58 research outputs found
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
Absence of Landau-Peierls Instability in the Magnetic Dual Chiral Density Wave Phase of Dense QCD
We investigate the stability of the Magnetic Dual Chiral Density Wave (MDCDW)
phase of cold and dense QCD against collective low-energy fluctuations of the
order parameter. The appearance of additional structures in the system
free-energy due to the explicit breaking of the rotational and isospin
symmetries by the external magnetic field and the field-induced asymmetry of
the lowest Landau level modes play a crucial role in the analysis. The new
structures not only affect the condensate minimum equations, but also the
spectrum of the thermal fluctuations, which lacks the transverse soft modes
that typically affect single-modulated inhomogeneous phases in the absence of a
magnetic field. Consequently, the long-range order of the MDCDW phase is
preserved at finite temperature. The lack of Landau-Peierls instabilities in
the MDCDW phase makes this inhomogeneous phase of dense quark matter
particularly relevant for the physics of neutron stars.Comment: Typos corrected, new discussions adde
Neutrinos under Strong Magnetic Fields
In this talk we review the results on neutrino propagation under external
magnetic fields. We concentrate on the effects of strong magnetic fields
in neutral media. It is shown that the neutrino
energy density get a magnetic contribution in the strong-field, one-loop
approximation, which is linear in the Fermi coupling constant as in the charged
medium. It is analyzed how this correction produces a significant oscillation
resonance between electron-neutrinos and the other two active flavors, as well
as with sterile neutrinos. The found resonant level-crossing condition is
highly anisotropic. Possible cosmological applications are discussed. Effects
due to primordial hypermagnetic fields on neutrinos propagating in the
symmetric phase of the electroweak model are also presented. At sufficiently
strong hypermagnetic fields, , the neutrino energy is found to be
similar to that of a massless charged particle with one-degree of freedom.Comment: Talk given at the Fourth Tropical Workshop on Particle Physics and
Cosmology, Cairns, Australia, June 9-13, 200
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