arXiv Analytics

Sign in

arXiv:astro-ph/0604485AbstractReferencesReviewsResources

On the Growth of Perturbations as a Test of Dark Energy

Edmund Bertschinger

Published 2006-04-23, updated 2006-05-13Version 3

The strongest evidence for dark energy comes presently from geometric techniques such as the supernova distance-redshift relation. By combining the measured expansion history with the Friedmann equation one determines the energy density and its time evolution, hence the equation of state of dark energy. Because these methods rely on the Friedmann equation which has not been independently tested it is desirable to find alternative methods that work for both general relativity and other theories of gravity. Assuming that sufficiently large patches of a perturbed Robertson-Walker spacetime evolve like separate Robertson-Walker universes, that shear stress is unimportant on large scales and that energy and momentum are locally conserved, we derive several relations between long-wavelength metric and matter perturbations. These relations include generalizations of the initial-value constraints of general relativity. For a class of theories including general relativity we reduce the long-wavelength metric, density, and velocity potential perturbations to quadratures including curvature perturbations, entropy perturbations, and the effects of nonzero background curvature. When combined with the expansion history measured geometrically, the long-wavelength solution provide a test that may distinguish modified gravity from other explanations of dark energy.

Comments: 25 pages, 1 figure, submitted to ApJ; references added; expanded discussion of entropy perturbations, initial-value constraints and alternative theories of gravity
Journal: Astrophys.J.648:797-806,2006
Categories: astro-ph, gr-qc
Related articles: Most relevant | Search more
arXiv:astro-ph/0309756 (Published 2003-09-28, updated 2004-12-08)
Cosmology calculations almost without general relativity
arXiv:astro-ph/0311250 (Published 2003-11-11)
The traditional approximation in general relativity
arXiv:astro-ph/0703416 (Published 2007-03-15, updated 2007-11-30)
The Weak Energy Condition and the Expansion History of the Universe