Proposal for the origin of the cosmological constant

Abstract

We work in the framework of a simple vector-tensor theory. The parametrized post-Newtonian approximation of this theory is identical to that of general relativity. Our attention is focused on cosmology. In an homogeneous isotropic universe, it is proved that the energy density, ${\rho }_A$, of the vector field $A$, and its pressure, $p_A$, do not depend on time, and also that the equation of state is ${\rho }_A=-p_A$. This means that, in the theory under consideration, there is a cosmological constant, which is not vacuum energy, but the dark energy of the cosmic vector field $A$, whose evolution is classical.

12 pages, 1 figure. See addendum