Аннотация:We study the massless limit in synchrotron radiation and one-photon pair creation in
magnetic field. In this limit Schwinger critical field H0 = m2c3/(e) tends to zero, so two
characteristic quantum parameters η = H/H0, χ = ηE/mc2 are infinite, and the standard
approximations used in analytical calculations fail. Applying Schwinger’s proper
time methods we derive simple expressions for synchrotron radiation spectra emitted by
massless charges of spins s = 0, 1/2 and the pair creation probability distribution in
the quasiclassical (high Landau levels) regime exhibiting simple scaling properties and
possessing universal spectral shapes.