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Advances in High Energy Physics
Volume 2017 (2017), Article ID 7650238, 24 pages
https://doi.org/10.1155/2017/7650238
Research Article

Irreversible Thermodynamic Description of Dark Matter and Radiation Creation during Inflationary Reheating

1School of Physics, Sun Yat-Sen University, Guangzhou 510275, China
2Yat Sen School, Sun Yat-Sen University, Guangzhou 510275, China
3Department of Physics, Babes-Bolyai University, Kogalniceanu Street, 400084 Cluj-Napoca, Romania
4Department of Mathematics, University College London, Gower Street, London WC1E 6BT, UK
5State Key Laboratory of Optoelectronic Material and Technology and Guangdong Province Key Laboratory of Display Material and Technology, Guangzhou, China

Correspondence should be addressed to Tiberiu Harko

Received 10 July 2017; Accepted 23 August 2017; Published 18 October 2017

Academic Editor: Orlando Luongo

Copyright © 2017 Juntong Su et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The publication of this article was funded by SCOAP3.

Abstract

We investigate matter creation processes during the reheating period of the early Universe, by using the thermodynamic of open systems. The Universe is assumed to consist of the inflationary scalar field, which, through its decay, generates relativistic matter and pressureless dark matter. The inflationary scalar field transfers its energy to the newly created matter particles, with the field energy decreasing to near zero. The equations governing the irreversible matter creation are obtained by combining the thermodynamics description of the matter creation and the gravitational field equations. The role of the different inflationary scalar field potentials is analyzed by using analytical and numerical methods. The values of the energy densities of relativistic matter and dark matter reach their maximum when the Universe is reheated up to the reheating temperature, which is obtained as a function of the scalar field decay width, the scalar field particle mass, and the cosmological parameters. Particle production leads to the acceleration of the Universe during the reheating phase, with the deceleration parameter showing complex dynamics. Once the energy density of the scalar field becomes negligible with respect to the matter densities, the expansion of the Universe decelerates, and inflation has a graceful exit.