Existence and Non existence of String Cosmological Models in Bimetric Theory of Gravitation

Abstract

In this paper, I have investigated   some magnetized cosmological modes with and without magnetic field  in Rosen’s bimetric theory of gravitation .To get determinate solution we have assumed that σ is proportional to θ and ζθ = constant where σ is shear, θ is the expansion in the model and  is the coefficient of bulk viscosity.  The model exists for , for positive . The model never dusty with zero value of   and model describes dusty universe   for   with   In the   absence of magnetic field  the  model exist for     and the model is dusty  for  and in this case the  cosmological constant  always  positive.

The bulk viscosity  makes a role and affects the physical behavior of the model. In the absence of it, the model does not exist, since    and  all are negative. Further in the absence of both magnetic field  and bulk viscosity  , the model represents vacuum   universe with zero cosmological constant  but has a constant shear.