Isotropic quantum plasmas

The case of an isotropic plasma, and more specifically a thermal plasma, is of particular interest for dispersion in a plasma. Dispersion in a relativistic quantum plasma differs from dispersion in a nonquantum plasma due to four effects: the quantum recoil, dispersion associated with pair creation, degeneracy, and the effects of the spin of the particles. In this chapter the general theory for dispersion in a relativistic quantum electron gas, presented in §8.3, is applied to an isotropic electron gas, and to the specific case of a FermiDirac (thermal) distribution. Both the degenerate and nondegenerate limits for a Fermi-Dirac distribution are treated in detail. The results are used to discuss the properties of longitudinal and transverse waves in such plasmas. The electrons are assumed unpolarized; spin-dependent effects are discussed separately in §10.2.