Publications

Abstract

The transfer of radiation in an isotropic refractive, and dispersive medium in a curved spacetime is studied by applying thegeneral-relativistic kinetic theory. Relativistic geometric optics in a dispersive medium is first analyzed; in particular, the change of frequency along the ray and the change of the direction of propagation as observed in the local rest frame of the medium are studied. The general-relativistic kinetic theory is then shown to be extendable to photons in a dispersive medium. Assuming that the radiation only undergoes continuous refraction and dispersion, the law of change of specific intensity along the ray can be obtained easily. The transfer of blackbody radiation, the propagation of radiation in a cold plasma in the Friedmann universe, and the derivation of the explicit form of the transfer equation in a spherically symmetric nonstationary dispersive medium are discussed as examples. Some astrophysical situations are indicated in which both refractive and dispersive effects of a medium and the effects of the gravitational field on the radiation can be important.