Winfried Zimdahl¹ and Alexander B. Balakin²

¹ Fachbereich Physik, Universität Konstanz
PF M678, D-78457 Konstanz, Germany
E-mail: [email protected]
² Department of General Relativity and Gravitation
Kazan State University, 420008 Kazan, Russia
E-mail: [email protected]

Received: 16 August 2001 / Accepted: 3 March 2002 / Published: 10 March 2002

Abstract: Introducing an effective refraction index of an isotropic cosmic medium, we investigate the cosmological fluid dynamics which is consistent with a conformal, timelike symmetry of a corresponding "optical" metric. We demonstrate that this kind of symmetry is compatible with the existence of a negative viscous pressure and, consequently, with cosmological entropy production. We establish an exactly solvable model according to which the viscous pressure is a consequence of a self-interacting one-particle force which is self-consistently exerted on the microscopic particles of a relativistic gas. Furthermore, we show that a suficiently high decay rate of the refraction index of an ultrarelativistic cosmic medium results in an in ationary expansion of the universe.

Keywords: general relativity; cosmology; thermohydrodynamics; kinetic theory; inflationary universe.