Current and future cosmological impact of microwave background temperature measurements

TL;DR

This paper evaluates how measurements of the cosmic microwave background temperature at various redshifts can constrain cosmological models, especially those explaining universe acceleration, and discusses future improvements with advanced facilities.

Contribution

It extends previous analyses by including models with torsion and varying speed of light, showing these measurements' comparable constraining power to other cosmological probes.

Findings

Current measurements constrain models with torsion and varying speed of light.

Next-generation facilities can significantly improve these constraints.

CMB temperature measurements often provide orthogonal parameter constraints.

Abstract

The redshift dependence of the cosmic microwave background temperature, $T(z)=T_0(1+z)$, is a key prediction of standard cosmology, but this relation is violated in many extensions thereof. Current astrophysical facilities can probe it in the redshift range $0\le z\le6.34$. We extend recent work by Gelo {\it et al.} (2022) showing that for several classes of models (all of which aim to provide alternative mechanisms for the recent acceleration of the universe) the constraining power of these measurements is comparable to that of other background cosmology probes. Specifically, we discuss constraints on two classes of models not considered in the earlier work: a model with torsion and a recently proposed phenomenological dynamical dark energy model which can be thought of as a varying speed of light model. Moreover, for both these models and also for those in the earlier work, we discuss how current constraints may be improved by next-generation ground and space astrophysical facilities. Overall, we conclude that these measurements have a significant cosmological impact, mainly because they often constrain combinations of model parameters that are orthogonal, in the relevant parameter space, to those of other probes.