Ferromagnetic properties of charged vector bosons condensate in the early universe

Bose-Einstein condensation in the early universe is considered. The magnetic properties of a condensate of charged vector bosons are studied, showing that a ferromagnetic state is formed. As a consequence, the primeval plasma may be spontaneously magnetized inside macroscopically large domains and primordial magnetic fields can be generated.Comment: 4 pages IAU Symposium 274, 6-10 September 2010, Giardini Naxos, Italy; Published in Proceedings of the International Astronomical Union, 2011, Advances in Plasma Astrophysics, A. Bonanno, E. de Gouveia Dal Pino & A. Kosovichev, eds., Cambridge Univerity Pres

Electrodynamics at non-zero temperature, chemical potential, and Bose condensate

Electrodynamics of charged scalar bosons and spin 1/2 fermions is studied at non-zero temperature, chemical potentials, and possible Bose condensate of the charged scalars. Debye screening length, plasma frequency, and the photon dispersion relation are calculated. It is found that in presence of the condensate the time-time component of the photon polarization operator in the first order in electric charge squared acquires infrared singular parts proportional to inverse powers of the spatial photon momentum k.Comment: Two references and explanatory comments are added according to the referee's suggestions. The paper is accepted for publication in JCA

Warm inflation in presence of magnetic fields

We present preliminary results on the possible effects that primordial magnetic fields can have for a warm inflation scenario, based on global supersymmetry, with a new-inflation-type potential. This work is motivated by two considerations: first, magnetic fields seem to be present in the universe on all scales, which rises the possibility that they could also permeate the early universe; second, the recent emergence of inflationary models where the inflaton is not assumed to be isolated but instead it is taken as an interacting field, even during the inflationary expansion. The effects of magnetic fields are included resorting to Schwinger proper time method.Comment: Published in AIP Conf. Proc. 1548, 288 (2013), IX Mexican School on Gravitation and Mathematical Physics: Cosmology for the XXIst Centur

Effective potential at finite temperature in a constant hypermagnetic field: Ring diagrams in the Standard Model

We study the symmetry breaking phenomenon in the standard model during the electroweak phase transition in the presence of a constant hypermagnetic field. We compute the finite temperature effective potential up to the contribution of ring diagrams in the weak field, high temperature limit and show that under these conditions, the phase transition becomes stronger first order.Comment: 15 pages, 8 Postscript figure

Feynman parametrization and Mellin summation at finite temperature

We show that the Mellin summation technique (MST) is a well defined and useful tool to compute loop integrals at finite temperature in the imaginary-time formulation of thermal field theory, especially when interested in the infrared limit of such integrals. The method makes use of the Feynman parametrization which has been claimed to have problems when the analytical continuation from discrete to arbitrary complex values of the Matsubara frequency is performed. We show that without the use of the MST, such problems are not intrinsic to the Feynman parametrization but instead, they arise as a result of (a) not implementing the periodicity brought about by the possible values taken by the discrete Matsubara frequencies before the analytical continuation is made and (b) to the changing of the original domain of the Feynman parameter integration, which seemingly simplifies the expression but in practice introduces a spurious endpoint singularity. Using the MST, there are no problems related to the implementation of the periodicity but instead, care has to be taken when the sum of denominators of the original amplitude vanishes. We apply the method to the computation of loop integrals appearing when the effects of external weak magnetic fields on the propagation of scalar particles is considered.Comment: 16 pages, 1 figure. Discussion expanded. References added. Published versio