Redshift dependence of CMB temperature in BSBM α-varying theories
We have investigated some cosmological consequences of variation of the fine structure constant, α, in the context of the Bekenstein-Sandvik-Barrow-Magueijo (BSBM) model. In this context, such a variation is attributed to the electric charge by letting the latter take on the value of a real scalar field, ϕ, which varies generally in space and time. We consider the dynamics of ϕ in the case that it is allowed to have an exponential potential. We have found solutions for evolutions of ϕ and α in the radiation and the matter dominated eras. By employing observational bounds on the temporal variation of α, we constrain the model parameters. We then investigate the impact of α-variation on the redshift dependence of the CMB temperature. It is shown that there is a deviation from the standard evolution of the temperature which contains two different contributions, one is important at high-redshift eras and the other is mostly effective at low-redshift eras.