Nonperturbative Physics in a Magnetic Field

Non-Perturbative Quantum Field Theory has played an important role in the study of phenomena where a fermion condensate can appear under certain physical conditions. The familiar phenomenon of electric superconductivity, the color superconductivity of very dense quark matter, and the chiral symmetry breaking of low energy effective chiral theories are all examples of that sort. Often one is interested in the behavior of these systems in the presence of an external magnetic field. In this talk I will outline the effects of an external magnetic field on theories with either fermion-fermion or fermion-antifermion condensates.Comment: Invited talk at XII Mexican Workshop on Particles & Fields. Mazatlan, Sinaloa, Mexico, Nov.200

Yukawa Interactions and Dynamical Generation of Mass in an External Magnetic Field

In this work we study the dynamical generation of a fermion mass induced by a constant and uniform external magnetic field in an Abelian gauge model with a Yukawa term. We show that the Yukawa coupling not only enhances the dynamical generation of the mass, but it substantially decreases the magnetic field required for the mass to be generated at temperatures comparable to the electroweak critical temperature. These results indicate that if large enough primordial magnetic fields were present during the early universe evolution, the field-induced generation of fermion masses, which in turn corresponds to the generation of fermion bound states, may play an important role in the electroweak phase transition.Comment: Corrected mistake in last reference. Work presented at SILAFAE'98, 8 pages. To be published in the proceedings of SILAFAE'98, April 8-11, San Juan, Puerto Ric

Magnetic Response in Anyon Fluid at High Temperature

The magnetic response of the charged anyon fluid at temperatures lower and larger than the fermion enery gap $\omega_{c}$ is investigated in the self-consistent field approximation. We prove that the anyon system with boundaries exhibits a total Meissner effect at temperatures smaller than the fermion energy gap ($T\ll \omega_{c}$). The London penetration length at $T$ $\sim 200K$ is of the order $\lambda \sim 10^{-5}cm$. At $T\gg \omega_{c}$ a new phase, characterized by an inhomogeneous magnetic penetration, is found. We conclude that the energy gap, $\omega_{c},$ defines a scale that separates two phases: a superconducting phase at $T\ll \omega_{c}$, and a non-superconducting one at $T\gg \omega_{c}$.Comment: 7 pages, Talk presented at SILAFAE'98. April 8-11, 1998, San Juan, Puerto Ric