THE VACUUM-VACUUM AMPLITUDE AND BOGOLIUBOV COEFFICIENTS
Nikishov A.I.

Received: July 8, 2002

PACS: 11.55.-m, 12.20.-m

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We consider the problem of fixing the phases of Bogoliubov coefficients in quantum electrodynamics such that the vacuum-vacuum amplitude can be expressed through them. For a constant electric field and particles with spins 0 and 1/2, this is done starting from the definition of these coefficients. Using the symmetry between electric and magnetic fields, we extend the result to a constant electromagnetic field. It turns out that for a constant magnetic field, it is necessary to distinguish the in- and out-states, although they differ only by a phase factor. For a spin-1 particle with the gyromagnetic ratio g=2, this approach fails and we reconsider the problem using the proper-time method.