Ruiz Ruiz, Fernando2023-06-202023-06-201989-03-230370-269310.1016/0370-2693(89)91086-1https://hdl.handle.net/20.500.14352/59051Copyright © 1989 Published by Elsevier B.V.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.journal articlehttp://dx.doi.org/10.1016/0370-2693(89)91086-1http://www.sciencedirect.commetadata only access53PhysicsMultidisciplinaryFísica (Física)22 Física