGRAMME SPECIFICATION Programme title: Statistics Final award (BSc, MA etc): (where stopping off
ProductSpecifications Thermo Scientific
Short, Daniel
ProductSpecifications Thermo Scientific Niton XL3t GOLDD+ XRF Analyzer The Thermo Scientific Niton to provide you with a solution to your most difficult analytical requirements. Thermo Scientific Niton XL3t-qualityperformanceinahandheldinstrument,including tramp/trace elements Breakthrough Technologies The GOLDD Advantage The Thermo Scientific Niton XL3t
ProductSpecifications Thermo Scientific
Peraire, Jaime
ProductSpecifications Thermo Scientific CellomicsArrayScan VTI HCS Reader The Thermo Scientific info.cellularimaging@thermofisher.com www.thermo.com/cellomics and Cellular Imaging Europe: +44 118 988 and filters available Integrated Software Features · Thermo Scientific Cellomics iQ - High Content intelligent
Temporal Specifications with Accumulative Values
Boker, Udi
Temporal Specifications with Accumulative Values Udi Boker, Krishnendu Chatterjee, Thomas A the accumulation of values along a computation. It is either the accumulated summation, as with the energy objectives, or the accumulated average, as with the mean-payoff objectives. We investigate the extension
Cartan gravity, matter fields, and the gauge principle
Westman, Hans F., E-mail: hwestman74@gmail.com [Imperial College Theoretical Physics, Huxley Building, London, SW7 2AZ (United Kingdom); Zlosnik, Tom G., E-mail: t.zlosnik@imperial.ac.uk [Instituto de Física Fundamental, CSIC, Serrano 113-B, 28006 Madrid (Spain)
2013-07-15T23:59:59.000Z
Gravity is commonly thought of as one of the four force fields in nature. However, in standard formulations its mathematical structure is rather different from the YangMills fields of particle physics that govern the electromagnetic, weak, and strong interactions. This paper explores this dissonance with particular focus on how gravity couples to matter from the perspective of the Cartan-geometric formulation of gravity. There the gravitational field is represented by a pair of variables: (1) a contact vector V{sup A} which is geometrically visualized as the contact point between the spacetime manifold and a model spacetime being rolled on top of it, and (2) a gauge connection A{sub ?}{sup AB}, here taken to be valued in the Lie algebra of SO(2,3) or SO(1,4), which mathematically determines how much the model spacetime is rotated when rolled. By insisting on two principles, the gauge principle and polynomial simplicity, we shall show how one can reformulate matter field actions in a way that is harmonious with Cartans geometric construction. This yields a formulation of all matter fields in terms of first order partial differential equations. We show in detail how the standard second order formulation can be recovered. In particular, the Hodge dual, which characterizes the structure of bosonic field equations, pops up automatically. Furthermore, the energymomentum and spin-density three-forms are naturally combined into a single object here denoted the spin-energymomentum three-form. Finally, we highlight a peculiarity in the mathematical structure of our first-order formulation of YangMills fields. This suggests a way to unify a U(1) gauge field with gravity into a SO(1,5)-valued gauge field using a natural generalization of Cartan geometry in which the larger symmetry group is spontaneously broken down to SO(1,3)×U(1). The coupling of this unified theory to matter fields and possible extensions to non-Abelian gauge fields are left as open questions. -- Highlights: Develops Cartan gravity to include matter fields. Coupling to gravity is done using the standard gauge prescription. Matter actions are manifestly polynomial in all field variables. Standard equations recovered on-shell for scalar, spinor and YangMills fields. Unification of a U(1) field with gravity based on the orthogonal group SO(1,5)
Gravity monitoring of CO2 movement during sequestration: Model studies
Gasperikova, E.; Hoversten, G.M.
2008-07-15T23:59:59.000Z
We examine the relative merits of gravity measurements as a monitoring tool for geological CO{sub 2} sequestration in three different modeling scenarios. The first is a combined CO{sub 2} enhanced oil recovery (EOR) and sequestration in a producing oil field, the second is sequestration in a brine formation, and the third is for a coalbed methane formation. EOR/sequestration petroleum reservoirs have relatively thin injection intervals with multiple fluid components (oil, hydrocarbon gas, brine, and CO{sub 2}), whereas brine formations usually have much thicker injection intervals and only two components (brine and CO{sub 2}). Coal formations undergoing methane extraction tend to be thin (3-10 m), but shallow compared to either EOR or brine formations. The injection of CO{sub 2} into the oil reservoir produced a bulk density decrease in the reservoir. The spatial pattern of the change in the vertical component of gravity (G{sub z}) is directly correlated with the net change in reservoir density. Furthermore, time-lapse changes in the borehole G{sub z} clearly identified the vertical section of the reservoir where fluid saturations are changing. The CO{sub 2}-brine front, on the order of 1 km within a 20 m thick brine formation at 1900 m depth, with 30% CO{sub 2} and 70% brine saturations, respectively, produced a -10 Gal surface gravity anomaly. Such anomaly would be detectable in the field. The amount of CO{sub 2} in a coalbed methane test scenario did not produce a large enough surface gravity response; however, we would expect that for an industrial size injection, the surface gravity response would be measurable. Gravity inversions in all three scenarios illustrated that the general position of density changes caused by CO{sub 2} can be recovered, but not the absolute value of the change. Analysis of the spatial resolution and detectability limits shows that gravity measurements could, under certain circumstances, be used as a lower-cost alternative to seismic measurements.
Multi-gravity separator: an alternate gravity concentrator to process coal fines
Majumder, A.K.; Bhoi, K.S.; Barnwal, J.P. [Regional Research Laboratories, Bhopal (India)
2007-08-15T23:59:59.000Z
The multi-gravity separator (MGS) is a novel piece of equipment for the separation of fine and ultra-fine minerals. However, the published literature does not demonstrate its use in the separation of coal fines. Therefore, an attempt was made to study the effects of different process variables on the performance of an MGS for the beneficiation of coal fines. The results obtained from this study revealed that among the parameters studied, drum rotation and feed solids concentration play dominating roles in controlling the yield and ash content of the clean coal. Mathematical modeling equations that correlate the variables studied and the yield and ash contents of the clean coal were developed to predict the performance of an MGS under different operating and design conditions. The entire exercise revealed that the MGS could produce a clean coal with an ash content of 14.67% and a yield of 71.23% from a feed coal having an ash content of 24.61 %.
Logarithmic Singularities of Specific Heat and Related Properties of Liquid $^4He$ Near $?-$Point
Simanta C.; Yatendra S. Jain
2006-12-12T23:59:59.000Z
The singularity of specific heat ($C_p$) and related properties (viz. thermal expansion coefficient, compressibility and pressure coefficient) of liquid $^4He$ at $\\lambda-$point is studied and the accuracy of its logarithmic nature as concluded for the first time from a microscopic theory (cond-mat/0606571) of a system of interacting bosons is examined. A very good agreement between the results of this theory and experiments concludes that singularity is intrinsically logarithmic. However, as shown by other studies, weak effects arising from earth's gravity and small sample size round it off and $C_p$ assumes asymptotic nature near $T_{\\lambda}$.
Chromosome specific repetitive DNA sequences
Moyzis, Robert K. (Los Alamos, NM); Meyne, Julianne (Los Alamos, NM)
1991-01-01T23:59:59.000Z
A method is provided for determining specific nucleotide sequences useful in forming a probe which can identify specific chromosomes, preferably through in situ hybridization within the cell itself. In one embodiment, chromosome preferential nucleotide sequences are first determined from a library of recombinant DNA clones having families of repetitive sequences. Library clones are identified with a low homology with a sequence of repetitive DNA families to which the first clones respectively belong and variant sequences are then identified by selecting clones having a pattern of hybridization with genomic DNA dissimilar to the hybridization pattern shown by the respective families. In another embodiment, variant sequences are selected from a sequence of a known repetitive DNA family. The selected variant sequence is classified as chromosome specific, chromosome preferential, or chromosome nonspecific. Sequences which are classified as chromosome preferential are further sequenced and regions are identified having a low homology with other regions of the chromosome preferential sequence or with known sequences of other family me This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).
A natural approach to extended Newtonian gravity: tests and predictions across astrophysical scales
S. Mendoza; X. Hernandez; J. C. Hidalgo; T. Bernal
2010-09-10T23:59:59.000Z
In the pursuit of a general formulation for a modified gravitational theory at the non-relativistic level and as an alternative to the dark matter hypothesis, we construct a model valid over a wide variety of astrophysical scales. Through the inclusion of Milgrom's acceleration constant into a gravitational theory, we show that very general formulas can be constructed for the acceleration felt by a particle. Dimensional analysis shows that this inclusion naturally leads to the appearance of a mass-length scale in gravity, breaking its scale invariance. A particular form of the modified gravitational force is constructed and tested for consistency with observations over a wide range of astrophysical environments, from solar system to extragalactic scales. We show that over any limited range of physical parameters, which define a specific class of astrophysical objects, the dispersion velocity of a system must be a power law of its mass and size. These powers appear linked together through a natural constraint relation of the theory. This yields a generalised gravitational equilibrium relation valid for all astrophysical systems. A general scheme for treating spherical symmetrical density distributions is presented, which in particular shows that the fundamental plane of elliptical galaxies, the Newtonian virial equilibrium, the Tully-Fisher and the Faber-Jackson relations, as well as the scalings observed in local dwarf spheroidal galaxies, are nothing but particular cases of that relation when applied to the appropriate mass-length scales. We discuss the implications of this approach for a modified theory of gravity and emphasise the advantages of working with the force, instead of altering Newton's second law of motion, in the formulation of a gravitational theory.
Central Solenoid Insert Technical Specification
Martovetsky, Nicolai N [ORNL; Smirnov, Alexandre [ORNL
2011-09-01T23:59:59.000Z
The US ITER Project Office (USIPO) is responsible for the ITER central solenoid (CS) contribution to the ITER project. The Central Solenoid Insert (CSI) project will allow ITER validation the appropriate lengths of the conductors to be used in the full-scale CS coils under relevant conditions. The ITER Program plans to build and test a CSI to verify the performance of the CS conductor. The CSI is a one-layer solenoid with an inner diameter of 1.48 m and a height of 4.45 m between electric terminal ends. The coil weight with the terminals is approximately 820 kg without insulation. The major goal of the CSI is to measure the temperature margin of the CS under the ITER direct current (DC) operating conditions, including determining sensitivity to load cycles. Performance of the joints, ramp rate sensitivity, and stability against thermal or electromagnetic disturbances, electrical insulation, losses, and instrumentation are addressed separately and therefore are not major goals in this project. However, losses and joint performance will be tested during the CSI testing campaign. The USIPO will build the CSI that will be tested at the Central Solenoid Model Coil (CSMC) Test Facility at the Japan Atomic Energy Agency (JAEA), Naka, Japan. The industrial vendors (the Suppliers) will report to the USIPO (the Company). All approvals to proceed will be issued by the Company, which in some cases, as specified in this document, will also require the approval of the ITER Organization. Responsibilities and obligations will be covered by respective contracts between the USIPO, called Company interchangeably, and the industrial Prime Contractors, called Suppliers. Different stages of work may be performed by more than one Prime Contractor, as described in this specification. Technical requirements of the contract between the Company and the Prime Contractor will be covered by the Fabrication Specifications developed by the Prime Contractor based on this document and approved by the Company and ITER. The Fabrication Specifications may reflect some national requirements and regulations that are not fully provided here. This document presents the ITER CSI specifications.
Project X functional requirements specification
Holmes, S.D.; Henderson, S.D.; Kephart, R.; Kerby, J.; Kourbanis, I.; Lebedev, V.; Mishra, S.; Nagaitsev, S.; Solyak, N.; Tschirhart, R.; /Fermilab
2012-05-01T23:59:59.000Z
Project X is a multi-megawatt proton facility being developed to support a world-leading program in Intensity Frontier physics at Fermilab. The facility is designed to support programs in elementary particle and nuclear physics, with possible applications to nuclear energy research. A Functional Requirements Specification has been developed in order to establish performance criteria for the Project X complex in support of these multiple missions, and to assure that the facility is designed with sufficient upgrade capability to provide U.S. leadership for many decades to come. This paper will briefly review the previously described Functional Requirements, and then discuss their recent evolution.
