2015/06/30 by Louis Perenon, Louis Pèrenon, Federico Piazza +2 · 1 citation
Physics and Astronomy · #Cosmological perturbation theory #Cosmology and Gravitation Theories #Dark energy #Dark matter #Galaxies: Formation, Evolution, Phenomena #Gravitation #Parameter space #Perturbation (astronomy) #Phenomenology (philosophy) #Redshift #Scalar field #Solar and Space Plasma Dynamics #astro-ph.CO #gr-qc #hep-ph #hep-th
paper · pdf · doi:10.1088/1475-7516/2015/11/029
published as JCAP 1511 (2015) no.11, 029 · 24 pages, 7 figures
arxiv created 2015/07/10 · openalex publication_date 2015/11/16 · openalex created_date 2016/06/24 · arxiv updated 2019/06/03 · openalex updated_date 2026/08/05
We present a systematic exploration of dark energy and modified gravity models containing a single scalar field non-minimally coupled to the metric. Even though the parameter space is large, by exploiting an effective field theory (EFT) formulation and by imposing simple physical constraints such as stability conditions and (sub-)luminal propagation of perturbations, we arrive at a number of generic predictions. (1) The linear growth rate of matter density fluctuations is generally suppressed compared to ΛCDM at intermediate redshifts (0.5 ≲ z ≲ 1), despite the introduction of an attractive long-range scalar force. This is due to the fact that, in self-accelerating models, the background gravitational coupling weakens at intermediate redshifts, over-compensating the effect of the attractive scalar force. (2) At higher redshifts, the opposite happens; we identify a period of super-growth when the linear growth rate is larger than that predicted by ΛCDM. (3) The gravitational slip parameter η—the ratio of the space part of the metric perturbation to the time part—is bounded from above. For Brans-Dicke-type theories η is at most unity. For more general theories, η can exceed unity at intermediate redshifts, but not more than about 1.5 if, at the same time, the linear growth rate is to be compatible with current observational constraints. We caution against phenomenological parametrization of data that do not correspond to predictions from viable physical theories. We advocate the EFT approach as a way to constrain new physics from future large-scale-structure data.