Cosmological Solutions of Tensora€“Vector Theories of Gravity by Varying the Space-Timea€“Matter Coupling Constant

摘要

We consider tensora€“vector theories by varying the space-timea€“matter coupling constant (varying Einstein velocity) in a spatially flat FRW universe.We examine the dynamics of this model by dynamical system method assuming a e???CDM background and we find some exact solutions by considering the character of critical points of the theory and their stability conditions. Then we reconstruct the potential e?‘‰(e??′2) and the coupling e?‘?(e??′2) by demanding a background e???CDM cosmology. Also we set restrictions on the varying Einstein velocity to solve the horizon problem. This gives a selection rule for choosing the appropriate stable solution. We will see that it is possible to produce the background expansion history e???(e?‘§) indicated by observations. Finally we will discuss the behavior of the speed of light (e?‘?E) for those solutions.