The dynamics of partons that emerge as the result of quantum tunneling in a
spatially uniform time-dependent field is studied under conditions prevale
nt in ultrarelativistic heavy-ion collisions. A self-consistent set of coup
led equations that consists of the renormalized Maxwell equation and the Vl
asov kinetic equation that involves a source and which is derived on a dyna
mical basis is solved numerically. The time dependence of the distributions
of internal fields and currents for bosons and fermions is investigated wi
thin this back-reaction mechanism, and their momentum spectra are construct
ed. Clear evidence that oscillations in the time dependence of parton distr
ibutions in phase-space cells are of a stochastic character is obtained, an
d a significant irregularity in the momentum distribution on large time sca
les is found. If the influence of the back reaction is disregarded, these e
ffects disappear completely, the oscillations becoming regular. A possible
thermalization scenario for such a quasiparticle plasma is considered in th
e relaxation-time approximation. A locally equilibrium state is described w
ithin the two-component thermodynamics of particles and antiparticles. The
possibility of introducing temperature under conditions of a strong vacuum
polarization is discussed. (C) 2001 MAIK "Nauka/Interperiodica".