Friction in inflaton equations of motion

Abstract

The possibility of a friction term in the equation of motion for a scalar field is investigated in non-equilibrium field theory. The results obtained differ greatly from existing estimates based on linear response theory, and suggest that dissipation is not well represented by a term of the form $\eta \dot{\varphi }$.

Comments: 4 pages, 2 figures, RevTex4. An obscurity in the original version has been clarified