Probing cosmic acceleration beyond the equation of state: Distinguishing between dark energy and modified gravity models

Mustapha Ishak, Amol Upadhye, and David N. Spergel
Phys. Rev. D 74, 043513 – Published 15 August 2006

Abstract

If general relativity is the correct theory of physics on large scales, then there is a differential equation that relates the Hubble expansion function, inferred from measurements of angular diameter distance and luminosity distance, to the growth rate of large scale structure. For a dark energy fluid without couplings or an unusual sound speed, deviations from this consistency relationship could be the signature of modified gravity on cosmological scales. We propose a procedure based on this consistency relation in order to distinguish between some dark energy models and modified gravity models. The procedure uses different combinations of cosmological observations and is able to find inconsistencies when present. As an example, we apply the procedure to a universe described by a recently proposed 5-dimensional modified gravity model. We show that this leads to an inconsistency within the dark energy parameter space detectable by future experiments.

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  • Received 15 July 2005

DOI:https://doi.org/10.1103/PhysRevD.74.043513

©2006 American Physical Society

Authors & Affiliations

Mustapha Ishak1,2,*, Amol Upadhye3, and David N. Spergel2

  • 1Department of Physics, The University of Texas at Dallas, Richardson, Texas 75083, USA
  • 2Department of Astrophysical Sciences, Princeton University, Princeton, New Jersey 08544, USA
  • 3Department of Physics, Princeton University, Princeton, New Jersey 08544, USA

  • *Electronic Address: mishak@utdallas.edu; Electronic address: mishak@princeton.edu

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Vol. 74, Iss. 4 — 15 August 2006

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