When the space curvature dopes the radiant intensity

Light experiences matter as an effective curved space-time. With such a geometrization of the underlying background of electromagnetic waves, I derive and discuss the general form of the radiative-transfer equation in any weakly absorbing, linear or not, static or in motion, participating media. The role played by the geometry of the effective space-time on the energetic balance is highlighted, and, in particular, it is demonstrated that the curvature can give rise to an amazing amplifying effect on the radiant intensity even in the presence of absorption. An application on the problem of expanding dielectric envelopes shows the simplicity of such an approach for solving numerous radiation hydrodynamic problems. (C) 2002 Optical Society of America.