D-DIMENSIONAL RADIATIVE PLASMA - A KINETIC APPROACH

The covariant kinetic approach for the radiative plasma a mixture of a relativistic moving gas plus radiation quanta (photons, neutrinos or gravitons) is generalized to D spatial dimensions. The operational and physical meaning of Eckart's temperature is re-examined. The D-dimens ional expressions for the transport coefficients (heat conduction, bul k and shear viscosity) are evaluated in dosed form. Weinberg's conclus ion that the mixture behaves like a relativistic imperfect simple flui d (in Eckart's formulation) depends neither on the number of spatial d imensions nor on the details of the collisional term. The case of Thom son scattering is studied in detail. In the case where Thomson scatter ing dominates, the bulk viscosity is negligible regardless of the numb er of spatial dimensions. The interest of these results and some of th eir consequences for higher-dimensional cosmologies are also discussed .