Pure Geometric Field Theory: Description of Gravity and Material Distribution
M. I. Wanas; Nabil L. Youssef; W. El Hanafy
2015-03-31T23:59:59.000Z
A field theory is constructed in the context of parameterized absolute parallelism\\linebreak geometry. The theory is shown to be a pure gravity one. It is capable of describing the gravitational field and a material distribution in terms of the geometric structure of the geometry used (the parallelization vector fields). Three tools are used to attribute physical properties to the geometric objects admitted by the theory. Poisson and Laplace equations are obtained in the linearized version of the theory. The spherically symmetric solution of the theory, in free space, is found to coincide with the Schwarzschild exterior solution of the general theory of relativity. The theory respects the weak equivalence principle in free space only. Gravity and material distribution are not minimally coupled.
Fourth order gravity: equations, history, and applications to cosmology
H. -J. Schmidt
2006-03-25T23:59:59.000Z
The field equations following from a Lagrangian L(R) will be deduced and solved for special cases. If L is a non-linear function of the curvature scalar, then these equations are of fourth order in the metric. In the introduction we present the history of these equations beginning with the paper of H. Weyl from 1918, who first discussed them as alternative to Einstein's theory. In the third part, we give details about the cosmic no hair theorem, i.e., the details how within fourth order gravity with L= R + R^2 the inflationary phase of cosmic evolution turns out to be a transient attractor. Finally, the Bicknell theorem, i.e. the conformal relation from fourth order gravity to scalar-tensor theory, will be shortly presented.
Climate variability according to triple saros gravity cycles
William R. Livingston
2013-06-03T23:59:59.000Z
I describe a climate model which corresponds directly to eclipse cycles. The theory is based upon a similarity between the 54 year triple saros eclipse period and the periodicity of drought. I argue that eclipse shadows are an indication of gravity cycles, and that variable lunar gravitation is the most significant aspect of the eclipse process. I reinforce the idea that lunar gravitational forcing has a profound effect on the water vapor in Earth's atmosphere, and can affect the density and location of clouds. I explore the possibility that decadal variability of ocean surface levels may be explained by triple saros gravity cycles. I point out that lunar gravitation was excluded from the most significant climate report of 2007, and that climate data contradictions have been overlooked by researchers. I focus on the value of data that has not been aggregated into global averages. I touch upon the history of global warming, and I offer predictions based upon 54 year climate periodicity.
Trapping and aerogelation of nanoparticles in negative gravity hydrocarbon flames
Chakrabarty, Rajan K., E-mail: rajan.chakrabarty@gmail.com [Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130 (United States); Laboratory for Aerosol Science, Spectroscopy, and Optics, Desert Research Institute, Nevada System of Higher Education, Reno, Nevada 89512 (United States); Novosselov, Igor V. [Department of Mechanical Engineering, University of Washington, Seattle, Washington 98195 (United States); Enertechnix Inc., Maple Valley, Washington 98068 (United States); Beres, Nicholas D.; Moosmüller, Hans [Laboratory for Aerosol Science, Spectroscopy, and Optics, Desert Research Institute, Nevada System of Higher Education, Reno, Nevada 89512 (United States); Sorensen, Christopher M. [Condensed Matter Laboratory, Department of Physics, Kansas State University, Manhattan, Kansas 66506 (United States); Stipe, Christopher B. [TSI Incorporated, 500 Cardigan Rd, Shoreview, Minnesota 55126 (United States)
2014-06-16T23:59:59.000Z
We report the experimental realization of continuous carbon aerogel production using a flame aerosol reactor by operating it in negative gravity (?g; up-side-down configuration). Buoyancy opposes the fuel and air flow forces in ?g, which eliminates convectional outflow of nanoparticles from the flame and traps them in a distinctive non-tipping, flicker-free, cylindrical flame body, where they grow to millimeter-size aerogel particles and gravitationally fall out. Computational fluid dynamics simulations show that a closed-loop recirculation zone is set up in ?g flames, which reduces the time to gel for nanoparticles by ?10{sup 6}?s, compared to positive gravity (upward rising) flames. Our results open up new possibilities of one-step gas-phase synthesis of a wide variety of aerogels on an industrial scale.
Induced Matter Brane Gravity and Einstein Static Universe
Y. Heydarzade; F. Darabi
2015-04-21T23:59:59.000Z
We investigate stability of the Einstein static universe against the scalar, vector and tensor perturbations in the context of induced matter brane gravity. It is shown that in the framework of this model, the Einstein static universe has a positive spatial curvature. In contrast to the classical general relativity, it is found that a stable Einstein static universe against the scalar perturbations does exist provided that the variation of time dependent geometrical equation of state parameter is proportional to the minus of the variation of the scale factor, $\\delta \\omega_{g}(t)=-C\\delta a(t)$. We obtain neutral stability against the vector perturbations, and the stability against the tensor perturbations is guaranteed due to the positivity of the spatial curvature of the Einstein static universe in induced matter brane gravity.
Evaluation of an Impulse Gravity Generator Based Beamed Propulsion Concept
Giovanni Modanese; Chris Y. Taylor
2002-09-05T23:59:59.000Z
This paper analyzes the suitability of a beamed propulsion concept having properties consistent with the impulse gravity generator described by Podkletnov et al. [physics/0108005]. The use of this propulsion concept for orbital maneuver, Earth-to-orbit, interplanetary, and interstellar applications based on presently available experimental results and theory is considered, and areas for future research needed to better characterize this phenomenon are discussed. A beam of radiation or particles with the properties described for the impulse gravity generator would appear to be an excellent candidate for use in beamed spacecraft propulsion. Besides the usual benefits of beamed propulsion, it would not need sails or other special spacecraft components to function, could safely provide high accelerations to delicate components, and might operate at higher efficiencies than other beamed propulsion concepts.
Holographic renormalization and anisotropic black branes in higher curvature gravity
Viktor Jahnke; Anderson Seigo Misobuchi; Diego Trancanelli
2014-12-30T23:59:59.000Z
We consider five-dimensional AdS-axion-dilaton gravity with a Gauss-Bonnet term and find a solution of the equations of motion which corresponds to a black brane exhibiting a spatial anisotropy, with the source of the anisotropy being an axion field linear in one of the horizon coordinates. Our solution is static, regular everywhere on and outside the horizon, and asymptotically AdS. It is analytic and valid in a small anisotropy expansion, but fully non-perturbative in the Gauss-Bonnet coupling. We discuss various features of this solution and use it as a gravity dual to a strongly coupled anisotropic plasma with two independent central charges, $a\
Modelling gravity on a hyper-cubic lattice
Tate, Kyle
2012-01-01T23:59:59.000Z
We present an elegant and simple dynamical model of symmetric, non-degenerate (n x n) matrices of fixed signature defined on a n-dimensional hyper-cubic lattice with nearest-neighbor interactions. We show how this model is related to General Relativity, and discuss multiple ways in which it can be useful for studying gravity, both classical and quantum. In particular, we show that the dynamics of the model when all matrices are close to the identity corresponds exactly to a finite-difference discretization of weak-field gravity in harmonic gauge. We also show that the action which defines the full dynamics of the model corresponds to the Einstein-Hilbert action to leading order in the lattice spacing, and use this observation to define a lattice analogue of the Ricci scalar and Einstein tensor. Finally, we perform a mean-field analysis of the statistical mechanics of this model.
Cloud of strings for radiating black holes in Lovelock gravity
Sushant G. Ghosh; Sunil D. Maharaj
2014-09-28T23:59:59.000Z
We present exact spherically symmetric null dust solutions in the third order Lovelock gravity with a string cloud background in arbitrary $N$ dimensions,. This represents radiating black holes and generalizes the well known Vaidya solution to Lovelock gravity with a string cloud in the background. We also discuss the energy conditions and horizon structures, and explicitly bring out the effect of the string clouds on the horizon structure of black hole solutions for the higher dimensional general relativity and Einstein-Gauss-Bonnet theories. It turns out that the presence of the coupling constant of the Gauss-Bonnet terms and/or background string clouds completely changes the structure of the horizon and this may lead to a naked singularity. We recover known spherically symmetric radiating models as well as static black holes in the appropriate limits.
f(R) Gravity, relic coherent gravitons and optical chaos
Lawrence B. Crowell; Christian Corda
2014-02-19T23:59:59.000Z
We discuss the production of massive relic coherent gravitons in a particular class of f(R) gravity which arises from string theory and their possible imprint in Cosmic Microwave Background. In fact, in the very early universe these relic gravitons could have acted as slow gravity waves. They may have then acted to focus the geodesics of radiation and matter. Therefore, their imprint on the later evolution of the universe could appear as filaments and domain wall in the Universe today. In that case, the effect on Cosmic Microwave Background should be analogous to the effect of water waves, which, in focusing light, create optical caustics which are commonly seen on the bottom of swimming pools. We analyze this important issue by showing how relic massive GWs perturb the trajectories of Cosmic Microwave Background photons (gravitational lensing by relic GWs). The consequence of the type of physics discussed is outlined by illustrating an amplification of what might be called optical chaos.
Energy and stability analysis of mimetic-f(R) gravity
Haghani, Zahra; Shiravand, Maryam
2015-01-01T23:59:59.000Z
The energy conditions of mimetic-$f(R)$ gravity theory, together with the Dolgov-Kawasaki instability will be analysed. It will be shown that the condition for the stability of the theory against Dolgov-Kawasaki is equivalent to the standard $f(R)$ gravity theory. We will also show that the exact de Sitter solution for the theory can only be obtained by an exponential form for the function $f(R)$. The Brans-Dicke equivalence of the theory is also discussed in more details. We will obtain the parameter space of the theory in an exponential and power law forms of $f(R)$, for violating the strong energy condition while satisfying the weak, null and dominant energy conditions.
CP-safe Gravity Mediation and Muon g-2
Sho Iwamoto; Tsutomu T. Yanagida; Norimi Yokozaki
2015-02-03T23:59:59.000Z
We propose a CP-safe gravity mediation model, where the phases of the Higgs B parameter, scalar trilinear couplings and gaugino mass parameters are all aligned. Since all dangerous CP violating phases are suppressed, we are now safe to consider low-energy SUSY scenarios. As an application, we consider a gravity mediation model explaining the observed muon $g-2$ anomaly. The CP-safe property originates in two simple assumptions: SUSY breaking in the K\\"ahler potential and a shift symmetry of a SUSY breaking field $Z$. As a result of the shift symmetry, the imaginary part of $Z$ behaves as a QCD axion, leading to an intriguing possibility: the strong CP problem in QCD and the SUSY CP problem are solved simultaneously.
Clouds of strings in third-order Lovelock gravity
Sushant G. Ghosh; Uma Papnoi; Sunil D. Maharaj
2014-08-20T23:59:59.000Z
Lovelock theory is a natural extension of the Einstein theory of general relativity to higher dimensions in which the first and second orders correspond, respectively, to general relativity and Einstein-Gauss-Bonnet gravity. We present exact black hole solutions of $D\\geq 4$-dimensional spacetime for first-, second-, and third-order Lovelock gravities in a string cloud background. Further, we compute the mass, temperature, and entropy of black hole solutions for the higher-dimensional general relativity and Einstein-Gauss-Bonnet theories and also perform thermodynamic stability of black holes. It turns out that the presence of the Gauss-Bonnet term and/or background string cloud completely changes the black hole thermodynamics. Interestingly, the entropy of a black hole is unaffected due to a background string cloud. We rediscover several known spherically symmetric black hole solutions in the appropriate limits.
Is Holographic Entropy and Gravity the result of Quantum Mechanics?
