Quark-Meson Coupling Model for a Nucleon

The quark-meson coupling model for a nucleon is considered. The model describes a nucleon as an MIT bag, in which quarks are coupled to scalar and vector mesons. A set of coupled equations for the quark and the meson fields are obtained and are solved in a self-consistent way. It is shown that the mass of a nucleon as a dressed MIT bag interacting with sigma- and omega-meson fields significantly differs from the mass of a free MIT bag. A few sets of model parameters are obtained so that the mass of a dressed MIT bag becomes the nucleon mass. The results of our calculations imply that the self-energy of the bag in the quark-meson coupling model is significant and needs to be considered in doing the nuclear matter calculations.Comment: 3 figure

Charge Symmetry Violation in Nuclear Physics

The study of charge symmetry violation in nuclear physics is a potentially enormous subject. Through a few topical examples we aim to show that it is not a subject of peripheral interest but rather goes to the heart of our understanding of hadronic systems.Comment: Invited talk at the Int. Conference on Weak and Electromagnetic Interactions in Nuclei, Osaka, June 12-16 199

Effect of nucleon structure variation on the longitudinal response function

Using the quark-meson coupling (QMC) model, we study the longitudinal response function for quasielastic electron scattering from nuclear matter. In QMC the coupling constant between the scalar ($\sigma$) meson and the nucleon is expected to decrease with increasing nuclear density, because of the self-consistent modification of the structure of the nucleon. The reduction of the coupling constant then leads to a smaller contribution from relativistic RPA than in the Walecka model. However, since the electromagnetic form factors of the in-medium nucleon are modified at the same time, the longitudinal response function and the Coulomb sum are reduced by a total of about 20% in comparison with the Hartree contribution. We find that the relativistic RPA and the nucleon structure variation both contribute about fifty-fifty to the reduction of the longitudinal response.Comment: 14 pages, including 3 ps file

Charge symmetry breaking in mirror nuclei from quarks

The binding energy differences of the valence proton and neutron of the mirror nuclei, $^{15}$O -- $^{15}$N, $^{17}$F -- $^{17}$O, $^{39}$Ca -- $^{39}$K and $^{41}$Sc -- $^{41}$Ca, are calculated using the quark-meson coupling (QMC) model. The calculation involves nuclear structure and shell effects explicitly. It is shown that binding energy differences of a few hundred keV arise from the strong interaction, even after subtracting all electromagnetic corrections. The origin of these differences may be ascribed to the charge symmetry breaking effects set in the strong interaction through the u and d current quark mass difference.Comment: Revtex (preprint style), 11 pages, 2 postscript figures. The number of parameters has been reduced. (The d current quark mass is also calculated in the model.) Numerical results and figures revised. Version to appear in Phys. Lett.

A canonical Frobenius structure

We show that it makes sense to speak of THE Frobenius manifold attached to a convenient and nondegenerate Laurent polynomialComment: 24 page

Two-scale scalar mesons in nuclei

We generalize the linear sigma model in order to develop a chiral-invariant model of nuclear structure. The model is natural, and contains not only the usual sigma meson which is the chiral partner of the pion but also a new chiral-singlet that is responsible for the medium-range nucleon-nucleon attraction. This approach provides significant advantages in terms of its description of nuclear matter and finite nuclei in comparison with conventional models based on the linear sigma model.Comment: 12 pages, including 3 tables and 3 figures; preprint number is adde

Self-consistent quantum effects in the quark meson coupling model

We derive the equation of state of nuclear matter including vacuum polarization effects arising from the nucleons and the sigma mesons in the quark-meson coupling model which incorporates explicitly quark degrees of freedom with quark coupled to the scalar and vector mesons. This leads to a softer equation of state for nuclear matter giving a lower value of incompressibility than would be reached without quantum effects. The {\it in-medium} nucleon and sigma meson masses are also calculated in a self-consistent manner.Comment: 10 pages, latex, 5 figure

Quarks in Finite Nuclei

We describe the development of a theoretical description of the structure of finite nuclei based on a relativistic quark model of the structure of the bound nucleons which interact through the (self-consistent) exchange of scalar and vector mesons.Comment: Invited talks presented at the Joint Japan-Australian Workshop on "Quarks, Hadrons and Nuclei", Adelaide, November 1995, to appear in Australian Jounal of Physic