https://repositorio.ufba.br/handle/ri/10580 2026-05-04T18:43:11Z https://repositorio.ufba.br/handle/ri/16298 Título: Magnetic effects on spontaneous symmetry breaking/restoration in a toroidal topology Autor(es): Abreu, Luciano Melo; Linhares, C. A.; Malbouisson, Adolfo Pedro Carvalho; Malbouisson, Jorge Mário Carvalho Abstract: We study temperature and finite-size effects on the spontaneous symmetry breaking/restoration for a scalar field model under the influence of an external magnetic field, at finite chemical potential.We use the two-particle irreducible formalism and consider the large-N limit. We find that there is a minimal size of the system to sustain the broken phase, which diminishes as the applied field increases but is independent of the chemical potential. We analyze the critical curves and show that the magnetic field enhances the broken-phase regions, while increasing the chemical potential leads to a diminishment of the critical temperature. Editora / Evento / Instituição: American Physical Society Tipo: Artigo de Periódico 2013-01-01T00:00:00Z https://repositorio.ufba.br/handle/ri/16279 Título: Heavy flavor relaxation in a hadronic medium Autor(es): Cabrera, Daniel; Abreu, Luciano Melo; Llanes-Estrada, Felipe J.; Torres-Rincon, Juan M. Abstract: Charm and bottom transport coefficients in a medium constituted of light mesons, such as is formed in the hadronic phase of heavy-ion collisions, are obtained within an effective field theory approach implementing heavy-quark symmetry and chiral symmetry breaking. Heavy flavor propagates in the medium as D/B and D*/B* degrees of freedom, and unitarization of the lowest order heavy–light meson amplitudes is used in order to reach high temperatures. The latter accounts for dynamically generated resonances in isospin 1/2 channels, a feature that leads to a more efficient heavy-flavor diffusion. We discuss the temperature and momentum dependence of the friction and diffusion coefficients in a transport approach up to temperatures of about T 150 MeV, and provide estimates of the charm/bottom relaxation lengths and momentum loss. Implications for heavy-meson spectrum observables in heavy-ion collisions are discussed. Editora / Evento / Instituição: Elsevier Tipo: Artigo de Periódico 2013-01-01T00:00:00Z https://repositorio.ufba.br/handle/ri/16275 Título: Thermodynamic behavior of the generalized scalar Yukawa model in a magnetic background Autor(es): Abreu, Luciano Melo; Malbouisson, A. P. C.; Malbouisson, J. M. C.; Nery, E. S.; Silva, R. Rodrigues da Abstract: We study the thermodynamic behavior of the generalized scalar Yukawa model, composed of a complex scalar field interacting with scalar and vector fields. Thermal effects are treated in the framework of generalized zeta-functions. For the case of vanishing effective chemical potential, we find a vanishing contribution from the vector field. We focus on the analysis of the phase structure of this model at effective chemical equilibrium, under change of values of the relevant parameters of the model, looking specially to the influence of the magnetic background on the phase structure. Editora / Evento / Instituição: Elsevier Tipo: Artigo de Periódico 2014-01-01T00:00:00Z https://repositorio.ufba.br/handle/ri/14740 Título: Transport properties of bottomed mesons in a hot mesonic gas Autor(es): Abreu, Luciano Melo; Cabrera, Daniel; Torres-Rincon, Juan M. Abstract: In this work we evaluate the B-meson drag and diffusion coefficients in a hot medium constituted of light mesons (π, K, K⎯⎯⎯, and η). We treat the B-meson and B*-meson interactions with pseudo-Goldstone bosons in chiral perturbation theory at next-to-leading order within the constraints from heavy quark symmetry and employ standard unitarization techniques of next-to-leading order amplitudes in order to account for dynamically generated resonances (leading to a more efficient heavy-flavor diffusion) and thus reach higher temperatures. We estimate individual meson contributions from the gas to the transport coefficients and perform a comparison with other findings in literature. We report a bottom relaxation length of about 80 fm at a temperature of 150 MeV and for typical momenta of 1 GeV, at which our approach is reliable. Compared to a charm relaxation length of 40 fm in the same conditions, we conclude that the B mesons provide a cleaner probe of the early stages of a heavy-ion collision. Editora / Evento / Instituição: American Physical Society Tipo: Artigo de Periódico 2013-01-01T00:00:00Z