Joakim Munkhammar
2010-03-09T23:59:59.000Z
In this paper we suggest a connection between quantum mechanics and Verlinde's recently proposed entropic force theory for the laws of Newton. We propose an entropy based on the quantum mechanical probability density distribution. With the assumption that the holographic principle holds we propose that our suggested quantum entropy generalizes the Bekenstein entropy used by Verlinde in his approach. Based on this assumption we suggest that Verlinde's entropic theory of gravity has a quantum mechanical origin. We establish a reformulation of the Newtonian potential for gravity based on this quantum mechanical entropy. We also discuss the notion of observation and the correspondence to classical physics. Finally we give a discussion, a number of open problems and some concluding remarks.
Giant black hole ringings induced by massive gravity
Yves Decanini; Antoine Folacci; Mohamed Ould El Hadj
2014-01-01T23:59:59.000Z
A distorted black hole radiates gravitational waves in order to settle down in one of the geometries permitted by the no-hair theorem. During that relaxation phase, a characteristic damped ringing is generated. It can be theoretically constructed from the black hole quasinormal frequencies (which govern its oscillating behavior and its decay) and from the associated excitation factors (which determine intrinsically its amplitude) by carefully taking into account the source of the distortion. Here, by considering the Schwarzschild black hole in the framework of massive gravity, we show that the excitation factors have an unexpected strong resonant behavior leading to giant ringings which are, moreover, slowly decaying. Such extraordinary black hole ringings could be observed by the next generations of gravitational wave detectors and allow us to test the various massive gravity theories or their absence could be used to impose strong constraints on the graviton mass.
Weak Gravity Strongly Constrains Large-Field Axion Inflation
Ben Heidenreich; Matthew Reece; Tom Rudelius
2015-06-10T23:59:59.000Z
Models of large-field inflation based on axion-like fields with shift symmetries can be simple and natural, and make a promising prediction of detectable primordial gravitational waves. The Weak Gravity Conjecture is known to constrain the simplest case in which a single axion descends from a gauge field in an extra dimension. By supplementing the Weak Gravity Conjecture with considerations of how the mass spectrum of the theory varies across the axion moduli space, we obtain more powerful constraints that apply to a variety of multi-axion theories including N-flation and alignment models. In every case that we consider, plausible assumptions lead to field ranges that cannot be parametrically larger than the Planck scale. Our results are strongly suggestive of a general inconsistency in models of large-field inflation based on axions, and possibly of a more general principle forbidding super-Planckian field ranges.
Constraints on Axion Inflation from the Weak Gravity Conjecture
Rudelius, Tom
2015-01-01T23:59:59.000Z
We derive constraints facing models of axion inflation based on decay constant alignment from a string-theoretic and quantum gravitational perspective. In particular, we investigate the prospects for alignment and `anti-alignment' of $C_4$ axion decay constants in type IIB string theory, deriving a strict no-go result in the latter case. We discuss the relationship of axion decay constants to the weak gravity conjecture and demonstrate agreement between our string-theoretic constraints and those coming from the `generalized' weak gravity conjecture. Finally, we consider a particular model of decay constant alignment in which the potential of $C_4$ axions in type IIB compactifications on a Calabi-Yau three-fold is dominated by contributions from $D7$-branes, pointing out that this model evades some of the challenges derived earlier in our paper but is highly constrained by other geometric considerations.
Weak Gravity Strongly Constrains Large-Field Axion Inflation
Heidenreich, Ben; Rudelius, Tom
2015-01-01T23:59:59.000Z
Models of large-field inflation based on axion-like fields with shift symmetries can be simple and natural, and make a promising prediction of detectable primordial gravitational waves. The Weak Gravity Conjecture is known to constrain the simplest case in which a single axion descends from a gauge field in an extra dimension. By supplementing the Weak Gravity Conjecture with considerations of how the mass spectrum of the theory varies across the axion moduli space, we obtain more powerful constraints that apply to a variety of multi-axion theories including N-flation and alignment models. In every case that we consider, plausible assumptions lead to field ranges that cannot be parametrically larger than the Planck scale. Our results are strongly suggestive of a general inconsistency in models of large-field inflation based on axions, and possibly of a more general principle forbidding super-Planckian field ranges.
Constraining f(T) gravity in the Solar System
Iorio, Lorenzo; Ruggiero, Matteo Luca
2015-01-01T23:59:59.000Z
In the framework of $f(T)$ theories of gravity, we solve the field equations for $f(T)=T+\\alpha T^{n}$, in the weak-field approximation and for spherical symmetry spacetime. Since $f(T)=T$ corresponds to Teleparallel Gravity, which is equivalent to General Relativity, the non linearity of the Lagrangian are expected to produce perturbations of the general relativistic solutions, parameterized by $\\alpha$. Hence, we use the $f(T)$ solutions to model the gravitational field of the Sun, and exploit data from accurate tracking of spacecrafts orbiting Mercury and Saturn to infer preliminary insights on what could be obtained about the model parameter $\\alpha$ and the cosmological constant $\\Lambda$. It turns out that improvements of about one-three orders with respect to the present-day constraints in the literature of magnitude seem possible.
The Weak-Coupling Limit of Simplicial Quantum Gravity
G. Thorleifsson; P. Bialas; B. Petersson
1998-12-23T23:59:59.000Z
In the weak-coupling limit, kappa_0 going to infinity, the partition function of simplicial quantum gravity is dominated by an ensemble of triangulations with the ratio N_0/N_D close to the upper kinematic limit. For a combinatorial triangulation of the D--sphere this limit is 1/D. Defining an ensemble of maximal triangulations, i.e. triangulations that have the maximal possible number of vertices for a given volume, we investigate the properties of this ensemble in three dimensions using both Monte Carlo simulations and a strong-coupling expansion of the partition function, both for pure simplicial gravity and a with a suitable modified measure. For the latter we observe a continuous phase transition to a crinkled phase and we investigate the fractal properties of this phase.
Quantizing Horava-Lifshitz gravity via causal dynamical triangulations
DOE Public Access Gateway for Energy & Science Beta (PAGES Beta)
Anderson, Christian; Carlip, Steven J.; Cooperman, Joshua H.; Ho?ava, Petr; Kommu, Rajesh K.; Zulkowski, Patrick R.
2012-02-01T23:59:59.000Z
We extend the discrete Regge action of causal dynamical triangulations to include discrete versions of the curvature squared terms appearing in the continuum action of (2+1)-dimensional projectable Horava-Lifshitz gravity. Focusing on an ensemble of spacetimes whose spacelike hypersurfaces are two-spheres, we employ Markov chain Monte Carlo simulations to study the path integral defined by this extended discrete action. We demonstrate the existence of known and novel macroscopic phases of spacetime geometry, and we present preliminary evidence for the consistency of these phases with solutions to the equations of motion of classical Horava-Lifshitz gravity. Apparently, the phase diagram contains a phase transition between a time-dependent de Sitter-like phase and a time-independent phase. We speculate that this phase transition may be understood in terms of deconfinement of the global gravitational Hamiltonian integrated over a spatial two-sphere.
Solar-System Constraints on f(R) Chameleon Gravity
Je-An Gu; Wei-Ting Lin
2011-08-08T23:59:59.000Z
We investigate the solar-system constraint on the f(R) theory of modified gravity with chameleon mechanism, where f(R) represents the deviation from general relativity in the gravity action. We obtain a stringent bound to a general, non-constant deviation function f(R): -10^{-15} 3*10^5*H0^2, by requiring the thin-shell condition in the solar system, particularly in the atmosphere of the Earth. These bounds can be conveniently utilized to test the f(R) models with given functional forms of f(R) and to obtain the constraints on the parameters therein. For demonstration we apply these bounds to several widely considered f(R) models. (H0: Hubble constant)
Collegiate Wind Competition Wind Tunnel Specifications | Department...
Wind Tunnel Specifications Collegiate Wind Competition Wind Tunnel Specifications Teams competing in the U.S. Department of Energy Collegiate Wind Competition must design a...
Independent Loop Invariants for 2+1 Gravity
R. Loll
1994-08-03T23:59:59.000Z
We identify an explicit set of complete and independent Wilson loop invariants for 2+1 gravity on a three-manifold $M=\\R\\times\\Sigma^g$, with $\\Sigma^g$ a compact oriented Riemann surface of arbitrary genus $g$. In the derivation we make use of a global cross section of the $PSU(1,1)$-principal bundle over Teichm\\"uller space given in terms of Fenchel-Nielsen coordinates.
Particlelike solutions in modified gravity: the Higgs monopole
Sandrine Schlogel; Massimiliano Rinaldi; Francois Staelens; Andre Fuzfa
2014-08-21T23:59:59.000Z
Higgs inflation has received a remarkable attention in the last few years due to its simplicity and predictive power. The key point of this model is the nonminimal coupling to gravity in unitary gauge. As such, this theory is in fact a scalar-tensor modification of gravity that needs to be studied also below the energy scales of inflation. Motivated by this goal, we study in great analytical and numerical detail the static and spherically symmetric solutions of the equations of motion in the presence of standard baryonic matter, called "Higgs monopoles" and presented in 1305.2640. These particlelike solutions may arise naturally in tensor-scalar gravity with mexican hat potential and are the only globally regular asymptotically flat solutions with finite classical energy. In the case when the parameters of the potential are taken to be the ones of the standard model, we find that the deviations from general relativity are extremely small, especially for bodies of astrophysical size and density. This allows to derive a simplified description of the monopole, for which the metric inside the spherical matter distribution can be approximated by the standard metric of general relativity. We study how the properties of these monopoles depend on the strength of the nonminimal coupling to gravity and on the baryonic mass and compactness. An important and original result is the existence of a mechanism of resonant amplification of the Higgs field inside the monopole that comes into play for large nonminimal coupling. We show that this mechanism might degenerate into divergences of the Higgs field that reveal the existence of forbidden combinations of radius and baryonic energy density.
Electric field in 3D gravity with torsion
M. Blagojevi?; B. Cvetkovi?
2008-09-01T23:59:59.000Z
It is shown that in static and spherically symmetric configurations of the system of Maxwell field coupled to 3D gravity with torsion, at least one of the Maxwell field components has to vanish. Restricting our attention to the electric sector of the theory, we find an interesting exact solution, corresponding to the azimuthal electric field. Its geometric structure is to a large extent influenced by the values of two different central charges, associated to the asymptotic AdS structure of spacetime.
Fluid/Gravity Correspondence, Second Order Transport and Gravitational Anomaly
Eugenio Megias; Francisco Pena-Benitez
2013-07-29T23:59:59.000Z
We study the transport properties of a relativistic fluid affected by chiral and gauge-gravitational anomalies. The computation is performed in the framework of the fluid/gravity correspondence for a 5 dim holographic model with Chern-Simons terms in the action. We find new anomalous and non anomalous transport coefficients, as well as new contributions to the existing ones coming from the mixed gauge-gravitational anomaly. Consequences for the shear waves dispersion relation are analyzed.
Gravity interpretation of the northern Overthrust Belt, Idaho and Wyoming
Silver, Wendy Ilene
1979-01-01T23:59:59.000Z
profiles A-A', B-8', and C-C' within the northern Overthrust Belt and the Green River Basin 45 48 17 Comparison of original structure section (top) and final interpretive structure model (bottom) for profile A-A' across the northern Overthrust Belt... 52 18 Observed and computed gravity values and fina'1 interpretive structure model for profile A-A' across the northern Overthrust Belt 54 19 Comparison of original structure section (top) and final interpretive structure model (bottom...
Tolman mass, generalized surface gravity, and entropy bounds
Abreu, Gabriel
2010-01-01T23:59:59.000Z
In any static spacetime the quasi-local Tolman mass contained within a volume can be reduced to a Gauss-like surface integral involving the flux of a suitably defined generalized surface gravity. By introducing some basic thermodynamics and invoking the Unruh effect one can then develop elementary bounds on the quasi-local entropy that are very similar in spirit to the holographic bound, and closely related to entanglement entropy.
Constraints on massive gravity theory from big bang nucleosynthesis
Lambiase, G., E-mail: lambiase@sa.infn.it [Dipartimento di Fisica 'E. R.Caianiello', Università di Salerno, 84081 Baronissi (Italy)
2012-10-01T23:59:59.000Z
The massive gravity cosmology is studied in the scenario of big bang nucleosynthesis. By making use of current bounds on the deviation from the fractional mass, we derive the constraints on the free parameters of the theory. The cosmological consequences of the model are also analyzed in the framework of the PAMELA experiment, i.e. an excess of positron events, that the conventional cosmology and particle physics cannot explain.
