Chiral Symmetry
Mostrando 1-12 de 27 artigos, teses e dissertações.
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1. The role of crossing symmetry for a low energy pion-nucleon scattering from dispersive method
The slow convergence of chiral perturbation theory for heavy baryons (HBChPT) suggests that any attempt to unitarize the amplitude following from this method will fail to describe the experimental phase shifts. However, it was possible to obtain a ChPT pion nucleon amplitudes respecting exact unitarity relation by using the Inverse Amplitude Method (IAM), bu
Brazilian Journal of Physics. Publicado em: 2008-09
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2. Thermal properties of heavy-light quark pseudoscalar and vector mesons
The thermal behaviour of the mass, leptonic decay constant, and width of heavy-light quark peseudoscalar and vector mesons is analized in the framework of thermal Hilbert moment QCD sum rules. In all the cases, the meson leptonic decay constants decrease with increasing T, and vanish at a critical temperature Tc, while the mesons develop a width which increa
Brazilian Journal of Physics. Publicado em: 2008-09
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3. Scalar resonance: A model for Kappa / Ressonâncias escalares: Um modelo para o Kappa
O objetivo principal desta dissertação é estudar a ressonância $\k$, um méson escalar ainda hoje bastante controverso na comunidade científica. Estudamos o espalhamento elástico $K\pi$, pois é neste subsistema que o $\k$ se manifesta como um estado intermediário. A partir de uma lagrangiana efetiva quiral $SU(3)\times SU(3)$, envolvendo termos de co
Publicado em: 2008
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4. Connecting an effective model of confinement and chiral symmetry to lattice QCD
We construct an effective model for the chiral field and the Polyakov loop in which we can investigate the interplay between the approximate chiral symmetry restoration and the deconfinement of color in a thermal SU(3) gauge theory with three flavors of massive quarks. The phenomenological couplings between these two sectors can then be related to the recent
Brazilian Journal of Physics. Publicado em: 2007-03
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5. Is the chiral phase transition induced by a metal-insulator transition?
We investigate the QCD Dirac operator with gauge configurations given by a liquid of instantons in the region of temperatures about the chiral phase transition. Both the quenched and unquenched cases are examined in detail. We present evidence of a localization transition in the low lying modes of the Dirac operator around the same temperature as the chiral
Brazilian Journal of Physics. Publicado em: 2007-03
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6. Gauge Covariance and the Chiral Condenate in QED3
The ambiguities associated with the lack of gauge invariance in the non-perturbative truncations of Schwinger-Dyson equations (SDEs) are a challenging problem which has not yet been resolved in a decisive fashion. Pursuing this aim, we study dynamical chiral symmetry breaking in quantum electrodynamics in three space-time dimensions (QED3). We investigate th
Brazilian Journal of Physics. Publicado em: 2007-03
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7. Linear sigma model at finite baryonic density and symmetry breakings
The linear sigma model at finite baryonic density with a massive vector field is investigated considering that all the bosonic fields develop non zero expected classical values, eventually associated with condensates and corresponding to dynamical symmetry breakings which might occur in the QCD phase diagram. A modified equation for the classical vector fiel
Brazilian Journal of Physics. Publicado em: 2007-03
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8. QCD Green functions and their application to hadron physics
In a functional approach to QCD the infrared behaviour of Landau gauge Green functions is investigated. It can be proven that the ghost Dyson-Schwinger equation implies the Gribov-Zwanziger horizon condition. Its relation to the Kugo-Ojima confinement scenario is elucidated. Positivity violation for gluons is demonstrated, and the analytic structure of the g
Brazilian Journal of Physics. Publicado em: 2007-03
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9. Chiral symmetry restoration and pion properties in a q-deformed NJL model
We review the implementation of a q-deformed fermionic algebra in the Nambu-Jona-Lasinio model (NJL). The gap equations obtained from a deformed condensate as well as from the deformation of the NJL Hamiltonian are discussed. The effect of both temperature and deformation in the chiral symmetry restoration process as well as in the pion properties is studied
Brazilian Journal of Physics. Publicado em: 2006-03
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10. Transporte em nanoestruturas: mÃtodos de movimento Browniano e teoria de circuitos
The results presented in this thesis can be divided into two parts. In the first one we study a class of Brownian motion ensembles (BME) obtained from the general theory of matricial Markovian stochastic processes of random matrix theory. The ensembles are characterized by a Fokker-Planck equation and are closely related to Hamiltonians of Calogero-Sutherlan
Publicado em: 2006
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11. Os termos sigma do núcleon e da delta / Nucleon and Delta sigma-terms
O termo sigma do núcleon, $sigma_N$, pode ser extraído dos dados experimentais e permite testar teorias e modelos que buscam descrever os efeitos da quebra explícita de simetria quiral sobre o núcleon. A teoria de perturbação quiral é considerada atualmente a teoria efetiva da cromodinâmica quântica, sendo destinada a descrever o regime de baixas en
Publicado em: 2006
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12. Quark matter in a QCD Coulomb gauge quark model
In this communication we present results of a study of chiral symmetry in quark matter using an effective Coulomb gauge QCD Hamiltonian. QCD in Coulomb gauge is convenient for a variational approach based on a quasiparticle picture for the transverse gluons, in which a confining Coulomb potential arises naturally. We show that such an effective Hamiltonian p
Brazilian Journal of Physics. Publicado em: 2005-09