Strangelets and their possible astrophysical origin

We discuss the first-order phase transition of QCD at high temperature in the universe and the possible formation of quark-matter lumps through cooling in regions of increased pressure. We show tha similarity of results using confinement and breaking of chiral symmetry. The inclusion of strange matter may give stability to small drops, or strangelets, in the colour-flavour locked phase possibly achieved in neutron stars that could reach a high-altitude observatory like that of Chacaltaya as primary cosmic rays.Comment: 7 pages, latex, no figure

Strings With Axionic Content and Baryogenesis

We describe different electroweak strings with axionic content, including non-topological configurations calculated numerically, and show their possible influence on baryogenesis indicating that they may constitute a mechanism competitive to that of bubble nucleation with two Higgs-doublets.Comment: 12 page

Hard component of ultra-high energy cosmic rays and vortons

Observed events of ultra-high energy cosmic rays may indicate a hard component for the energy spectrum of their flux, which might have origin in the decay of long-lived vortons presumably condensed in the galactic halo. To be consistent with the needed present density, vortons may have been formed during the breaking of an abelian symmetry contained in a large GUT group like E6 and a part of them could have survived the destabilization caused by the electroweak transition.Comment: accepted version to appear in Astroparticle Physics. 24 pages, 3 figures. Enlarged discussion on vortons formation and GUT model

Influence of Strings with Axionic Content on the Polarization of Extragalactic Sources

It is shown that the axion concentrated in electroweak strings which are consequently stabilized may produce a rotation of the polarization angle of radiation from extragalactic sources larger than that caused by a background field, and that axionic walls attached to global strings have an effect which depends on the frequency. We discuss the validity of the classical and quantum treatments of radiation and indicate that the latter produces conversion of linear into circular polarization. We describe possible anomalies in the observations which might suggest these influences of the axion.Comment: 11 pages, latex, no figure

Comparison of UHECR spectra from necklaces and vortons

Cosmic rays of energy higher than 10^19 eV may be explained by topological defects produced in the early stages of universe. Two suitable alternatives are: necklaces formed by magnetic monopoles connected by strings, and vortons which are loops stabilized by superconducting currents. The former are uniformly distributed in the universe, may account for cosmic rays above the ankle, suffer a transient GZK cutoff with a subsequent recovery and isotropy of observations is expected. The latter are concentrated in the galactic halo, require an additional extragalactic contribution between the ankle and the GZK cutoff, beyond which give a harder component and predict anisotropy related to mass concentration.Comment: 11 pages, standard latex, 3 postscript figures. Presented at the Chacaltaya Meeting on Cosmic Rays Physics, La Paz, 23-27 July 200