Multipole moments in scalar-tensor theory of gravity
George Pappas; Thomas P. Sotiriou
2015-01-30T23:59:59.000Z
Stationary, asymptotically flat spacetimes in general relativity can be characterized by their multipole moments. The moments have proved to be very useful tools for extracting information about the spacetime from various observables and, more recently, for establishing universalities in the structure of neutron stars. As a first step toward extending these methods beyond general relativity, we develop the formalism that allows one to define and calculate the multipole moments in scalar-tensor theories of gravity.
Dangerous implications of a minimum length in quantum gravity
Cosimo Bambi; Katherine Freese
2008-07-17T23:59:59.000Z
The existence of a minimum length and a generalization of the Heisenberg uncertainty principle seem to be two fundamental ingredients required in any consistent theory of quantum gravity. In this letter we show that they would predict dangerous processes which are phenomenologically unacceptable. For example, long--lived virtual super--Planck mass black holes may lead to rapid proton decay. Possible solutions of this puzzle are briefly discussed.
A Vacuum Solution with Torsion in Higher-Derivative Gravity
Kouzou Nishida
2012-09-02T23:59:59.000Z
In this paper, we provide a vacuum solution with torsion in quadratic Riemann-curvature gravity. Physically, the solution means that vacuum can have a nonzero vacuum field with large torsion. We show that the Einstein-Hilbert action can be derived if we expand the quadratic curvature of the Lagrangian in a torsion-free Riemannian space-time around a nonzero vacuum field. We also show that the cosmological constant caused by a nonzero vacuum field is equal to zero.
Comments on Cahill's Quantum Foam Inflow Theory of Gravity
T. D. Martin
2004-07-20T23:59:59.000Z
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.
Higher dimensional gravity invariant under the Poincare group
P. Salgado; M. Cataldo; S. del Campo
2002-05-30T23:59:59.000Z
It is shown that the Stelle-West Grignani-Nardelli-formalism allows, both when odd dimensions and when even dimensions are considered, constructing actions for higher dimensional gravity invariant under local Lorentz rotations and under local Poincar\\`{e} translations. It is also proved that such actions have the same coefficients as those obtained by Troncoso and Zanelli in ref. Class. Quantum Grav. 17 (2000) 4451.
Solar system constraints on f(G) gravity models
Antonio De Felice; Shinji Tsujikawa
2009-07-10T23:59:59.000Z
We discuss solar system constraints on f(G) gravity models, where f is a function of the Gauss-Bonnet term G. We focus on cosmologically viable f(G) models that can be responsible for late-time cosmic acceleration. These models generally give rise to corrections of the form epsilon*(r/rs)^p to the vacuum Schwarzschild solution, where epsilon = H^2 rs^2 solar system constraints for a wide range of model parameters.
Self-Gravity Driven Instabilities in the ISM
R. M. Hueckstaedt; J. H. Hunter Jr; R. V. E. Lovelace
2006-03-29T23:59:59.000Z
In order to understand star formation it is important to understand the dynamics of atomic and molecular clouds in the interstellar medium (ISM). Nonlinear hydrodynamic flows are a key component to the ISM. One route by which nonlinear flows arise is the onset and evolution of interfacial instabilities. Interfacial instabilities act to modify the interface between gas components at different densities and temperatures. Such an interface may be subject to a host of instabilities, including the Rayleigh-Taylor, Kelvin-Helmholtz, and Richtmyer-Meshkov instabilities. Recently, a new density interface instability was identified. This self-gravity interfacial instability (SGI) causes any displacement of the interface to gr ow on roughly a free-fall time scale, even when the perturbation wavelength is much less than the Jeans length. In previous work, we used numerical simulations to confirm the expectations of linear theory and examine the nonlinear evolution of the SGI. We now continue our study by generalizing our initial conditions to allow the acceleration due to self-gravity to be non-zero across the interface. We also consider the behaviour of the SGI for perturbation wavelengths near the Jeans wavelength. We conclude that the action of self-gravity across a density interface may play a significant role in the ISM either by fueling the growth of new instabilities or modifying the evolution of existing instabilities.
Particlelike solutions in modified gravity: the Higgs monopole
Schlogel, Sandrine; Staelens, Francois; Fuzfa, Andre
2014-01-01T23:59:59.000Z
Higgs inflation has received a remarkable attention in the last few years due to its simplicity and predictive power. The key point of this model is the nonminimal coupling to gravity in unitary gauge. As such, this theory is in fact a scalar-tensor modification of gravity that needs to be studied also below the energy scales of inflation. Motivated by this goal, we study in great analytical and numerical detail the static and spherically symmetric solutions of the equations of motion in the presence of standard baryonic matter, called "Higgs monopoles" and presented in \\cite{monopole}. These particlelike solutions may arise naturally in tensor-scalar gravity with mexican hat potential and are the only globally regular asymptotically flat solutions with finite classical energy. In the case when the parameters of the potential are taken to be the ones of the standard model, we find that the deviations from general relativity are extremely small, especially for bodies of astrophysical size and density. This all...
Noncommutative Gravity and Quantum Field Theory on Noncommutative Curved Spacetimes
Alexander Schenkel
2012-10-03T23:59:59.000Z
The focus of this PhD thesis is on applications, new developments and extensions of the noncommutative gravity theory proposed by Julius Wess and his group. In part one we propose an extension of the usual symmetry reduction procedure to noncommutative gravity. We classify in the case of abelian Drinfel'd twists all consistent deformations of spatially flat Friedmann-Robertson-Walker cosmologies and of the Schwarzschild black hole. The deformed symmetry structure allows us to obtain exact solutions of the noncommutative Einstein equations in many of our models. In part two we develop a new formalism for quantum field theory on noncommutative curved spacetimes by combining methods from the algebraic approach to quantum field theory with noncommutative differential geometry. We also study explicit examples of deformed wave operators and find that there can be noncommutative corrections even on the level of free field theories. The convergent deformation of simple toy models is investigated and it is found that these theories have an improved behaviour at short distances, i.e. in the ultraviolet. In part three we study homomorphisms between and connections on noncommutative vector bundles. We prove that all homomorphisms and connections of the deformed theory can be obtained by applying a quantization isomorphism to undeformed homomorphisms and connections. The extension of homomorphisms and connections to tensor products of bimodules is clarified. As a nontrivial application of the new mathematical formalism we extend our studies of exact noncommutative gravity solutions to more general deformations.
Power counting renormalizability of quantum gravity in Lifshitz spacetime
Takayuki Hirayama
2012-10-25T23:59:59.000Z
We analyse the power counting renormalizability of the quantum field theory of Einstein or Einstein-Gauss-Bonnet gravity in D+2 dimensional Lifshitz spacetime. We show the spectral dimension becomes 2+(D/z) at the UV region where z is the critical exponent. Since it is larger than two, the quantum theory of Einstein gravity is not power counting renormalizable. For the pure Einstein-Gauss-Bonnet gravity, where Lifshitz spacetime is allowed only when the parameters are fine tuned, it happens that the graviton modes do not propagate and the quantum field theory is accidentally renormalizable when z>=D. Another method is discretizing the radial coordinate which changes the spectral dimension to 1+(D/z) at the UV region. Since our four dimensional spacetime is continuous, the four dimensional Lorentz symmetry is recovered at the low energy and the power counting renormalizability is still kept for z>=D, if the spacetime near the null singularity in Lifshitz spacetime is modified into AdS spacetime and the discrete radial direction is compactified like a brane world scenario. We also comment on the AdS/CFT correspondence.
Aspects of Neutrino Oscillation in Alternative Gravity Theories
Sumanta Chakraborty
2015-06-08T23:59:59.000Z
Neutrino spin and flavour oscillation in curved spacetime have been studied for the most general static spherically symmetric configuration. Using the symmetry properties we have derived spin oscillation frequency for neutrino moving along a geodesic or in a circular orbit. Starting from the expression of neutrino spin oscillation frequency we have shown that even in this general context, in high energy limit the spin oscillation frequency for neutrino moving along circular orbit vanishes. This finally lends itself to non-zero probability of neutrino helicity flip. While for neutrino flavour oscillation we have derived general results for oscillation phase, which subsequently have been applied to different gravity theories. These include dilaton field coupled to Maxwell field tensor, generalization of Schwarzschild solution by introduction of quadratic curvature terms of all possible form to the Einstein-Hilbert action and finally regular black hole solutions. In all these cases using the solar neutrino oscillation data we can put bounds on the parameters of these gravity theories. While for spin oscillation probability, we have considered two cases, Gauss-Bonnet term added to the Einstein-Hilbert action and the f(R) gravity theory. In both these cases we could impose bounds on the parameters which are consistent with previous considerations. Implications are also discussed.
Unification of Gravity and Electromagnetism I: Mach's Principle and Cosmology
Partha Ghose
2015-02-12T23:59:59.000Z
The phenomenological consequences of unification of Einstein gravity and electromagnetism in an early phase of a Machian universe with a very small and uniform electrical charge density $\\rho_q$ are explored. A form of the Strong Equivalence Principle for unified electrogravity is first formulated, and it immediately leads to (i) the empirical Schuster-Blackett law relating the magnetic moments and angular momenta of neutral astronomical bodies, (ii) an analogous relation between the linear acceleration of neutral massive bodies and associated electric fields, (iii) gravitational lensing in excess of Einstein gravity, and, with the additional assumption of scaling, to (iv) the Wesson relation between the angular momentum and the square of the mass of astronomical bodies. Incorporation of Sciama's version of Mach's principle leads to a new post-Newtonian dynamics (in the weak field limit of gravity alone without electromagnetism) that predicts flat rotation curves of galaxies without the need of dark matter haloes. Finally, it is shown that the unified theory with a broken symmetry predicts a flat expanding universe with a cosmological term intimately related to electrogravity unification, and can explain WMAP data with a single free parameter. WMAP data require $\\rho_q =6.1\\times 10^{-43}$ C/cc which is too small to be detected at
Disformal Theories of Gravity: From the Solar System to Cosmology
Jeremy Sakstein
2014-10-20T23:59:59.000Z
This paper is concerned with theories of gravity that contain a scalar coupled both conformally and disformally to matter through the metric. By systematically deriving the non-relativistic limit, it is shown that no new non-linear screening mechanisms are present beyond the Vainshtein mechanism and chameleon-like screening. If one includes the cosmological expansion of the universe, disformal effects that are usually taken to be absent can be present in the solar system. When the conformal factor is absent, fifth-forces can be screened on all scales when the cosmological field is slowly-rolling. We investigate the cosmology of these models and use local tests of gravity to place new constraints on the disformal coupling and find $\\mathcal{M}>\\mathcal{O}(\\textrm{eV})$, which is not competitive with laboratory tests. Finally, we discuss the future prospects for testing these theories and the implications for other theories of modified gravity. In particular, the Vainshtein radius of solar system objects can be altered from the static prediction when cosmological time-derivatives are non-negligible.
Solar system tests do not rule out 1/R gravity
Qasem Exirifard
2009-12-28T23:59:59.000Z
We argue that Solar system tests do not rule out 1/R gravity at least due to the reason addressed in Phys. Rev. D 74 (2006) 121501 [astro-ph/0610483] (ref. [1]) and subsequent published papers. Ref. [1] has not only modified the Einstein-Hilbert action but also has changed the boundary conditions since they altered the equations of motion. In Einstein-Hilbert action equations are second order, so the fall off of the fields suffices to single out a unique solution. In 1/R gravity the equations are fourth order, so we should impose additional boundary conditions. Perhaps the boundary condition we must impose is that the abrupt change in the second derivative of the metric near the surface of the Sun remains intact by adding `1/R' corrections to the equations of motion. The solution of 1/R gravity with this boundary condition remains consistent with the solar system tests. Ref. [1] assumes that as soon as they perturbatively modified the equations then the Ricci scalar becomes smooth on the surface of the Sun. This assumption is simply wrong because the boundary conditions and equations of motions are two different entities.
