COVARIANT FORMULATION OF PHOTON ACCELERATION

We present, a covariant theory of photon acceleration in time-varying plasmas. This is a ray-tracing model for frequency upshift of waves in teracting with relativistic plasma perturbations, such as ionization f ronts and plasma wakefields. This theory explores the formal analog; b etween a photon in a plasma and a relativistic particle with a finite rest mass. The covariant ray-tracing theory is applied to the case of photon acceleration by a modulated wakefield. Threshold criteria for t ransition to chaos are derived.