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)-d imensional system, due to a static and uniform electromagnetic-like he ld in the presence of quantum dissipation. We present a direct derivat ion of the Caldeira-Leggett type of mechanism for quantum dissipation within the context of string theory, pointing out the differences betw een the physical situation in which vacuum decay can occur in a dissip ative medium and that of a relativistic string theory giving rise to t he Born-Infeld effective action. We then evaluate in detail the partic le-antiparticle pair production rate in e dissipative medium. The disc ussion is specialized to the case in which a background periodic poten tial is also present, a situation giving rise to interesting resonance s between nucleation and lattice-parameter length scales. The theory o f dissipative pair nucleation in a periodic potential is worked out in detail, implementing a renormalization-group-ype solution of the prob lem of quantum dynamics in the presence of a dissipation-driven locali zation transition which interferes with the effect of the driving elec tric-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.