Analytic Solution of the Boltzmann Equation in an Expanding System

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Abstract
For a massless gas with a constant cross section in a homogeneous, isotropically expanding spacetime we reformulate the relativistic Boltzmann equation as a set of nonlinear coupled moment equations. For a particular initial condition this set can be solved exactly, yielding the first analytical solution of the Boltzmann equation for an expanding system. The nonequilibrium behavior of this relativistic gas can be mapped onto that of a homogeneous, static nonrelativistic gas of Maxwell molecules.
Funding Information
  • Conselho Nacional de Desenvolvimento Científico e Tecnológico
  • Fundação de Amparo à Pesquisa do Estado de São Paulo
  • U.S. Department of Energy (DE-SC0012704)
  • Natural Sciences and Engineering Research Council of Canada
  • Office of Science
  • Nuclear Physics (DE-SC0004286)
  • Ohio State University