Thermal-energy in robertson-walker universes

Abstract

The covariant functional Schrödinger formalism is used to study thermal equilibrium for a scalar field in Robertson Walker spacetimes. It is found that thermal equilibrium can be maintained for field masses, coupling constants and geometries satisfying a given differential equation, of which the massless conformally coupled case is a solution, but not the only one. The thermal energy is computed; it contains a term which for particular geometries, such as de Sitter spacetime, grows in time.