Searching for cosmological signatures of the Einstein equivalence principle breaking

Understand

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 $\eta$.