Low redshift constraints on energymomentumpowered gravity models
Abstract
There has been recent interest in the cosmological consequences of energymomentumpowered gravity models, in which the matter side of Einstein's equations is modified by the addition of a term proportional to some power, n, of the energymomentum tensor, in addition to the canonical linear term. In this work we treat these models as phenomenological extensions of the standard ΛCDM, containing both matter and a cosmological constant. We also quantitatively constrain the additional model parameters using low redshift background cosmology data that are specifically from Type Ia supernovas and Hubble parameter measurements. We start by studying specific cases of these models with fixed values of n, which lead to an analytic expression for the Friedmann equation; we discuss both their current constraints and how the models may be further constrained by future observations of Type Ia supernovas for WFIRST complemented by measurements of the redshift drift by the ELT. We then consider and constrain a more extended parameter space, allowing n to be a free parameter and considering scenarios with and without a cosmological constant. These models do not solve the cosmological constant problem per se. Nonetheless these models can phenomenologically lead to a recent accelerating universe without a cosmological constant at the cost of having a preferred matter density of around Ω_{M} ∼ 0.4 instead of the usual Ω_{M} ∼ 0.3. Finally we also briefly constrain scenarios without a cosmological constant, where the single component has a constant equation of state which needs not be that of matter; we provide an illustrative comparison of this model with a more standard dynamical dark energy model with a constant equation of state.
 Publication:

Astronomy and Astrophysics
 Pub Date:
 May 2019
 DOI:
 10.1051/00046361/201935551
 arXiv:
 arXiv:1905.02792
 Bibcode:
 2019A&A...625A.127F
 Keywords:

 cosmology: theory;
 dark energy;
 cosmology: observations;
 cosmological parameters;
 methods: statistical;
 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Phenomenology;
 High Energy Physics  Theory
 EPrint:
 13+2 pages, 12+1 figures