Kinetic equations for ultrarelativistic particles in a Robertson-Walker Universe and isotropization of relict radiation by gravitational interactions

TL;DR

This paper derives kinetic equations for ultrarelativistic particles considering gravitational interactions in a Robertson-Walker universe, concluding that relic radiation is highly uniform on small scales.

Contribution

It introduces new kinetic equations accounting for gravitational interactions in an expanding universe, providing insights into relic radiation isotropization.

Findings

Relic radiation is highly uniform on scales less than 10 arcminutes.

Derived kinetic equations incorporate gravitational effects for ultrarelativistic particles.

The solutions suggest a high degree of isotropy in relic radiation.

Abstract

Kinetic equations for ultrarelativistic particles with due account of gravitational interactions with massive particles in the Robertson-Walker universe are obtained. On the basis of an exact solution of the kinetic equations thus obtained, a conclusion is made as to the high degree of the uniformity of the relict radiation on scales with are less than $10'$.