Particle creation from vacuum by a homogeneous electric field in the canonical formalism

The paper is concerned with particle creation from vacuum by a homogeneous electric field that depends arbitrarily on the time. Diagonalizing the Hamiltonian by Bogoiyubov transformations, we obtain exact formulas for the probability of creation of both fermion and boson pairs. The formulas are applied to special cases. The vacuum of quasiparticles in the limit $t\to\infty$ is interpreted as a condensate consisting of particle-anti particle pairs with vanishing total momentum. The classical characteristics of this condensate are studied.