Searching for cosmological signatures of the Einstein equivalence principle breaking

TL;DR

This paper investigates potential cosmological signatures of Einstein equivalence principle breaking by analyzing galaxy cluster data and supernovae, finding no evidence for such deviations.

Contribution

It introduces a method to test Einstein equivalence principle breaking using combined galaxy cluster and supernova data, accounting for their dependence on fundamental constants.

Findings

No evidence of Einstein equivalence principle breaking found.

Constraints on deviations of fundamental constants established.

Method accounts for the dependence of observational techniques on fundamental constants.

Abstract

Modifications of gravity generated by a multiplicative coupling of a scalar field to the electromagnetic Lagrangian lead to a breaking of Einstein equivalence principle (EEPB) as well as to variations of fundamental constants. In these theoretical frameworks, deviations of standard values of the fine structure constant, $\Delta \alpha/\alpha=\phi$, and of the cosmic distance duality relation, $D_L(1+z)^{-2}/D_A=\eta=1$, where $D_L$ and $D_A$ are the luminosity and angular diameter distances, respectively, are unequivocally linked. In this paper, we search for cosmological signatures of the EEPB by using angular diameter distance from galaxy clusters, obtained via their Sunyaev-Zeldovich effect (SZE) and X-ray observations, and distance modulus of type Ia supernovae (SNe Ia). The crucial point here is that we take into account the dependence of the SZE/X-ray technique with $\phi$ and $\eta$. Our new results show no indication of the EEPB.