Revisiting the temperature evolution law of the CMB with gaussian processes
arXiv:2505.24543 · doi:10.1016/j.physletb.2025.139606
Abstract
In this work, we perform a statistical inference of the classical background law governing the evolution of the temperature of the cosmic microwave background radiation (CMB), given by . To this end, we employ Gaussian Process (GP) regression techniques to reconstruct the temperature evolution based on two observational datasets: (i) CMB-Sunyaev-Zel'dovich (SZ) cluster measurements and (ii) CMB-interstellar medium (ISM) interaction data. Our analysis reveals interesting results that may suggest potential deviations from the standard temperature-redshift relation, particularly at low redshifts (), where discrepancies up to 2 are observed. Additionally, we identify a mild but noteworthy tension, also at the 2 level, between our GP inferred value of the present-day CMB temperature, , and the precise direct measurement from the COBE/FIRAS experiment. We also explore possible phenomenological implications of our findings, including interpretations associated with possible variations in fundamental constants, such as the fine-structure constant , which could provide a physical explanation for the observed deviations at low redshift.
8 pages, 6 figures
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