DYNAMICS OF COSMOLOGICAL PERTURBATIONS IN THERMAL LAMBDA-PHI(4) THEORY

Using a recent thermal-field-theory approach to cosmological perturbat ions, the exact solutions that were found for collisionless ultrarelat ivistic matter are generalized to include the effects from weak self-i nteractions in a lambda phi(4) model through order lambda(3/2). This i ncludes the effects of a resummation of thermal masses and associated nonfocal gravitational vertices, thus going far beyond classical kinet ic theory. Explicit solutions for all the scalar, vector, and tensor m odes are obtained for a radiation-dominated Einstein-de Sitter model c ontaining a weakly interacting scalar plasma with or without the admix ture of an independent component of perfect radiation fluid.