Sub-percent constraints on cosmological temperature evolution

TL;DR

This paper combines current measurements of the cosmic microwave background temperature to tightly constrain deviations from the standard temperature-redshift relation, achieving the first sub-percent limit on the deviation parameter.

Contribution

It provides the first sub-percent constraint on the temperature evolution deviation parameter using combined direct and indirect measurements.

Findings

The deviation parameter β is constrained to (7.6 ± 8.0)×10⁻³ at 68.3% confidence.

Current data strongly supports the standard temperature-redshift relation.

The analysis sets a new benchmark for testing cosmological models.

Abstract

The redshift dependence of the cosmic microwave background temperature is one of the key cosmological observables. In the standard cosmological model one has $T(z)=T_0(1+z)$, where $T_0$ is the present-day temperature. Deviations from this behavior would imply the presence of new physics. Here we discuss how the combination of all currently available direct and indirect measurements of $T(z)$ constrains the common phenomenological parametrization $T(z)=T_0(1+z)^{1-\beta}$, and obtain the first sub-percent constraint on the $\beta$ parameter, specifically $\beta=(7.6\pm8.0)\times10^{-3}$ at the $68.3\%$ confidence level.