Jin He
2010-01-29T23:59:59.000Z
The starting point of quantum mechanics is the relationship between energy and momentum: energy is proportional to the squared momentum! As a result, energy and momentum have not been treated equally. The wave equation required by quantization is a differential equation which accordingly, does not treat time and space equally. As a result, the Planck constant is not canceled out from the two sides of the equation. Dr. He's gravity is the local bending of background space-time which as suggested by Einstein, can be described by a differential form of second order, and treats time and space equally. Therefore, the Planck constant is completely canceled out in the resulting wave equation. In other words, the quantization of gravity simply does not need the Planck constant!
The Specification Process Background and Motivation
Demurjian, Steven A.
Violate Specification Document Minimal Interactions with Customer + 6 #12;+ + Types of Sotware Engineers
INTERPRETATION OF GRAVITY SURVEYS IN GRASS AND BUENA VISTA VALLEYS, NEVADA
Goldstein, N.E.
2011-01-01T23:59:59.000Z
resistivity, and seismic interpretations along selectedboth gra- vity and seismic interpretations at several pointsValley. Gravity and seismic interpretations also give The
Loop quantum gravity, twistors, and some perspectives on the problem of time
Simone Speziale
2014-04-16T23:59:59.000Z
I give a brief introduction to the relation between loop quantum gravity and twistor theory, and comment on some perspectives on the problem of time.
Ground Gravity Survey At Blue Mountain Geothermal Area (U.S....
Blue Mountain Geothermal Area (U.S. Geological Survey, 2012) Exploration Activity Details Location Blue Mountain Geothermal Area Exploration Technique Ground Gravity Survey...
Reduced Gravity Education Flight Opportunity for Students at Minority Serving Institutions
Broader source: Energy.gov [DOE]
NASA is offering undergraduate students from Minority Serving Institutions an opportunity to test experiments in microgravity aboard NASA's reduced gravity aircraft.
Emergent universe in chameleon, f(R) and f(T) gravity theories
Surajit Chattopadhyay; Ujjal Debnath
2011-05-04T23:59:59.000Z
In this work, we consider an emergent universe in generalized gravity theories like the chameleon, f(R) and f(T) gravities. We reconstruct the potential of the chameleon field under the emergent scenario of the universe and observe its increasing nature with the evolution of the universe. We reveal that in the emergent universe scenario, the equation-of-state parameter behaves like quintessence in the case of f(R) gravity and like phantom in the case of f(T) gravity.
Modified Gravitational Theory and the Gravity Probe-B Gyroscope Experiment
J. W. Moffat
2004-05-17T23:59:59.000Z
A possible deviation from the precession of the Gravity Probe-B gyroscope predicted by general relativity is obtained in the nonsymmetric gravity theory. The time delay of radio signals emitted by spacecraft at planetary distances from the Sun, in nonsymmetric gravity theory is the same as in general relativity. A correction to the precession of the gyroscope would provide a possible experimental signature for the Gravity Probe-B gyroscope experiment. The Lense-Thirring frame-dragging effect is predicted to be the same as in GR.
High specific activity silicon-32
Phillips, D.R.; Brzezinski, M.A.
1996-06-11T23:59:59.000Z
A process for preparation of silicon-32 is provided and includes contacting an irradiated potassium chloride target, including spallation products from a prior irradiation, with sufficient water, hydrochloric acid or potassium hydroxide to form a solution, filtering the solution, adjusting pH of the solution from about 5.5 to about 7.5, admixing sufficient molybdate-reagent to the solution to adjust the pH of the solution to about 1.5 and to form a silicon-molybdate complex, contacting the solution including the silicon-molybdate complex with a dextran-based material, washing the dextran-based material to remove residual contaminants such as sodium-22, separating the silicon-molybdate complex from the dextran-based material as another solution, adding sufficient hydrochloric acid and hydrogen peroxide to the solution to prevent reformation of the silicon-molybdate complex and to yield an oxidation state of the molybdate adapted for subsequent separation by an anion exchange material, contacting the solution with an anion exchange material whereby the molybdate is retained by the anion exchange material and the silicon remains in solution, and optionally adding sufficient alkali metal hydroxide to adjust the pH of the solution to about 12 to 13. Additionally, a high specific activity silicon-32 product having a high purity is provided.
High specific activity silicon-32
Phillips, Dennis R. (Los Alamos, NM); Brzezinski, Mark A. (Santa Barbara, CA)
1996-01-01T23:59:59.000Z
A process for preparation of silicon-32 is provided and includes contacting an irradiated potassium chloride target, including spallation products from a prior irradiation, with sufficient water, hydrochloric acid or potassium hydroxide to form a solution, filtering the solution, adjusting pH of the solution to from about 5.5 to about 7.5, admixing sufficient molybdate-reagent to the solution to adjust the pH of the solution to about 1.5 and to form a silicon-molybdate complex, contacting the solution including the silicon-molybdate complex with a dextran-based material, washing the dextran-based material to remove residual contaminants such as sodium-22, separating the silicon-molybdate complex from the dextran-based material as another solution, adding sufficient hydrochloric acid and hydrogen peroxide to the solution to prevent reformation of the silicon-molybdate complex and to yield an oxidization state of the molybdate adapted for subsequent separation by an anion exchange material, contacting the solution with an anion exchange material whereby the molybdate is retained by the anion exchange material and the silicon remains in solution, and optionally adding sufficient alkali metal hydroxide to adjust the pH of the solution to about 12 to 13. Additionally, a high specific activity silicon-32 product having a high purity is provided.
Conditions for stimulated emission in anomalous gravity-superconductors interactions
G. Modanese; T. Junker
2009-08-19T23:59:59.000Z
Several authors have studied the generation of gravitational fields by condensed-matter systems in non-extreme density conditions. General Relativity and lowest-order perturbative Quantum Gravity predict in this case an extremely small emission rate, so these phenomena can become relevant only if some strong quantum effect occurs. Quantum aspects of gravity are still poorly understood. It is believed that they could play a role in systems which exhibit macroscopic quantum coherence, like superconductors and superfluids, leading to an "anomalous" coupling between matter and field. We mention here recent work in this field by Woods, Chiao, Becker, Agop et al., Ummarino, Kiefer and Weber. New results are presented concerning anomalous stimulated gravitational emission in a layered superconductor like YBCO. We model the superconductor as an array of intrinsic Josephson junctions. The superconducting parameters are defined by our preliminary measurements with melt-textured samples. We write explicitly and solve numerically the Josephson equations which give the normal and super components of the total current in the superconductor, and derive from this the total available power P=IV. Then, assuming that the coefficients A and B for spontaneous and stimulated gravitational emission are known, we apply to this case the Frantz-Nodvik equation for a laser amplifier. The equation is suitably modified in order to allow for a "continuous pumping" given by an oscillating transport current. The conclusions are relevant for the evaluation of gravitational emission from superconductors. We find that even if the A and B coefficients are anomalously large (possibly because of the Quantum Gravity effects mentioned above), the conditions for stimulated emission are quite strict and the emission rate strongly limited by the IV value.
Is Cosmic Acceleration Telling Us Something About Gravity?
Trodden, Mark [Syracuse University, Syracuse, New York, United States
2009-09-01T23:59:59.000Z
Among the possible explanations for the observed acceleration of the universe, perhaps the boldest is the idea that new gravitational physics might be the culprit. In this colloquium I will discuss some of the challenges of constructing a sensible phenomenological extension of General Relativity, give examples of some candidate models of modified gravity and survey existing observational constraints on this approach. I will conclude by discussing how we might hope to distinguish between modifications of General Relativity and dark energy as competing hypotheses to explain cosmic acceleration.
Mutated hybrid inflation in f(R,?R)-gravity
Iihoshi, Masao, E-mail: iihoshi@kiso.phys.se.tmu.ac.jp [Department of Physics, Tokyo Metropolitan University, Hachioji, Tokyo 192-0397 (Japan)
2011-02-01T23:59:59.000Z
A new hybrid inflationary scenario in the context of f(R,?R)-gravity is proposed. Demanding the waterfall field to 'support the potential from below' [unlike the original proposal by Stewart in Phys. Lett. B 345, 414 (1995)], we demonstrate that the scalar potential is similar to that of the large-field chaotic inflation model proposed by Linde in Phys. Lett. B 129, 177 (1983). Inflationary observables are used to constrain the parameter space of our model; in the process, an interesting limit on the number of e-folds N is found.
Three-dimensional geologic structures from inversion of gravity anomalies
Hinson, Charles Alvin
1976-01-01T23:59:59.000Z
. Parameters used were: Zo=7 km, R=l gm/cm , fr=0. 09 km-', fz=0. 125 km iterations=6 and final rms difference was 7. 6 10-4 km. . 42 12 Inversion Model 1. Parameters used were p = 0. 1 gm/cms, zo = 5. 4 km, f& = 0. 045 and fz = 0. 095. Contours... are in kilometers relative to sea level 56 13 Inversion Model 2. Parameters used were p = 0. 1 gm/cm zo = 5. 4 km, fq = 0. 001 and fz = 0. 002. Contours are in kilometers relative to sea level 58 14 Gravity difference between the anomaly produced by Inversion...
Emergence of General Relativity from Loop Quantum Gravity: A Summary
Chun-Yen Lin
2011-12-27T23:59:59.000Z
A model is proposed to demonstrate that classical general relativity can emerge from loop quantum gravity, in a relational description of gravitational field in terms of the coordinates given by matter. Local Dirac observables and coherent states are defined to explore physical content of the model. Expectation values of commutators between the observables for the coherent states recover the four-dimensional diffeomorphism algebra and the large-scale dynamics of the gravitational field relative to the matter coordinates. Both results conform with general relativity up to calculable corrections near singularities.
Momentum relaxation from the fluid/gravity correspondence
Mike Blake
2015-09-10T23:59:59.000Z
We provide a hydrodynamical description of a holographic theory with broken translation invariance. We use the fluid/gravity correspondence to systematically obtain both the constitutive relations for the currents and the Ward identity for momentum relaxation in a derivative expansion. Beyond leading order in the strength of momentum relaxation, our results differ from a model previously proposed by Hartnoll et al. As an application of these techniques we consider charge and heat transport in the boundary theory. We derive the low frequency thermoelectric transport coefficients of the holographic theory from the linearised hydrodynamics.
Momentum relaxation from the fluid/gravity correspondence
Blake, Mike
2015-01-01T23:59:59.000Z
We provide a hydrodynamical description of a holographic theory with broken translation invariance. We use the fluid/gravity correspondence to systematically obtain both the constitutive relations for the currents and the Ward identity for momentum relaxation in a derivative expansion. Beyond leading order in the strength of momentum relaxation, our results differ from a model previously proposed by Hartnoll et al. As an application of these techniques we consider charge and heat transport in the boundary theory. We derive the low frequency thermoelectric transport coefficients of the holographic theory from the linearised hydrodynamics.
Self-gravity in neutrino-dominated accretion disks
Liu, Tong; Yu, Xiao-Fei; Gu, Wei-Min; Lu, Ju-Fu, E-mail: tongliu@xmu.edu.cn [Department of Astronomy and Institute of Theoretical Physics and Astrophysics, Xiamen University, Xiamen, Fujian 361005 (China)
2014-08-10T23:59:59.000Z
We present the effects of self-gravity on the vertical structure and neutrino luminosity of the neutrino-dominated accretion disks in cylindrical coordinates. It is found that significant changes of the structure appear in the outer region of the disk, especially for high accretion rates (e.g., ? 1 M{sub ?} s{sup 1}), and thus cause the slight increase in the neutrino luminosity. Furthermore, the gravitational instability of the disk is reviewed by the vertical distribution of the Toomre parameter, which may account for the late-time flares in gamma-ray bursts and the extended emission in short-duration gamma-ray bursts.
