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Title: Separating dark physics from physical darkness: Minimalist modified gravity versus dark energy

Abstract

The acceleration of the cosmic expansion may be due to a new component of physical energy density or a modification of physics itself. Mapping the expansion of cosmic scales and the growth of large scale structure in tandem can provide insights to distinguish between the two origins. Using Minimal Modified Gravity (MMG) - a single parameter gravitational growth index formalism to parametrize modified gravity theories - we examine the constraints that cosmological data can place on the nature of the new physics. For next generation measurements combining weak lensing, supernovae distances, and the cosmic microwave background we can extend the reach of physics to allow for fitting gravity simultaneously with the expansion equation of state, diluting the equation of state estimation by less than 25% relative to when general relativity is assumed, and determining the growth index to 8%. For weak lensing we examine the level of understanding needed of quasi- and nonlinear structure formation in modified gravity theories, and the trade off between stronger precision but greater susceptibility to bias as progressively more nonlinear information is used.

Authors:
 [1];  [2]
  1. Kavli Institute for Cosmological Physics and Astronomy and Astrophysics Department, University of Chicago, Chicago, Illinois 60637 (United States)
  2. Berkeley Lab, University of California, Berkeley, California 94720 (United States)
Publication Date:
OSTI Identifier:
20935218
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physical Review. D, Particles Fields; Journal Volume: 75; Journal Issue: 2; Other Information: DOI: 10.1103/PhysRevD.75.023519; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS; ACCELERATION; COSMOLOGICAL MODELS; ENERGY DENSITY; EQUATIONS OF STATE; EXPANSION; GENERAL RELATIVITY THEORY; GRAVITATION; MAPPING; NONLINEAR PROBLEMS; NONLUMINOUS MATTER; RELICT RADIATION

Citation Formats

Huterer, Dragan, and Linder, Eric V. Separating dark physics from physical darkness: Minimalist modified gravity versus dark energy. United States: N. p., 2007. Web. doi:10.1103/PHYSREVD.75.023519.
Huterer, Dragan, & Linder, Eric V. Separating dark physics from physical darkness: Minimalist modified gravity versus dark energy. United States. doi:10.1103/PHYSREVD.75.023519.
Huterer, Dragan, and Linder, Eric V. Mon . "Separating dark physics from physical darkness: Minimalist modified gravity versus dark energy". United States. doi:10.1103/PHYSREVD.75.023519.
@article{osti_20935218,
title = {Separating dark physics from physical darkness: Minimalist modified gravity versus dark energy},
author = {Huterer, Dragan and Linder, Eric V.},
abstractNote = {The acceleration of the cosmic expansion may be due to a new component of physical energy density or a modification of physics itself. Mapping the expansion of cosmic scales and the growth of large scale structure in tandem can provide insights to distinguish between the two origins. Using Minimal Modified Gravity (MMG) - a single parameter gravitational growth index formalism to parametrize modified gravity theories - we examine the constraints that cosmological data can place on the nature of the new physics. For next generation measurements combining weak lensing, supernovae distances, and the cosmic microwave background we can extend the reach of physics to allow for fitting gravity simultaneously with the expansion equation of state, diluting the equation of state estimation by less than 25% relative to when general relativity is assumed, and determining the growth index to 8%. For weak lensing we examine the level of understanding needed of quasi- and nonlinear structure formation in modified gravity theories, and the trade off between stronger precision but greater susceptibility to bias as progressively more nonlinear information is used.},
doi = {10.1103/PHYSREVD.75.023519},
journal = {Physical Review. D, Particles Fields},
number = 2,
volume = 75,
place = {United States},
year = {Mon Jan 15 00:00:00 EST 2007},
month = {Mon Jan 15 00:00:00 EST 2007}
}
  • The acceleration of the cosmic expansion may be due to a new component of physical energy density or a modification of physics itself. Mapping the expansion of cosmic scales and the growth of large scale structure in tandem can provide insights to distinguish between the two origins. Using Minimal Modified Gravity (MMG) - a single parameter gravitational growth index formalism to parameterize modified gravity theories - we examine the constraints that cosmological data can place on the nature of the new physics. For next generation measurements combining weak lensing, supernovae distances, and the cosmic microwave background we can extend themore » reach of physics to allow for fitting gravity simultaneously with the expansion equation of state, diluting the equation of state estimation by less than 25percent relative to when general relativity is assumed, and determining the growth index to 8percent. For weak lensing we examine the level of understanding needed of quasi- and nonlinear structure formation in modified gravity theories, and the trade off between stronger precision but greater susceptibility to bias as progressively more nonlinear information is used.« less
  • We develop the general scheme for modified f(R) gravity reconstruction from any realistic Friedmann-Robertson-Walker (FRW) cosmology. We formulate several versions of modified gravity compatible with solar system tests where the following sequence of cosmological epochs occurs: (a) matter dominated phase (with or without usual matter), transition from deceleration to acceleration, accelerating epoch consistent with recent WMAP data, (b) {lambda}CDM cosmology without cosmological constant. As a rule, such modified gravities are expressed implicitly (in terms of special functions) with late-time asymptotics of known type (for instance, the model with negative and positive powers of curvature). In the alternative approach, it ismore » demonstrated that even simple versions of modified gravity may lead to the unification of matter dominated and accelerated phases at the price of the introduction of compensating dark energy.« less
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  • The bulk motion of galaxies induced by the growth of cosmic structure offers a rare opportunity to test the validity of general relativity across cosmological scales. However, modified gravity can be degenerate in its effect with the unknown values of cosmological parameters. More seriously, even the 'observed' value of the redshift-space distortions used to measure the fluctuation growth rate depends on the assumed cosmological parameters (the Alcock-Paczynski effect). We give a full analysis of these issues, showing how to combine redshift-space distortions with baryon acoustic oscillations and CMB data, in order to obtain joint constraints on deviations from general relativitymore » and on the equation of state of dark energy while allowing for factors such as nonzero curvature. In particular we note that the evolution of {Omega}{sub m}(z), along with the Alcock-Paczynski effect, produces a degeneracy between the equation of state w and the modified growth parameter {gamma}. Typically, the total marginalized error on either of these parameters will be larger by a factor {approx_equal}2 compared to the conditional error where one or the other is held fixed. We argue that future missions should be judged by their figure of merit as defined in the w{sub p}-{gamma} plane, and note that the inclusion of spatial curvature can degrade this value by an order of magnitude.« less
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