Bulk viscous string cosmological models in Saez-Ballester theory of gravity
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ORIGINAL ARTICLE
Bulk viscous string cosmological models in Saez-Ballester theory of gravity R.K. Mishra1 · Heena Dua1
Received: 13 September 2019 / Accepted: 4 November 2019 © Springer Nature B.V. 2019
Abstract In this communication, a new class of bulk viscous string cosmological models has been constructed in Saez-Ballester theory of gravitation. To obtain the deterministic solution of the field equations, we have considered deceleration parameter as a bilinear function of cosmic time t for model I and special parametrization of Hubble parameter for model II. The presented class of the cosmological models indicate phase conversion from early decelerated expansion phase to present accelerated expansion phase. To discuss the dynamicity of the universe, the behaviour of various physical parameters has also been studied and presented graphically. For stability analysis, the nature of various energy conditions is investigated. Statefinder pair analysis is used to discriminate the constructed models with other dark energy models and it is noticed that the proposed models are in good agreement with recent observational data. Keywords Saez-Ballester theory · Deceleration parameter · Cosmological models · Dark energy
1 Introduction The study of cosmological model is based on the general theory of relativity (GTR) which is one of the important theories of modern theoretical physics. It has the ability to explain the real physical phenomenon. In most branches of
B R.K. Mishra
[email protected] H. Dua [email protected]
1
Department of Mathematics, Sant Longowal Institute of Engineering and Technology, Deemed University, Under MHRD, Govt. of India, Longowal 148 106, Punjab, India
physics, various experiments have been performed and theories have to be fit into the observations. We are also familiar with the fact that in case of any comparison between theory and observation, we have to establish certain framework in which we may apply the theory. Such frameworks have been constructed by many authors under different circumstances. After formulating GTR and testing it on the grounds of solar experiments, Einstein had used this theory for the construction of models of the universe. He also proposed that universe is static like a static sphere filled with matter (Einstein 1917). According to GTR, construction of static cosmological models is possible by adding the term gμν into Einstein field equations, here is a cosmological constant. Later on, Einstein realised that universe is not static and called this “the biggest mistake of his life” (Gamow 1970). Thereafter, many non-static cosmological models were developed by various scientists who laid down the foundation for such study (De Sitter 1917; Lemaître 1927). It is evident from literature that from the date of the formation of GTR to till date, certain shortcomings of the theory have been observed by many scientists. One of the such is deviation from Mach’s principle which was pointed out by Einstein himself. Also, the standard big bang model of the univer
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