Strong Binary Pulsar Constraints on Lorentz Violation in Gravity
Kent Yagi; Diego Blas; Nicolas Yunes; Enrico Barausse
2014-04-30T23:59:59.000Z
Binary pulsars are excellent laboratories to test the building blocks of Einstein's theory of General Relativity. One of these is Lorentz symmetry which states that physical phenomena appear the same for all inertially moving observers. We study the effect of violations of Lorentz symmetry in the orbital evolution of binary pulsars and find that it induces a much more rapid decay of the binary's orbital period due to the emission of dipolar radiation. The absence of such behavior in recent observations allows us to place the most stringent constraints on Lorentz violation in gravity, thus verifying one of the cornerstones of Einstein's theory much more accurately than any previous gravitational observation.
More on the dilatonic Einstein-Gauss-Bonnet gravity
Masao Iihoshi
2010-11-16T23:59:59.000Z
Einstein-Gauss-Bonnet gravity coupled to a dynamical dilaton is examined from the viewpoint of Einstein's equivalence principle. We point out that the usual frame change that applies to the action without curvature correction does not cure the problem of nonminimal couplings by the dynamical nature of a dilaton field. Thus a modification of the Einstein frame is required. It is proposed that the kinetic term of a dilaton should be brought to a canonical form, which completely fixes the additional terms associated with the frame transformation.
Discrete canonical analysis of three dimensional gravity with cosmological constant
J. Berra-Montiel; J. E. Rosales-Quintero
2014-06-03T23:59:59.000Z
We discuss the interplay between standard canonical analysis and canonical discretization in three-dimensional gravity with cosmological constant. By using the Hamiltonian analysis, we find that the continuum local symmetries of the theory are given by the on-shell space-time diffeomorphisms, which at the action level, corresponds to the Kalb-Ramond transformations. At the time of discretization, although this symmetry is explicitly broken, we prove that the theory still preserves certain gauge freedom generated by a constant curvature relation in terms of holonomies and the Gauss's law in the lattice approach.
More on the dilatonic Einstein-Gauss-Bonnet gravity
Iihoshi, Masao
2010-01-01T23:59:59.000Z
Einstein-Gauss-Bonnet gravity coupled to a dynamical dilaton is examined from the viewpoint of Einstein's equivalence principle. We point out that the usual frame change that applies to the action without curvature correction does not cure the problem of nonminimal couplings by the dynamical nature of a dilaton field. Thus a modification of the Einstein frame is required. It is proposed that the kinetic term of a dilaton should be brought to a canonical form, which completely fixes the additional terms associated with the frame transformation.
Noncommutative Theories, Seiberg-Witten Map, and Gravity
Rivelles, Victor O. [Instituto de Fisica, Universidade de Sao Paulo, Caixa Postal 66318, 05315-970, Sao Paulo, SP (Brazil)
2005-04-04T23:59:59.000Z
In this paper we review the connection between noncommutative field theories and gravity. When the noncommutativity is induced by the Moyal product we can use the Seiberg-Witten map in order to deal with ordinary fields. We then show that the effect of the noncommutativity is the same as a field dependent gravitational background. The gravitational background is that of a gravitational plane wave and the coupling is charge dependent. Uncharged fields couple more strongly than the charged ones. Deviations from the usual dispersion relations are discussed and we show that they are also charge dependent.
Computing model independent perturbations in dark energy and modified gravity
Battye, Richard A. [Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL (United Kingdom); Pearson, Jonathan A., E-mail: richard.battye@manchester.ac.uk, E-mail: jonathan.pearson@durham.ac.uk [Department of Mathematical Sciences, Durham University, South Road, Durham, DH1 3LE (United Kingdom)
2014-03-01T23:59:59.000Z
We present a methodology for computing model independent perturbations in dark energy and modified gravity. This is done from the Lagrangian for perturbations, by showing how field content, symmetries, and physical principles are often sufficient ingredients for closing the set of perturbed fluid equations. The fluid equations close once ''equations of state for perturbations'' are identified: these are linear combinations of fluid and metric perturbations which construct gauge invariant entropy and anisotropic stress perturbations for broad classes of theories. Our main results are the proof of the equation of state for perturbations presented in a previous paper, and the development of the required calculational tools.
Translation invariant time-dependent massive gravity: Hamiltonian analysis
Jihad Mourad; Karim Noui; Danièle A. Steer
2014-07-10T23:59:59.000Z
The canonical structure of the massive gravity in the first order moving frame formalism is studied. We work in the simplified context of translation invariant fields, with mass terms given by general non-derivative interactions, invariant under the diagonal Lorentz group, depending on the moving frame as well as a fixed reference frame. We prove that the only mass terms which give 5 propagating degrees of freedom are the dRGT mass terms, namely those which are linear in the lapse. We also complete the Hamiltonian analysis with the dynamical evolution of the system.
Black Holes in 2+1 Teleparallel Theories of Gravity
A. A. Sousa; J. W. Maluf
2003-01-21T23:59:59.000Z
We apply the Hamiltonian formulation of teleparallel theories of gravity in 2+1 dimensions to a circularly symmetric geometry. We find a family of one-parameter black hole solutions. The BTZ solution fixes the unique free parameter of the theory. The resulting field equations coincide with the teleparallel equivalent of Einstein's three-dimensional equations. We calculate the gravitational energy of the black holes by means of the simple expression that arises in the Hamiltonian formulation and conclude that the resulting value is identical to that calculated by means of the Brown-York method.
Ground Gravity Survey At Marysville Mt Area (Blackwell) | Open Energy
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on DeliciousPlasmaP aCentrothermDepew, NewAl., 2012) |GreenBrillianceGreenwood,GriggsOpenInformation Ground Gravity
Ground Gravity Survey At Valles Caldera - Sulphur Springs Geothermal Area
AFDC Printable Version Share this resource Send a link to EERE: Alternative Fuels Data Center Home Page to someone by E-mail Share EERE: Alternative Fuels Data Center Home Page on Facebook Tweet about EERE: Alternative Fuels Data Center Home Page on Twitter Bookmark EERE: Alternative Fuels Data Center Home Page on Google Bookmark EERE: Alternative Fuels Data Center Home Page on DeliciousPlasmaP aCentrothermDepew, NewAl., 2012)Information Ground Gravity Survey At Snake River Plain(Wilt &
Anomalous diffusion for inertial particles under gravity in parallel flows
Marco Martins Afonso
2014-07-04T23:59:59.000Z
We investigate the bounds between normal or anomalous effective diffusion for inertial particles transported by parallel flows. The infrared behavior of the fluid kinetic-energy spectrum, i.e. the possible presence of long-range spatio-temporal correlations, is modeled as a power law by means of two parameters, and the problem is studied as a function of these latter. Our results, obtained in the limit of weak relative inertia, extend well-known results for tracers and apply to particles of any mass density, subject to gravity and Brownian diffusion. We consider both steady and time-dependent flows, and cases of both vanishing and finite particle sedimentation.
Lessons from Classical Gravity about the Quantum Structure of Spacetime
Padmanabhan, T
2010-01-01T23:59:59.000Z
I present the theoretical evidence which suggests that gravity is an emergent phenomenon like gas dynamics or elasticity with the gravitational field equations having the same status as, say, the equations of fluid dynamics/elasticity. This paradigm views a wide class of gravitational theories - including Einstein's theory - as describing the thermodynamic limit of the statistical mechanics of "atoms of spacetime". The evidence for this paradigm is hidden in several classical features of the gravitational theories and depends on just one quantum mechanical input, viz. the existence of Davies-Unruh temperature of horizons. I discuss several conceptual ingredients of this approach.
Lessons from Classical Gravity about the Quantum Structure of Spacetime
T. Padmanabhan
2011-01-22T23:59:59.000Z
I present the theoretical evidence which suggests that gravity is an emergent phenomenon like gas dynamics or elasticity with the gravitational field equations having the same status as, say, the equations of fluid dynamics/elasticity. This paradigm views a wide class of gravitational theories - including Einstein's theory - as describing the thermodynamic limit of the statistical mechanics of "atoms of spacetime". The evidence for this paradigm is hidden in several classical features of the gravitational theories and depends on just one quantum mechanical input, viz. the existence of Davies-Unruh temperature of horizons. I discuss several conceptual ingredients of this approach.
On precanonical quantization of gravity in spin connection variables
Kanatchikov, I. V. [National Center of Quantum Information in Gdansk (KCIK), 81-824 Sopot (Poland)
2013-02-21T23:59:59.000Z
The basics of precanonical quantization and its relation to the functional Schroedinger picture in QFT are briefly outlined. The approach is then applied to quantization of Einstein's gravity in vielbein and spin connection variables and leads to a quantum dynamics described by the covariant Schroedinger equation for the transition amplitudes on the bundle of spin connection coefficients over space-time, that yields a novel quantum description of space-time geometry. A toy model of precanonical quantum cosmology based on the example of flat FLRW universe is considered.
Critical points of D-dimensional extended gravities
Deser, S.; Liu Haishan; Lue, H.; Pope, C. N.; Sisman, Tahsin Cagri; Tekin, Bayram [Physics Department, Brandeis University, Waltham, Massachusetts 02454 (United States) and Lauritsen Laboratory, California Institute of Technology, Pasadena, California 91125 (United States); Zheijiang Institute of Modern Physics, Department of Physics, Zheijiang University, Hangzhou 310027 (China); China Economics and Management Academy, Central University of Finance and Economics, Beijing 100081 and Institute for Advanced Study, Shenzhen University, Nanhai Ave 3688, Shenzhen 518060 (China); George P. and Cynthia Woods Mitchell Institute for Fundamental Physics and Astronomy, Texas A and M University, College Station, Texas 77843 (United States) and DAMTP, Centre for Mathematical Sciences, Cambridge University, Wilberforce Road, Cambridge CB3 OWA (United Kingdom); Department of Physics, Middle East Technical University, 06531, Ankara (Turkey)
2011-03-15T23:59:59.000Z
We study the parameter space of D-dimensional cosmological Einstein gravity together with quadratic curvature terms. In D>4 there are in general two distinct (anti)-de Sitter vacua. We show that, for an appropriate choice of the parameters, there exists a critical point for one of the vacua, with only massless tensor, but neither massive tensor nor scalar, gravitons. At criticality, the linearized excitations have formally vanishing energy (as do black hole solutions). A further restriction of the parameters gives a one-parameter cosmological Einstein plus Weyl{sup 2} model with a unique vacuum, whose {Lambda} is determined.
Inflationary universe from higher-derivative quantum gravity
Ratbay Myrzakulov; Sergei Odintsov; Lorenzo Sebastiani
2015-04-08T23:59:59.000Z
We consider higher-derivative quantum gravity where renormalization group improved effective action beyond one-loop approximation is derived. Using this effective action, the quantum-corrected FRW equations are analyzed. De Sitter universe solution is found. It is demonstrated that such de Sitter inflationary universe is instable. The slow-roll inflationary parameters are calculated. The contribution of renormalization group improved Gauss-Bonnet term to quantum-corrected FRW equations as well as to instability of de Sitter universe is estimated. It is demonstrated that in this case the spectral index and tensor-to-scalar ratio are consistent with Planck data.
Inflationary universe from higher-derivative quantum gravity
Myrzakulov, Ratbay; Sebastiani, Lorenzo
2014-01-01T23:59:59.000Z
We consider higher-derivative quantum gravity where renormalization group improved effective action beyond one-loop approximation is derived. Using this effective action, the quantum-corrected FRW equations are analyzed. De Sitter universe solution is found. It is demonstrated that such de Sitter inflationary universe is instable. The slow-roll inflationary parameters are calculated. The contribution of renormalization group improved Gauss-Bonnet term to quantum-corrected FRW equations as well as to instability of de Sitter universe is estimated. It is demonstrated that in this case the spectral index and tensor-to-scalar ratio are consistent with Planck data.
Model Commissioning Plan and Guide Specifications
NONE
1997-03-01T23:59:59.000Z
The objectives of Model Commissioning Plan and Guide Specifications are to ensure that the design team applies commissioning concepts to the design and prepares commissioning specifications and a commission plan for inclusion in the bid construction documents.
