Spin radiative corrections to the radiation probability and power in classical and quantum electrodynamics

Abstract

Spin radiative effects in a one-particle sector of QED have a dual nature and can be understood with the Frenkel classical rotating-electron model. In the region of parameters under study γ_⊥ ² ≫ 1 (γ_⊥ ² = 1 + p _⊥ ²/m ²) and χ ≪ 1 (χ = ${{\sqrt {{{\left( {e{F_{\mu v}}{p_v}} \right)}^2}} } \mathord{\left/ {\vphantom {{\sqrt {{{\left( {e{F_{\mu v}}{p_v}} \right)}^2}} } {{m^3}}}} \right. \kern-\nulldelimiterspace} {{m^3}}}$), the imaginary part of the mass shift and radiation power contain two types of spin contributions. The contributions of the first type are related to the intrinsic magnetic moment of a fermion representing an additional source of electromagnetic radiation. The contributions of the second type have the opposite sign and are caused by a small change in the electron acceleration appearing due to the Frenkel addition to the particle mass. Contributions of the second type dominate, which explains the “wrong” sign of total spin corrections. We show that not only the sign but also the values of coefficients can be explained with specified accuracy using classical electrodynamics if corrections to the mass shift (action) and radiation power are calculated in canonical variables, i.e., for fixed velocity and momentum values, respectively. The results can be treated as a demonstration of the correspondence principle in the field of radiative spin effects, in addition to correspondence between classical and quantum theories at the tree (in the external filed) level. For a _e ≡ (g–2)/2 ≲ χ ≪ 1, equations of the Frenkel model lead to generalization of the system of Lorentz–BMT (Bargmann–Michel–Telegdi) equations taking into account the Frenkel addition to mass. Some features of experimental observations of the spin light are discussed.