Cosmological Symmetry Breaking and Generation of Electromagnetic Field

Cosmological phase transitions accompanied by some kind of symmetry breaking would cause the creation of topological defects and the resulting production of primordial magnetic field. Moreover, such a procedure inevitably affects the cosmic background radiation and it may be observed today. Motivated by the existence of stabilized embedded defects in the standard model of elementary interactions, we discuss their application to the cosmological electromagnetic field generation

Scaling Distribution of Axionic Strings and Estimation of Axion Density from Axionic Domain Walls

The damping of the axionic string motion due to the surrounding plasma is estimated by a detailed calculation of the fermion scatter from a global string and it is shown that the friction force on the string can be neglected before the axionic domain wall formation in most cases, which is one of the important necessary conditions for the scaling distribution of the strings. The energy density of the axion produced by the collapse of the axionic domain walls is also evaluated using the axionic string distribution, and it is found to be larger or at least comparable to the axion density which originates from the axionic strings.Comment: 20 pages (LaTeX), 3 figures, eclepsf.sty, revised figure

Phase transitions triggered by quantum fluctuations in the inflationary universe

The dynamics of a second-order phase transition during inflation, which is induced by time-variation of spacetime curvature, is studied as a natural mechanism to produce topological defects of typical grand unification scales such as cosmic strings or global textures. It is shown that their distribution is almost scale-invariant with small- and large-scale cutoffs. Also discussed is how these cutoffs are given

Signal of the pion string at high-energy collisions

We study the possible signals of a pion string associated with the QCD chiral phase transition in LHC Pb - Pb collision at energy $\sqrt{s}=5.5$ TeV. In terms of the Kibble-Zurek mechanism we discuss the production and evolution of the pion string. The pion string is not topologically stable, it decays into neutral pions and sigma mesons which in turn decay into pions. Our results show that all the neutral pions from the pion string are distributed at the low momentum and the ratio of neutral to charged pions from the pion string violates the isospin symmetry. For the momentum spectra of the total pions, the signal from the sigma particle decay which is from the pion string will be affected by the large decay width of the sigma significantly.Comment: 8 pages, 3 figures, one reference added, title changed, version accepted for publication in Phys. Rev.

Effect of Quark Scatter on Baryogenesis by Electroweak Strings

The amount of baryon asymmetry generated by the electroweak strings at a rough estimate is smaller than that generated by the bubble expansion since the collapsing strings cannot cover the whole volume of the universe. However, the interaction cross section of the strings with particles can be larger than the geometrical area of the order of the string thickness. The scattering cross section of quarks from the electroweak strings is calculated using Dirac equation in the string background. It it proportional to the reverse of the momentum perpendicular to the string axis. Thus the effective interaction area can be enhanced at least ten times so that the suppression compared to the first order phase transition scenario might be also improved.Comment: 12 pages (LaTeX), no figure, Astroparticle Physics (1996

Are nontopological strings produced at the electroweak phase transition?

We formulate a local condition for a nontopological defect to be present. We apply it for electroweak strings and estimate the probability of their existence at the Ginzburg temperature. As a result we find strings long enough to serve for baryon-number generation are unlikely to be produced.Comment: 12 pages (REVTeX), no figure, Physical Review Letters in pres