Regular Article - Theoretical Physics

Thermodynamic implications of the gravitationally induced particle creation scenario

¹ Department of Physical Sciences, Indian Institute of Science Education and Research Kolkata, Mohanpur, 741246, West Bengal, India
² Department of Astrophysics and Cosmology, S N Bose National Centre for Basic Sciences, Block-JD, Sector-III, Saltlake, Kolkata, 700106, West Bengal, India

^* e-mail: subhajit1729@gmail.com

Received: 20 December 2016
Accepted: 7 March 2017
Published online: 27 March 2017

Abstract

A rigorous thermodynamic analysis has been done as regards the apparent horizon of a spatially flat Friedmann–Lemaitre–Robertson–Walker universe for the gravitationally induced particle creation scenario with constant specific entropy and an arbitrary particle creation rate . Assuming a perfect fluid equation of state with , the first law, the generalized second law (GSL), and thermodynamic equilibrium have been studied, and an expression for the total entropy (i.e., horizon entropy plus fluid entropy) has been obtained which does not contain explicitly. Moreover, a lower bound for the fluid temperature has also been found which is given by . It has been shown that the GSL is satisfied for . Further, when is constant, thermodynamic equilibrium is always possible for , while for and , equilibrium can never be attained. Thermodynamic arguments also lead us to believe that during the radiation phase, . When is not a constant, thermodynamic equilibrium holds if , however, such a condition is by no means necessary for the attainment of equilibrium.