Multivariate Statistical Analysis of Assembly Tolerance Specifications
i Multivariate Statistical Analysis of Assembly Tolerance Specifications A Thesis Presented ..........................................................................................................12 2.6.1 Multivariate Normal Distributions.8.3 Combined Assembly Specification Quality...............................................22 2.9 Multivariate
Runtime verification of object lifetime specifications
Benjamin, Zev (Zev A.)
2009-01-01T23:59:59.000Z
This thesis reports on the implementation of a runtime verification system for object lifetime specifications. This system is used to explore and evaluate the expressiveness object lifetime specifications. Object lifetime ...
Unit Testing for Casl Architectural Specifications
Sannella, Don
and impractical activity. When only finite sets of interactions are considered, successful testing can accept Unit Testing for Casl Architectural Specifications. The problem of testing modular systems against algebraic specifications is discussed. We focus on systems
Graceful Degradation Via Versions: Specifications and Implementations
Thekkath, Chandramohan A.
Graceful Degradation Via Versions: Specifications and Implementations Lidong Zhou, Vijayan to degraded system behavior that deviates from the system's specification and even causing complete unavailability of the system. This paper advocates the notion of graceful degradation as a complementary
Cuesta, C M
2011-01-01T23:59:59.000Z
We derive a boundary layer equation describing accumulation regions within a thin-film approximation framework where gravity and surface tension balance. As part of the analysis of this problem we investigate in detail and rigorously the 'drainage' equation (phi"'+1)phi^3=1. In particular, we prove that all solutions that do not tend to 1 as the independent variable goes to infinity are oscillatory, and that they oscillate in a very specific way. This result and the method of proof will be used in the analysis of solutions of the afore mentioned boundary layer problem.
Peter Arnold; Diana Vaman
2010-10-25T23:59:59.000Z
Previous studies of high-energy jet stopping in strongly-coupled plasmas have lacked a clear gauge-theory specification of the initial state. We show how to set up a well-defined gauge theory problem to study jet stopping in pure {\\cal N}=4 super Yang Mills theory (somewhat analogous to Hofman and Maldacena's studies at zero temperature) and solve it by using gauge-gravity duality for real-time, finite-temperature 3-point correlators. Previous studies have found that the stopping distance scales with energy as E^{1/3} (with disagreement on the gauge coupling dependence). We do find that none of the jet survives beyond this scale, but we find that almost all of our jet stops at a parametrically smaller scale proportional to (E L)^{1/4}, where L is the size of the space-time region where the jet is initially created.
Barthelemy, X; Peirson, W L; Fedele, F; Allis, M; Dias, F
2015-01-01T23:59:59.000Z
We revisit the classical, but as yet unresolved problem of predicting the breaking onset of 2D and 3D irrotational gravity water waves. This study focuses on domains with flat bottom topography and conditions ranging from deep to intermediate depth (depth to wavelength ratio between 1 and 0.2). Using a fully-nonlinear boundary element model, our initial calculations investigated geometric, kinematic and energetic differences between maximally recurrent and marginally breaking waves in focusing wave groups. Maximallyrecurrent waves are clearly separated from marginally-breaking waves by their energy fluxes localized near the crest region. Specifically, tracking the local ratio of energy flux velocity to crest speed at the crest of the tallest wave in the evolving group provides a robust breaking onset threshold parameter. Warning of imminent breaking onset was found to depend on the strength of breaking, but was detectable only up to half a carrier wave period prior to a breaking event.
and Yaoguo Li, Center for Gravity, Electrical and Magnetic Studies, Department of Geophysics, Colorado School of geophysical data has been widely uti- lized in data interpretation in both hydrocarbon and mineral exploration
Alternative approach to the regularization of odd dimensional AdS gravity
Pablo Mora
2007-08-23T23:59:59.000Z
In this paper I present an action principle for odd dimensional AdS gravity which consists of introducing another manifold with the same boundary and a very specific boundary term. This new action allows and alternative approach to the regularization of the theory, yielding a finite euclidean action and finite conserved charges. The choice of the boundary term is justified on the grounds that an enhanced 'almost off-shell' local AdS/Conformal symmetry arises for that very special choice. One may say that the boundary term is dictated by a guiding symmetry principle. Two sets of boundary conditions are considered, which yield regularization procedures analogous to (but different from) the standard 'background substraction' and 'counterterms' regularization methods. The Noether charges are constructed in general. As an application it is shown that for Schwarszchild-AdS black holes the charge associated to the time-like Killing vector is finite and is indeed the mass. The Euclidean action for Schwarzschild-AdS black holes is computed, and it turns out to be finite, and to yield the right thermodynamics. The previous paragraph may be interpreted in the sense that the boundary term dictated by the symmetry principle is the one that correctly regularizes the action.
Methods for chromosome-specific staining
Gray, Joe W. (Livermore, CA); Pinkel, Daniel (Walnut Creek, CA)
1995-01-01T23:59:59.000Z
Methods and compositions for chromosome-specific staining are provided. Compositions comprise heterogenous mixtures of labeled nucleic acid fragments having substantially complementary base sequences to unique sequence regions of the chromosomal DNA for which their associated staining reagent is specific. Methods include methods for making the chromosome-specific staining compositions of the invention, and methods for applying the staining compositions to chromosomes.
Enhanced Specific Heat of Silica Donghyun Shin
Banerjee, Debjyoti
Enhanced Specific Heat of Silica Nanofluid Donghyun Shin Debjyoti Banerjee e-mail: dbanerjee instrument was used to measure the specific heat of the neat molten salt eutectic and after addition of nanoparticles. The specific heat of the nanofluid was enhanced by 1924%. The mea- surement uncertainty
HEART RATE AND BLOOD PRESSURE VARIABILITY UNDER MOON, MARS AND ZERO GRAVITY CONDITIONS DURING), studied via the heart rate variability (HRV) and blood pressure variability (BPV). HRV and BPV were predominant during reduced gravity. For the mean heart rate, a non-monotonic relation was found, which can
Enhanced Oil Recovery through Steam Assisted Gravity Drainage January 22, 2014
Cirpka, Olaf Arie
Enhanced Oil Recovery through Steam Assisted Gravity Drainage January 22, 2014 A Comparative Study Of Continuous And Cyclic Steam Injection With Trapping Of Oil Phase Muhammad Adil Javed Summary of Thesis Enhanced oil recovery (EOR) through steam-assisted gravity drainage (SAGD) has become an important in
French Guidelines for Structural Safety of Gravity Dams in a Semi-probabilistic Format
Paris-Sud XI, Université de
French Guidelines for Structural Safety of Gravity Dams in a Semi-probabilistic Format Paul Royet1 the French Committee on Dams and Reservoirs FrCOLD - issued provisional guidelines for structural safety of gravity dams. It was the first attempt to produce a semi-probabilistic limit-state method for the design
Large-Scale Flow Response to the Breaking of Mountain Gravity Waves
Lott, Francois
Large-Scale Flow Response to the Breaking of Mountain Gravity Waves François Lott, LMD, Ecole and synoptic impacts of mountain gravity waves breaking observations Some diagnostics tools Parameterization in weather prediction and climate models 3) Interaction between a front and an idealised mountain massive
Gravity anomalies, crustal structure and thermo-mechanical support of the Himalaya of Central Nepal
Avouac, Jean-Philippe
Gravity anomalies, crustal structure and thermo-mechanical support of the Himalaya of Central Nepal, Department of Mines and Geology, Lainchaur, Kathmandu, Nepal Accepted 2001 June 8. Received 2001 January 6; in original form 2000 February 4 SUMMARY We use two gravity profiles that we measured across Central Nepal
Augmented gravity model: An empirical application to Mercosur-European Union trade flows
Krivobokova, Tatyana
DB Nr. 77 Augmented gravity model: An empirical application to Mercosur-European Union trade flows Inmaculada Martínez-Zarzoso Felicitas Nowak-Lehmann D. Abstract This paper applies the gravity trade model to assess Mercosur-European Union trade, and trade potential following the agreements reached recently
A stress interpretation scheme applied to lunar gravity and topography data
A stress interpretation scheme applied to lunar gravity and topography data F. Chambat1 and B. In the crust, because of topography, the strongest stress differences take place on the far side, with large), A stress interpretation scheme applied to lunar gravity and topography data, J. Geophys. Res., 113, E02009
Mesoscale simulations of gravity waves during the 20082009 major stratospheric sudden warming
Limpasuvan, Varavut
Mesoscale simulations of gravity waves during the 20082009 major stratospheric sudden warming September 2011. [1] A series of 24 h mesoscale simulations (of 10 km horizontal and 400 m vertical. Yamashita (2011), Mesoscale simulations of gravity waves during the 20082009 major stratospheric sudden
Energy deposition of 24 GeV/c protons in gravity affected
McDonald, Kirk
Energy deposition of 24 GeV/c protons in gravity affected mercury jet Sergei Striganov Fermilab Data Analysis(latest update : 07Oct08), including dispersion term. Â· If there is vacuum only between +- 15 degree 75 +- 15 degree #12;Energy deposition density in round gravity affected jet at 5 Tesla, r=8
Online Center of Gravity Estimation in Automotive Vehicles using Multiple Models and Switching
Duffy, Ken
Online Center of Gravity Estimation in Automotive Vehicles using Multiple Models and Switching and switching for realtime estimation of center of gravity (CG) position in automotive vehicles. The method utilizes simple linear vehicle models and assumes availability of standard stock automotive sensors. We
Time in quantum gravity Nick Huggett, Tiziana Vistarini, and Christian Wuthrich
Wüthrich, Christian
Time in quantum gravity Nick Huggett, Tiziana Vistarini, and Christian W¨uthrich For Adrian Bardon and Heather Dyke (eds.), The Blackwell Companion to the Philosophy of Time. Abstract Quantum gravity for the nature of physical time. Some of these lessons shall be canvassed here, particularly as they arise from
PHYSICS OF FLUIDS 25, 086604 (2013) Gravity currents shoaling on a slope
Sutherland, Bruce
2013-01-01T23:59:59.000Z
-release laboratory experiments.713 In these, a gate inserted in a long rectangular tank separates fluid of one den water rivers into the saline ocean form surface gravity currents. The study of gravity currents is also motivated by industrial processes including the sudden release of dense gases in the atmosphere and oil
Ozgökmen, Tamay M.
Entrainment in bottom gravity currents over complex topography from three km to 1 m, the impact of topographic bumps on entrainment in gravity currents is investigated using enhancement of entrainment compared to a smooth surface. The change in entrainment is parameterized
Parameterization of gravity current entrainment for ocean circulation models using a high-order 3D
Ozgökmen, Tamay M.
Parameterization of gravity current entrainment for ocean circulation models using a high-order 3D on the work by Turner [Turner, J.S., 1986. The development of the entrainment assumption and its application. Weather Rev. 128, 14021419], an algebraic parameterization of the entrainment process in gravity current
Constraining the density of CO2 within the Utsira formation using time-lapse gravity measurements
Nooner, Scott
best fit a high temperature forward model based on the seismically determined CO2 geometry, suggesting to study the behavior and physical properties of the injected CO2. The gravity measurements show1 Constraining the density of CO2 within the Utsira formation using time-lapse gravity measurements
Big Bang Nucleosynthesis Constraints on the Self-Gravity of Pressure
Saul Rappaport; Josiah Schwab; Scott Burles; Gary Steigman
2007-10-28T23:59:59.000Z
Using big bang nucleosynthesis and present, high-precision measurements of light element abundances, we constrain the self-gravity of radiation pressure in the early universe. The self-gravity of pressure is strictly non-Newtonian, and thus the constraints we set provide a direct test of this prediction of general relativity and of the standard, Robertson-Walker-Friedmann cosmology.
Constraints on the Self-Gravity of Radiation Pressure via Big Bang Nucleosynthesis
Saul Rappaport; Josiah Schwab; Scott Burles
2007-07-24T23:59:59.000Z
Using standard big-bang nucleosynthesis and present, high-precision measurements of light element abundances, we place constraints on the self-gravity of radiation pressure in the early universe. The self-gravity of pressure is strictly non-Newtonian, and thus the constraints we set are a direct test of this aspect of general relativity.
