Vacuum instability and pair nucleation in a dissipative medium

We present a systematic and interdisciplinary treatment of the problem of spontaneous nucleation of particle-antiparticle pairs in a (2+1)-dimensional system, due to a static and uniform electromagnetic-like held in the presence of quantum dissipation. We present a direct derivation of the Caldeira-Leggett type of mechanism for quantum dissipation within the context of string theory, pointing out the differences between the physical situation in which vacuum decay can occur in a dissipative medium and that of a relativistic string theory giving rise to the Born-Infeld effective action. We then evaluate in detail the particle-antiparticle pair production rate in e dissipative medium. The discussion is specialized to the case in which a background periodic potential is also present, a situation giving rise to interesting resonances between nucleation and lattice-parameter length scales. The theory of dissipative pair nucleation in a periodic potential is worked out in detail, implementing a renormalization-group-ype solution of the problem of quantum dynamics in the presence of a dissipation-driven localization transition which interferes with the effect of the driving electric-like field. The calculation is adapted to take into account also the possible Coulomb-like particle-antiparticle attraction. We hint at a possible application of our theory to the problem of the decay of a supercurrent in a superconducting thin film due to vortex-antivortex nucleation in the presence of a pinning lattice.