Giant monopole resonance and nuclear compression modulus for 40Ca and 16O

Using a collective potential derived on the basis of the Generator Coordinate Method with Skyrme interactions we obtain values for the compression modulus of 40Ca which are in good agreement with a recently obtained experimental value. Calculated values for the compression modulus for 16O are also given. The procedure involved in the derivation of the collective potential is briefly reviewed and discussed.Comment: 14 pages, no figures, two tables, REVTE

Innermost Stable Circular Orbits and Epicyclic Frequencies Around a Magnetized Neutron Star

A full-relativistic approach is used to compute the radius of the innermost stable circular orbit (ISCO), the Keplerian, frame-dragging, precession and oscillation frequencies of the radial and vertical motions of neutral test particles orbiting the equatorial plane of a magnetized neutron star. The space-time around the star is modelled by the six parametric solution derived by Pachon et al. It is shown that the inclusion of an intense magnetic field, such as the one of a neutron star, have non-negligible effects on the above physical quantities, and therefore, its inclusion is necessary in order to obtain a more accurate and realistic description of the physical processes occurring in the neighbourhood of this kind of objects such as the dynamics of accretion disk. The results discussed here also suggest that the consideration of strong magnetic fields may introduce non-negligible corrections in, e.g., the relativistic precession model and therefore on the predictions made on the mass of neutron stars.Comment: LaTeX file, 13 pages, 4 figure

Color screening in a constituent quark model of hadronic matter

The effect of color screening on the formation of a heavy quark-antiquark ($Q\bar{Q}$) bound state--such as the $J/\psi$ meson--is studied using a constituent-quark model. The response of the nuclear medium to the addition of two color charges is simulated directly in terms of its quark constituents via a string-flip potential that allows for quark confinement within hadrons yet enables the hadrons to separate without generating unphysical long-range forces. Medium modifications to the properties of the heavy meson, such as its energy and its mean-square radius, are extracted by solving Schr\"odinger's equation for the $Q\bar{Q}$ pair in the presence of a (screened) density-dependent potential. The density dependence of the heavy-quark potential is in qualitative agreement with earlier studies of its temperature dependence extracted from lattice calculations at finite temperature. In the present model it is confirmed that abrupt changes in the properties of the $J/\psi$-meson in the hadronic medium ({\it plasma}), correlate strongly with the deconfining phase transition.Comment: 7 pages, 3 figures, submitted to PRC for publication, uses revtex