Temperature-redshift relation in energy-momentum-powered gravity models

TL;DR

Energy-momentum-powered gravity models modify Einstein's equations and can explain cosmic acceleration without a cosmological constant, but they conflict with the observed temperature-redshift relation, leading to tight constraints on model parameters.

Contribution

This paper demonstrates that energy-momentum-powered gravity models violate the temperature-redshift relation and provides new, tighter observational constraints on their parameters using astrophysical and cosmological data.

Findings

Models are constrained to |n|<0.01 or |n|<0.1, improving previous limits.

Violation of temperature-redshift relation rules out certain parameter ranges.

Constraints on matter density are also tightened.

Abstract

There has been recent interest in the cosmological consequences of energy-momentum-powered gravity models, in which the matter side of Einstein's equations includes a term proportional to some power, $n$, of the energy-momentum tensor, in addition to the canonical linear term. Previous works have suggested that these models can lead to a recent accelerating universe without a cosmological constant, but they can also be seen as phenomenological extensions of the standard $\Lambda$CDM, which are observationally constrained to be close to the $\Lambda$CDM limit. Here we show that these models violate the temperature-redshift relation, and are therefore further constrained by astrophysical measurements of the cosmic microwave background temperature. We provide joint constraints on these models from the combination of astrophysical and background cosmological data, showing that this power is constrained to be about $|n|<0.01$ and $|n|<0.1$, respectively in models without and with a cosmological constant, and improving previous constraints on this parameter by more than a factor of three. By breaking degeneracies between this parameter and the matter density, constraints on the latter are also improved by a factor of about two.