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Abstract:

We study the background cosmology governed by the Tensor-Vector-Scalar theory of gravity proposed by Bekenstein. We consider a broad family of potentials that lead to modified gravity and calculate the evolution of the field variables both numerically and analytically. We find a range of possible behaviors, from scaling to the late time domination of either the additional gravitational degrees of freedom or the background fluid.

Abstract:

A range of experimental results point to the existence of a massive neutrino. The recent high precision measurements of the cosmic microwave background and the large scale surveys of galaxies can be used to place an upper bound on this mass. In this paper we perform a thorough analysis of all assumptions that go into obtaining a credible limit on $\sum m_{\nu}$. In particular we explore the impact of extending parameter space beyond the current standard cosmological model, the importance of priors and the uncertainties due to biasing in large scale structure. We find that the mass constraints are independent of the choice of parameterization as well as the inclusion of spatial curvature. The results of including the possibility of dark energy and tensors perturbations are shown to depend critically on the data sets used. The difference between an upper bound of 2.2 eV, assuming generic initial conditions, and an upper bound of 0.63 eV, assuming adiabaticity and a galaxy bias of 1, demonstrate the dependence of such a constraint on the assumptions in the analysis.