Repulsive Core of NN S-Wave Scattering in a Quark Model with a Condensed Vacuum

We work in a chiral invariant quark model, with a condensed vacuum, characterized by only one parameter. Bound state equations for the nucleon and Delta are solved in order to obtain an updated value of their radii and masses. Nucleon-nucleon S-Wave scattering is studied in the RGM framework both for isospin T=1 and T=0. The phase shifts are calculated and an equivalent local potential, which is consistent with K-N scattering, is derived. The result is a reasonable microscopic short range repulsion in the nucleon-nucleon interaction.Comment: 23 pages in latex revtex, 4 Postscript figure

A new Perspective on the Scalar meson Puzzle, from Spontaneous Chiral Symmetry Breaking Beyond BCS

We introduce coupled channels of Bethe-Salpeter mesons both in the boundstate equation for mesons and in the mass gap equation for chiral symmetry. Consistency is insured by the Ward Identities for axial currents, which preserve the Goldstone boson nature of the pion and prevents a systematic shift of the hadron spectrum. We study the decay of a scalar meson coupled to a pair of pseudoscalars. We also show that coupled channels reduce the breaking of chiral symmetry, with the same Feynman diagrams that appear in the coupling of a scalar meson to a pair of pseudoscalar mesons. Exact calculations are performed in a particular confining quark model, where we find that the groundstate $I=0, ^3P_0 q \bar q$ meson is the f_0(980) with a partial decay width of 40MeV. We also find a 30% reduction of the chiral condensate due to coupled channels.Comment: 17 pages, Revtex, 8 eps figures, and several eps diagrams in equation

Vacuum replicas in QCD

The properties of the vacuum are addressed in the two- and four-dimensional quark models for QCD. It is demonstrated that the two-dimensional QCD ('t Hooft model) possesses only one possible vacuum state - the solution to the mass-gap equation, which provides spontaneous breaking of the chiral symmetry (SBCS). On the contrary, the four-dimensional theory with confinement modeled by the linear potential supplied by the Coulomb OGE interaction, not only has the chirally-noninvariant ground vacuum state, but it possesses an excited vacuum replica, which also exhibits SBCS and can realize as a metastable intermediate state of hadronic systems. We discuss the influence of the latter on physical observables as well as on the possibility to probe the vacuum background fields in QCD.Comment: RevTeX4, 26 pages, 8 EPS figures, extended references, corrected some typos, to appear in Phys.Rev.

Apparent digestibility of conventional and alternative feedstuffs by hybrid tambacu juveniles.

Abstract: The apparent digestibility coefficients (ADC's) of dry matter (DM), crude protein (CP), and gross energy (GE) of conventional feedstuffs (cottonseed meal-CSM, soybean meal-SBM, wheat bran-WHB, corn-COR) and regional alternative feedstuffs (common bean residue meal-CBR, mesquite meal-MES, pasta by-product meal-PBM) were determined for hybrid juvenile tambacu Colossoma macropomum × Piaractus mesopotamicus. The apparent DM and GE digestibility of feedstuffs decreased (p0.05) were found among ADC's of PBM and COR. The lowest CP ADC among energy sources was observed in MES; the lowest CP ADC among plant protein sources was observed in CBR. Information about the ADC's of conventional and alternative feedstuffs for tambacu is essential to formulate low-cost diets and can contribute to regional development

A Espectroscopia na região do Infravermelho e algumas aplicações.

bitstream/item/88969/1/DOC51-2010.pd

Running coupling and fermion mass in strong coupling QED

Simple toy model is used in order to exhibit the technique of extracting the non-perturbative information about Green's functions in Minkowski space. The effective charge and the dynamical electron mass are calculated in strong coupling 3+1 QED by solving the coupled Dyson-Schwinger equations for electron and photon propagators. The minimal Ball-Chiu vertex was used for simplicity and we impose the Landau gauge fixing on QED action. The solution obtained separately in Euclidean and Minkowski space were compared, the latter one was extracted with the help of spectral technique.Comment: 23 pages, 4 figures, v4: revised and extended version, one introductory section adde

Chiral Extrapolation, Renormalization, and the Viability of the Quark Model

The relationship of the quark model to the known chiral properties of QCD is a longstanding problem in the interpretation of low energy QCD. In particular, how can the pion be viewed as both a collective Goldstone boson quasiparticle and as a valence quark antiquark bound state where universal hyperfine interactions govern spin splittings in the same way as in the heavy quark systems. We address this issue in a simplified model which; however, reproduces all features of QCD relevant to this problem. A comparison of the many-body solution to our model and the constituent quark model demonstrates that the quark model is sufficiently flexible to describe meson hyperfine splitting provided proper renormalization conditions and correct degrees of freedom are employed consistently.Comment: 6 pages, 2 eps figures, uses revtex. Version to appear in Phys. Rev. Let