Showing papers by "Graciela B. Gelmini published in 1996"

Cosmology and astroparticles

Abstract: These lectures are devoted to elementary particle physicists and assume the reader has very little or no knowledge of cosmology and astrophysics. After a brief historical introduction to the development of modern cosmology and astro‐particles in which the Hot Big Bang model is defined, the Robertson‐Walker metric and the dynamics of the Friedmann‐Robertson‐Walker cosmology are discussed in section 2. In section 3 the main observational features of the Universe are reviewed, including a description of our neighborhood, homogeneity and isotropy, the cosmic background radiation, the expansion, the age and the matter content of the Universe. A brief account of the thermal history of the Universe follows in section 4, and relic abundances are discussed in section 5. Section 6 is devoted to primordial nucleosynthesis, section 7 to structure formation in the Universe and section 8 to the possibility of detection of the dark matter in the halo of our galaxy. In the relevant sections recent developments are included, such as several so called ‘‘crisis’’ (the age crisis, the cluster baryon crisis and the nucleosynthesis crisis), and the MACHO events that may constitute the first detection of dark matter in the halo of our galaxy.

Cosmology and Astroparticles

Abstract: Talks given at the V Taller de Particulas y Campos (V-TPyC) and V Taller Latinoam. de Fenomenologia de las Interac. Fundam. (V-TLFIF), Puebla, Mexico, 10/30 - 11/3 1995. These lectures are devoted to elementary particle physicists and assume the reader has very little or no knowledge of cosmology and astrophysics. After a brief historical introduction to the development of modern cosmology and astro-particles in which the Hot Big Bang model is defined, the Robertson-Walker metric and the dynamics of the Friedmann-Robertson-Walker cosmology are discussed in section 2. In section 3 the main observational features of the Universe are reviewed, including a description of our neighbourhood, homogeneity and isotropy, the cosmic background radiation, the expansion, the age and the matter content of the Universe. A brief account of the thermal history of the Universe follows in section 4, and relic abundances are discussed in section 5. Section 6 is devoted to primordial nucleosynthesis, section 7 to structure formation in the Universe and section 8 to the possibility of detection of the dark matter in the halo of our galaxy.

Strange Baryonic Matter from Chiral Effective Lagrangians

Abstract: We investigate the existence of bound states of baryons in a kaon condensate using chiral mean field theory. The interactions are described by an effective SU(3)_L X SU(3)_R chiral lagrangian where terms of higher order in density, baryon momentum, and kaon mass are suppressed by powers of the symmetry breaking scale, Lambda. We take up to next to leading order terms (n = 2,3,4). We search for infinite baryon number solutions, namely ``strange baryonic matter'', using a Thomas-Fermi approximation for a slowly varying condensate and a lowest order Hartree approximation to describe the many body interactions. For simplicity we study a pure K^0 condensate and only neutrons, the lightest baryons in that condensate. We find solutions with neutron number densities, rho_n > 3.5 rho_0, where rho_0 is the infinite nuclear matter density. This is consistent with the estimate of the onset of a K-condensate at rho_n = 2-4 rho_0. We show that the binding energies, E_b, grow with rho_n and for rho_n 7 rho_0 perturbative expansion is lost) we find E_b < 150 MeV (E_b < 70 MeV for rho_n < 5 rho_0) even in the most favorable cases. These binding energies may be too low for this type of matter to appear and persist in the early universe.