Phase Transition in Cosmology with Magnetic Field.

In this paper we have investigated the Bianchi type-II cosmological model with variable parameters in the frame work of modified f(R,T) gravity theory as suggested by Harko et al. (Phys. Rev. D, 84:024020). As we know that the effect of space-time curvature upon phase transition is an expanding universe. In this communication we have constructed a cosmological model of the universe by taking suitable assumptions along with string in presence of magnetic field. It is to be noted that our procedure for solving the field equations is different from other authors as we have consider the time dependent deceleration parameter (DP), it means that the universe which was decelerating in the past is accelerating at present time. We found that the universe is decelerating for q>0 and accelerating for-1q≤q<0, which shown signature flipping. [ABSTRACT FROM AUTHOR]