1303.1773 (Carsten van de Bruck et al.)

Constraints on Disformal Couplings from the CMB Temperature Evolution    [PDF]

Carsten van de Bruck, Jack Morrice, Susan Vu

Certain modified gravity theories predict the existence of an additional, non-conformally coupled scalar field. A disformal coupling of the field to the Cosmic Microwave Background (CMB) is shown to affect the evolution of the energy density in the radiation fluid. Therefore, measurements of the CMB temperature at various redshifts can be used to constrain these disformal couplings. Such measurements strongly support the predictions of General Relativity, that the CMB temperature evolution with redshift is linear. For both exponential and power law potentials for the scalar field we find an excluded range for the strength of this coupling, characterised by an energy scale $M$, to be few$\times 10^{-5}$ eV$View original: http://arxiv.org/abs/1303.1773