This paper discusses about Robertson-Walker space-time with quadratic equation of state and dynamical cosmological parameter Λ. Some exact solutions of Einstein’s field equations for three cases have been obtained. Physical behaviors of the models are discussed in detail. | Communications in Physics, Vol. 25, No. 4 (2015), pp. 309-316 DOI: ISOTROPIC ROBERTSON-WALKER MODEL UNIVERSE WITH DYNAMICAL COSMOLOGICAL PARAMETER Λ IN BRANS-DICKE THEORY OF GRAVITATION KANGUJAM PRIYOKUMAR SINGH AND MUKUNDA DEWRI Department of Mathematical Sciences, Bodoland University, Kokrajhar, PIN-783370, BTC, Assam, India Received 19 October 2015 Accepted for publication 09 December 2015 E-mail: dewri11@ Abstract. This paper discusses about Robertson-Walker space-time with quadratic equation of state and dynamical cosmological parameter Λ. Some exact solutions of Einstein’s field equations for three cases have been obtained. Physical behaviors of the models are discussed in detail. Keywords: Brans-Dicke theory, dark energy, quadratic equation of state. I. INTRODUCTION The Brans-Dicke (B-D) theory [1] of gravitation is one of the simplest and best understood scalar-tensor theories. As a result B-D theory has attained significant attention in recent years. Cosmological models in Brans-Dicke theory is discussed by many authors [2–10]. The cosmological and astronomical data obtained from the Supernovae Ia(SNeIa), the cosmic microwave background (CMB) radiation anisotropies, the Large Scale Structure (LSS) and X-ray experiments support the discovery of accelerated expansion of the present day universe [11–19]. The accelerated expansion of universe is due to the presence of dark energy which has positive energy density and adequate negative pressure [20, 21]. Chen and Wu [22] considered Λ varying as R−2 , Carvalho and Lima [23] generalized it. Beesham [24], Tiwari [25], Harpreet and Tiwari [26], Kotambkar et al. [27] are some of the authors who studied cosmological model with variable G and Λ. Nojiri and Odintsov [28], Capozziello [29], Chavanis [30], Sharma and Rantnapal [31], Takisa et al. [32], Feroze and Siddiqui [33] are some of the authors who have discussed about cosmological models with equation of state in quadratic .
