Electron mass shift in nonthermal systems

The electron mass is known to be sensitive to local fluctuations in the electromagnetic field, and undergoes a small shift in a thermal field. It was claimed recently that a very large electron mass shift should be expected near the surface of a metal hydride [{\it Eur. Phys. J. C}, {\bf 46} 107 (2006)]. We examine the shift using a formulation based on the Coulomb gauge, which leads to a much smaller shift. The maximization of the electron mass shift under nonequilibrium conditions seems nonetheless to be an interesting problem. We consider a scheme in which a current in a hollow wire produces a large vector potential in the wire center. Fluctuations in an LC circuit with nearly matched loss and gain can produce large current fluctuations; and these can increase the electron mass shift by orders of magnitude over its room temperature value.