[en] A review is made of the utilization of the Higgs mechanism in spontaneous symmetry breaking. It is shown that such as ideas came from an analogy with the superconductivity phenomenological theory based on a Ginzburg-Landau lagrangean. The symmetry restoration through the temperature influence is studied. (L.C.)

[en] The vacuum energy of GED, as a function of the coupling constant α, is shown to have an absolute minimum at the critical coupling α sub(c) = n/3. The effect of chiral symmetry breaking diminishes as the coupling is increased. We argue that these aspects of the vacuum energy shall remain unaltered beyond the ladder approximation. (author)

[en] We estimate the cross-section for glueball production in peripheral heavy-ion collisions through two-photon and double-Pomeron exchange, at energies that will be available at RHIC and LHC. Glueballs will be produced at large rates, opening the possibility to study decays with very small branching ratios. In particular, we discuss the possibility of observing the subprocess γ γ (PP) -> γ γ. (author). 18 refs., 2 tabs

[en] The mass difference of pions is studied in the standard model, paying particular attention to the short distance QCD contribution, which has been handled following the prescription of Brodsky, de Teramond and Schmidt, leading to a calculable result. (Author)

[en] Heavy-ion collisions ultrarelativistic energies may be used as a powerful source of photons and pomerons. We compute the rates for pseudoscalar meson production through two-photon and two-pomeron scattering, at energies that will be available at RHIC and LHC. Light mesons will mostly be produced by pomeron fusion at large rates, the two processes are comparable for charmed mesons, while electromagnetic production will be dominant for bottom mesons. We discuss the possibility of observing the reaction γγ(P P) → R → γγ, and comment on the particular case where R could be a scalar resonance at 650 MeV. (author)

[en] Arguments are given in favor of a hard asymptotic behavior of dynamically generated masses, its consequences for technicolor models are analyzed and a model is proposed, where effects of flavor changing neutral currents are highly supressed and pseudo Goldstone bosons get masses of O(30-90) GeV. (Author)

[en] The problem of gauge hierarchy in a O(N) model is discussed. It is shown the existence of an upper bound for the hierarchy of order α-¹/₂, as proposed by Gildener. This same constraint appears when the breaking is made by the radiative corrections in a scheme elaborated by Weinberg. It is found that fine tunning or redefinition of coupling constants to improve hieracrchy, as proposed in several papers, cannot be done before the calculation of higher order contributions to the effective potential. (Author)

[en] The Cornwall-Norton model is studied in the strong coupling regime. It is shown that the fermionic self-energy at large momenta behaves as Σ(p) ∼ (m²/p) ln (p/m). We verify that in the strong coupling phase the dynamically generated masses of gauge and scalar bosons are of the same order, and the essential features of the model remain intact. (author)

[en] The existence of a bifurcation point in the Scwinger-Dyson equation of 2+1 dimensional quantum electrodynamics with N fermions, is studied. It is found an evidence for the existence of a critical behavior, such that chiral symmetry breaking may occur only for a small number of flavors. (author)

[en] To estimate realistic cross sections in ultra peripheral heavy ion collisions we must remove effects of strong absorption. One method to eliminate these effects make use of a Glauber model calculation, where the nucleon-nucleon energy dependent cross sections at small impact parameter are suppressed. In another method we impose a geometrical cut on the minimal impact parameter of the nuclear collision (b_min>R₁+R₂, where R_i is the radius of ion 'i'). In this last case the effect of a possible nuclear radius dependence with the energy has not been considered in detail up to now. Here we introduce this effect showing that for final states with small invariant mass the effect is negligible. However when the final state has a relatively large invariant mass, e.g., an intermediate mass Higgs boson, the cross section can decrease up to 50%