Cosmic Acceleration in LRS Bianchi Type-I & II Cosmological Models with Variable EoS Parameter

Abstract

The  present study deals  with spatially homogeneous and  locally  rotationally symmetric (LRS)  Bianchi type-I  and  Bianchi  type-II  cosmological  models  representing  cosmological  constant  Λ as  the dark  energy candidate.  The  physical  and  geometrical behavior of  cosmological  solutions to the Einstein’s field equations with suitable physical  assumptions, have  been  investigated in scalar-tensor theory of gravitation proposed by  Saez  and  Ballester (Phys.  Lett.  A 113:  467,  1986)  and  a new  parametrization for EoS parameter ω(z) has been obtained.  Further, it is concluded that variation of EoS parameter ω from positive to negative values justifies transition of the universe  from decelerating phase to present accelerating phase  and  ω → −1 points towards the presence  of dark  energy  candidate Λ in present universe.