Wald's gravitational entropy for ghost-free, infinite derivative theories of Gravity
Conroy, Aindriú; Teimouri, Ali
2015-01-01T23:59:59.000Z
In this paper, we demonstrate that the Wald's entropy for any spherically symmetric blackhole within an infinite derivative theory of gravity is determined solely by the area law. Thus, the infrared behaviour of gravity is captured by the Einstein-Hilbert term, provided that the massless graviton remains the only propagating degree of freedom in the spacetime.
Power-law cosmic expansion in f(R) gravity models
Naureen Goheer; Julien Larena; Peter K. S. Dunsby
2009-06-21T23:59:59.000Z
We show that within the class of f(R) gravity theories, FLRW power-law perfect fluid solutions only exist for R^n gravity. This significantly restricts the set of exact cosmological solutions which have similar properties to what is found in standard General Relativity.
Ionospheric gravity waves detected offshore Hawaii after tsunamis Lucie M. Rolland,1
Occhipinti, Giovanni "Ninto"
that these gravity waves might be detectable and used for tsunami warning system purpose. [3] Taking advantageIonospheric gravity waves detected offshore Hawaii after tsunamis Lucie M. Rolland,1 Giovanni an important role in the continuous oce- anic survey to prevent the damage produced by powerful tsunamis. We
Enhanced Turbulence due to the Superposition of Internal Gravity Waves and a Coastal Upwelling Jet
Enhanced Turbulence due to the Superposition of Internal Gravity Waves and a Coastal Upwelling Jet to shear instability. Yet, enhanced turbulence is observed in the upwelling jet, typically as long, thin), the latter during upwelling conditions (summer). Linear internal gravity waves (IGW) also have significant
Enhanced turbulence due to the superposition of internal gravity waves and a coastal upwelling jet
Enhanced turbulence due to the superposition of internal gravity waves and a coastal upwelling jet instability. Yet enhanced turbulence is observed in the upwelling jet, typically as long, thin patches), Enhanced turbulence due to the superposition of internal gravity waves and a coastal upwelling jet, J
A numerical study on the effects of pressure and gravity in laminar ethylene diffusion flames
Gülder, Ömer L.
A numerical study on the effects of pressure and gravity in laminar ethylene diffusion flames Marc 26 March 2011 Keywords: High-pressure Zero-gravity Laminar ethylene diffusion flames Soot modeling were studied numeri- cally in coflow ethyleneair laminar diffusion flames between 0.5 and 5 atm
A numerical study on the effects of pressure and gravity in laminar ethylene diffusion flames
Groth, Clinton P. T.
A numerical study on the effects of pressure and gravity in laminar ethylene diffusion flames Marc xxxx Keywords: High-pressure Zero-gravity Laminar ethylene diffusion flames Soot modeling a b s t r a c in coflow ethyleneair laminar diffusion flames between 0.5 and 5 atm. Computations were per- formed
Time-lapse gravity monitoring of an aquifer storage recovery project in Leyden, Colorado Kristofer on using time-lapse micro-gravity surveying to monitor an aquifer storage recovery project. An abandoned coal mine is being developed into an underground water reservoir in Leyden, Colorado. Excess water from
GRAVITY WAVE DYNAMICS AND EFFECTS IN THE MIDDLE David C. Fritts and M. Joan Alexander
Alexander, M. Joan
GRAVITY WAVE DYNAMICS AND EFFECTS IN THE MIDDLE ATMOSPHERE David C. Fritts and M. Joan Alexander gravity waves have been a subject of intense research activity in recent years because of their myriad occasionally strong lower-atmospheric effects, the major wave influences occur in the middle atmosphere, be
Nazarenko, Sergey
Gravity Wave Turbulence in Wave Tanks: Space and Time Statistics Sergei Lukaschuk,1,* Sergey the first simultaneous space-time measurements for gravity wave turbulence in a large laboratory flume. We found that the slopes of k and ! wave spectra depend on wave intensity. This cannot be explained by any
The Spin-Statistics Connection in Quantum Gravity
A. P. Balachandran; E. Batista; I. P. Costa e Silva; P. Teotonio-Sobrinho
1999-06-23T23:59:59.000Z
It is well-known that is spite of sharing some properties with conventional particles, topological geons in general violate the spin-statistics theorem. On the other hand, it is generally believed that in quantum gravity theories allowing for topology change, using pair creation and annihilation of geons, one should be able to recover this theorem. In this paper, we take an alternative route, and use an algebraic formalism developed in previous work. We give a description of topological geons where an algebra of "observables" is identified and quantized. Different irreducible representations of this algebra correspond to different kinds of geons, and are labeled by a non-abelian "charge" and "magnetic flux". We then find that the usual spin-statistics theorem is indeed violated, but a new spin-statistics relation arises, when we assume that the fluxes are superselected. This assumption can be proved if all observables are local, as is generally the case in physical theories. Finally, we also show how our approach fits into conventional formulations of quantum gravity.
Gauge/String-Gravity Duality and Froissart Bound
Kyungsik Kang
2004-10-16T23:59:59.000Z
The gauge/string-gravity duality correspondence opened renewed hope and possibility to address some of the fundamental and non-perturbative QCD problems in particle physics, such as hadron spectrum and Regge behavior of the scattering amplitude at high energies. One of the most fundamental and long-standing problem is the high energy behavior of total cross-sections. According to a series of exhaustive tests by the COMPETE group, (1). total cross-sections have a universal Heisenberg behavior in energy corresponding to the maximal energy behavior allowed by the Froissart bound, i.e., $A + B ln^2 (s/s_0)$ with $B \\sim 0.32 mb$ and $s_0 \\sim 34.41 GeV^2$ for all reactions, and (2). the factorization relation among $\\sigma_{pp, even}, \\sigma_{\\gamma p}, and \\sigma_{\\gamma \\gamma}$ is well satisfied by experiments. I discuss the recent interesting application of the gauge/string-gravity duality of $AdS/CFT$ correspondence with a deformed background metric so as to break the conformal symmetry that can lead to the Heisenberg behavior of rising total cross-sections, and present some preliminary results on the high energy QCD from Planckian scattering in $AdS$ and black-hole production.
New second derivative theories of gravity for spherically symmetric spacetimes
Rakesh Tibrewala
2015-03-17T23:59:59.000Z
We present new second derivative, generally covariant theories of gravity for spherically symmetric spacetimes (general covariance is in the $t-r$ plane) belonging to the class where the spherically symmetric Einstein-Hilbert theory is modified by the presence of $g_{\\theta\\theta}$ dependent functions. In $3+1$ dimensional vacuum spacetimes there is three-fold infinity of freedom in constructing such theories as revealed by the presence of three arbitrary $g_{\\theta\\theta}$ dependent functions in the Hamiltonian (matter Hamiltonian also has the corresponding freedom). This result is not a contradiction to the theorem of Hojman et. al. [1] which is applicable to the full theory whereas the above conclusion is for symmetry reduced sector of the theory (which has a much reduced phase space). In the full theory where there are no special symmetries, the result of Hojman et. al. will continue to hold. In the process we also show that theories where the constraint algebra is deformed by the presence of $g_{\\theta\\theta}$ dependent functions - as is the case in the presence of inverse triad corrections in loop quantum gravity - can always be brought to the form where they obey the standard (undeformed) constraint algebra by performing a suitable canonical transformation. We prove that theories obtained after performing canonical transformation are inequivalent to the symmetry reduced general relativity and that the resulting theories fall within the purview of the theories mentioned above.
Conformal symmetries of gravity from asymptotic methods: further developments
Pierre-Henry Lambert
2014-09-16T23:59:59.000Z
In this thesis, the symmetry structure of gravitational theories at null infinity is studied further, in the case of pure gravity in four dimensions and also in the case of Einstein-Yang-Mills theory in $d$ dimensions with and without a cosmological constant. The first part of this thesis is devoted to the presentation of asymptotic methods (symmetries, solution space and surface charges) applied to gravity in the case of the BMS gauge in three and four spacetime dimensions. The second part of this thesis contains the original contributions. Firstly, it is shown that the enhancement from Lorentz to Virasoro algebra also occurs for asymptotically flat spacetimes defined in the sense of Newman-Unti. As a first application, the transformation laws of the Newman-Penrose coefficients characterizing solution space of the Newman-Unti approach are worked out, focusing on the inhomogeneous terms that contain the information about central extensions of the theory. These transformations laws make the conformal structure particularly transparent, and constitute the main original result of the thesis. Secondly, asymptotic symmetries of the Einstein-Yang-Mills system with or without cosmological constant are explicitly worked out in a unified manner in $d$ dimensions. In agreement with a recent conjecture, a Virasoro-Kac-Moody type algebra is found not only in three dimensions but also in the four dimensional asymptotically flat case. These two parts of the thesis are supplemented by appendices.
Modified Gravity N-body Code Comparison Project
Hans A. Winther; Fabian Schmidt; Alexandre Barreira; Christian Arnold; Sownak Bose; Claudio Llinares; Marco Baldi; Bridget Falck; Wojciech A. Hellwing; Kazuya Koyama; Baojiu Li; David F. Mota; Ewald Puchwein; Robert Smith; Gong-Bo Zhao
2015-06-21T23:59:59.000Z
Self-consistent ${\\it N}$-body simulations of modified gravity models are a key ingredient to obtain rigorous constraints on deviations from General Relativity using large-scale structure observations. This paper provides the first detailed comparison of the results of different ${\\it N}$-body codes for the $f(R)$, DGP, and Symmetron models, starting from the same initial conditions. We find that the fractional deviation of the matter power spectrum from $\\Lambda$CDM agrees to better than $1\\%$ up to $k \\sim 5-10~h/{\\rm Mpc}$ between the different codes. These codes are thus able to meet the stringent accuracy requirements of upcoming observational surveys. All codes are also in good agreement in their results for the velocity divergence power spectrum, halo abundances and halo profiles. We also test the quasi-static limit, which is employed in most modified gravity ${\\it N}$-body codes, for the Symmetron model for which the most significant non-static effects among the models considered are expected. We conclude that this limit is a very good approximation for all of the observables considered here.
Perturbations of Single-field Inflation in Modified Gravity Theory
Taotao Qiu; Jun-Qing Xia
2015-04-12T23:59:59.000Z
In this paper, we study the case of single field inflation within the framework of modified gravity theory where the gravity part has an arbitrary form $f(R)$. Via a conformal transformation, this case can be transformed into its Einstein frame where it looks like a two-field inflation model. However, due to the existence of the isocurvature modes in such a multi-degree-of-freedom (m.d.o.f.) system, the (curvature) perturbations are not equivalent in two frames, so in despite of its convenience, it is illegal to treat the perturbations in its Einstein frame as the "real" ones as we always do for pure $f(R)$ theory or single field with nonminimal coupling. Here by pulling the results of curvature perturbations back into its original Jordan frame, we show explicitly the power spectrum and spectral index of the perturbations in the Jordan frame, as well as how it differs from the Einstein frame. We also fit our results with the newest Planck data. Since there are large parameter space in these models, we show that it is easy to fit the data very well.
Perturbations of Single-field Inflation in Modified Gravity Theory
Qiu, Taotao
2015-01-01T23:59:59.000Z
In this paper, we study the case of single field inflation within the framework of modified gravity theory where the gravity part has an arbitrary form $f(R)$. Via a conformal transformation, this case can be transformed into its Einstein frame where it looks like a two-field inflation model. However, due to the existence of the isocurvature modes in such a multi-degree-of-freedom (m.d.o.f.) system, the perturbations are not equivalent in two frames, so in despite of its convenience, it is illegal to treat the perturbations in its Einstein frame as the "real" ones as we always do for pure $f(R)$ theory or single field with nonminiaml coupling, and one should pull them back into its original Jordan frame. In this paper, we calculate the perturbations in such a case in its Jordan frame. We also fit our results with the newest Planck data. Since there are large parameter space in these models, we show that it is easy to fit the data very well.