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[en] The nonperturbative functions parametrizing off-diagonal hadron matrix elements of light-cone leading-twist quark operators are considered. Given functions are calculated in the framework of the presented relativistic quark model with nontrivial structure of QCD vacuum in which the gauge invariance is taken into account. Hadrons are treated as bound states of quarks and the strong quark-hadrons vertices are described by instanton-induced effective Lagrangians of the interaction. The parameters of instanton vacuum, the effective instanton radius and the constituent quark mass are related to the quantity of vacuum expectations of the lowest dimension quark-gluon operators and the low-energy observables of pion

[en] The helicity structure function of the nucleon has been calculated for the constituent quark model and compared to the prediction of the Drell-Hearn-Gerasimov sum rule. The multipole decomposition of the sum rule shows large cancellations between different resonances. The small isoscalar-isovector contribution is revealed top the admixture of D-state ('bag deformation') in the nucleon's wave function. The calculations indicate a relatively slow saturation of this part of the sum rule with excitation energy

[en] First, I summarize the recently proposed idea of leptons and quarks composed of algebraic degrees of freedom (defined by Clifford algebras) that justifies the existence of three and only three replicas of the fundamental fermions (as e.g. e^-, μ^-, r^-). Then, I find within this algebraic scheme a possible place for Higgs scalar and pseudoscalar, both appearing in two replicas. 3 refs. (author)

[en] We study scenarios for chiral symmetry restoration and deconfinement at finite temperature and/or density, based on assuming universal scaling relations for some hadron masses. We explore and discuss consequences of this scaling assumption in nuclear structure and show that most experiments support the scaling. The relevance of soft and hard scales as pertaining to chiral symmetry restoration and deconfinement is emphasized, and scaling relations for nonstrange and strange Goldstone bosons are presented. Theoretical support for the scaling relations is found from the analysis of effective Lagrangians in hot and dense matter, as well as finite-temperature and finite-density QCD sum rules. Both approaches suggest the validity of approximate scaling relations and identify sources of violation of the latter. Finite-temperature hadron masses can be compared to the results of QCD lattice gauge calculations. We show that large screening masses above T_c merging into chiral multiplets are consistent with thermal, rather then dynamically generated, quark masses on the lattice. The results are consistent with vanishing dynamically generated masses above T_c, where T_c is interpreted as the chiral symmetry restoration temperature. We review the ''dynamical confinement'' scenario of hot quarks and show that the hadronic wavefunctions obtained above T_c are consistent with those obtained from recent measurements of the latter in lattice QCD. This suggests that there are strong quark/antiquark correlations in the vector meson channels. We conclude that for finite-temperature QCD, chiral symmetry above T_c is realized in terms of essentially massless multiplets of chiral partners, and that chiral symmetry restoration is the only phase transition. (orig.)

[en] The Green-Kubo-type formulas and the cutoff model motivated by Monte Carlo lattice simulations are applied to find the temperature behavior of the kinetic coefficients for a gluon gas near the phase-transition region. 23 refs

[en] The determination of accurate values of the vector and tensor coupling constants of the vector meson with the nucleon, as in the case of the coupling constant of the photon with the vector meson, is important for many theoretical models of hadronic and nuclear physics. A vector-dominance model (VDM) is traditionally considered as the simplest path to the determination of these constants from the data on electron-proton scattering. The fit of the predicted VDM expressions for the Dirac and Pauli form factors of the nucleon, to the data in the region of low values of the squared 4-momentium transfer, Q²≤1GeV², allows one to estimate with good accuracy the coupling constants. However, in an extended VDM including at least three isoscalar and three isovector mesons, not only the interaction constants, but also the meson masses are usually considered as free parameters of the model. As a consequence of this, the values of the coupling constants essentially depend on the number and masses of the vector mesons

[en] We consider here chiral symmetry breaking through a nontrivial vacuum structure with quark-antiquark condensates. We then relate the condensate function to the wave function of the pion as a Goldstone mode. This simultaneously yields the pion also as a quark-antiquark bound state as a localized zero mode in vacuum. We illustrate the above through the Nambu-Jona-Lasinio model to calculate different pionic properties in terms of the vacuum structure for breaking of exact or approximate chiral symmetry, as well as the condensate fluctuations giving rise to σ mesons

[en] The differential cross-section of the double-charge-exchange (DC X) reaction ¹⁴C(π⁺, π^-) ¹⁴O (g.s.) at 164 MeV is calculated in the hybrid quark hadron (HQH) model. The theoretical results are in good agreement with the experimental data. The short-range effects of DC X reaction come mostly from the six-quark cluster contribution

[en] We review some recent results obtained in the quark meson coupling model. In particular, we discuss the change in the proton electric and magnetic form factors when it is bound in a specific shell model orbit. Modern quasi-elastic electron scattering experiments should be able to detect effects of the size predicted. We also examine the possibility that an ω meson could be bound in a finite nucleus. Copyright (1999) World Scientific Publishing Co. Pte. Ltd