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

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.

Effective gravitational couplings for cosmological perturbations in the most general scalar–tensor theories with second-order field equations

“…Our analysis in this paper covers those theories as specific cases. Such general analysis will be useful to discriminate between modified gravitational models from the observations of large-scale structure, weak lensing, and CMB [39]. This paper is organized as follows.…”

SKA weak lensing – III. Added value of multiwavelength synergies for the mitigation of systematics

“…Weak lensing is particularly valuable because it probes both the background evolution of the Universe and the growth of cosmic structures. For this reason, it has been advocated as an optimal way to test dark matter (Bacon & Taylor 2003;Taylor et al 2004;Camera et al , 2015Shirasaki et al 2014), dark energy (Amendola et al 2008;Taylor et al 2007;Heavens et al 2006;Beynon et al 2012;Camera & Nishizawa 2013) and modified gravity (Ishak et al 2006;Heavens et al 2007;Tsujikawa & Tatekawa 2008;Schmidt 2008; ⋆ E-mail: stefano.camera@manchester.ac.uk 2010; Belloso et al 2011;Camera et al 2009Camera et al , 2011a, in particular in combination with galaxy number counts and other observables (Hu & Jain 2004;Jain & Zhang 2008;Camera et al 2012Camera et al , 2014.…”

Weak lensing, dark matter and dark energy

“…More generally, measuring γ can distinguish between modified gravity and dark energy even if the two predict identical expansion history (e.g. distances in the universe; for a similar approach not using the growth index, see [110,111]). Future expectations are for γ to be measured to accuracy of about 0.02-0.03 from weak lensing data combined with other cosmological probes that measure the distance scale (SNe Ia, CMB) or growth (cluster abundance) [103,112]; see Fig.…”