Electromagnetic Form Factors of the Proton in the "Unphysical" Region from gamma p->pe^{+}e^{-} Reaction

Investigation of the proton form factor F-1 (q(2), W-2) in the time-like region 4m(e)(2) <q(2) <4M(2) by measuring the e(+)e(-)-symmetry in the gamma(p,p)e(+)e(-) reaction is proposed. Selection of ''longitudinal'' photons (q(2

Pions in isospin asymmetric matter and nuclear Drell-Yan scattering

Using a self-consistent delta-hole model the pion propagation in isospin asymmetric nuclear matter is studied. In neutron-rich matter, corresponding to heavy nuclei, a significant difference in positive and negative pion light-cone distributions is obtained leading to a nuclear enhancement of up antiquark distribution compared to the down antiquark one. This means that the sea-quark asymmetry in the free nucleon cannot be extracted model independently from an experiment on a neutron-rich nucleus.Comment: 10 pages, 3 figures (included), Latex 2.09, uses elsart.sty, epsf.st

Electromagnetic transitions between giant resonances within a continuum-RPA approach

A general continuum-RPA approach is developed to describe electromagnetic transitions between giant resonances. Using a diagrammatic representation for the three-point Green's function, an expression for the transition amplitude is derived which allows one to incorporate effects of mixing of single and double giant resonances as well as to take the entire basis of particle-hole states into consideration. The radiative widths for E1 transition between the charge-exchange spin-dipole giant resonance and Gamow-Teller states are calculated for ^{90}Nb and ^{208}Bi nuclei. The importance of the mixing is stressed.Comment: 10 pages, 2 figures, uses elsart.st

Production of e+e- pairs in proton-deuteron capture to 3He

The process p+d \leftrightarrow 3He + \gamma* at intermediate energies is described using a covariant and gauge-invariant model, and a realistic pd3He vertex. Both photodisintegration of 3He and proton-deuteron capture with production of e+e- pairs are studied, and results for cross sections and response functions are presented. The effect of time-like formfactors on the dilepton cross sections is investigated as well.Comment: 10 pages, 4 figures, Revtex, to be published in Physics Letters

The Single-Particle Spectral Function of 16O^{16}{\rm O}

The influence of short-range correlations on the $p$-wave single-particle spectral function in $^{16}{\rm O}$ is studied as a function of energy. This influence, which is represented by the admixture of high-momentum components, is found to be small in the $p$-shell quasihole wave functions. It is therefore unlikely that studies of quasihole momentum distributions using the $(e,e'p)$ reaction will reveal a significant contribution of high momentum components. Instead, high-momentum components become increasingly more dominant at higher excitation energy. The above observations are consistent with the energy distribution of high-momentum components in nuclear matter.Comment: 5 pages, RevTeX, 3 figure

Revisiting the Hugenholtz-Van Hove theorem in nuclear matter

An assessment of the magnitude of the rearrangement contribution to the Fermi energy and to the binding energy per particle is carried out in symmetric nuclear matter by extending the G-matrix framework. The restoration of the thermodynamic consistency or, equivalently, the fulfillment of the Hugenholtz-Van Hove theorem, is discussed.Comment: 14 pages, 3 figure

Mean-field analysis of interacting boson models with random interactions

We investigate the origin of the regular features observed in numerical studies of the interacting boson model with random interactions, in particular the dominance of L=0 ground states and the occurrence of vibrational and rotational band structures. It is shown that all of these properties can be interpreted and explained in terms of a Hartree-Bose mean-field analysis, in which different regions of the parameter space are associated with geometric shapes. The same conclusions hold for the vibron model.Comment: 8 pages, 4 figures, 2 tables. Physical Review C, in pres

Improved lower bounds for the ground-state energy of many-body systems

New lower bounds for the binding energy of a quantum-mechanical system of interacting particles are presented. The new bounds are expressed in terms of two-particle quantities and improve the conventional bounds of the Hall-Post type. They are constructed by considering not only the energy in the two-particle system, but also the structure of the pair wave function. We apply the formal results to various numerical examples, and show that in some cases dramatic improvement over the existing bounds is reached.Comment: 29 pages, 5 figures, to be published in Phys. Rev.

Energy Level Statistics of the U(5) and O(6) Symmetries in the Interacting Boson Model

We study the energy level statistics of the states in U(5) and O(6) dynamical symmetries of the interacting boson model and the high spin states with backbending in U(5) symmetry. In the calculations, the degeneracy resulting from the additional quantum number is eliminated manually. The calculated results indicate that the finite boson number $N$ effect is prominent. When $N$ has a value close to a realistic one, increasing the interaction strength of subgroup O(5) makes the statistics vary from Poisson-type to GOE-type and further recover to Poisson-type. However, in the case of $N \to \infty$, they all tend to be Poisson-type. The fluctuation property of the energy levels with backbending in high spin states in U(5) symmetry involves a signal of shape phase transition between spherical vibration and axial rotation.Comment: 38 pages, 13 figure

Pionic contribution to relativistic Fermi Liquid parameters

We calculate pionic contribution to the relativistic Fermi Liquid parameters (RFLPs) using Chiral Effective Lagrangian. The RFLPs so determined are then used to calculate chemical potential, exchange and nuclear symmetry energies due to $\pi$$N$ interaction. We also evaluate two loop ring diagrams involving $\sigma$, $\omega$ and $\pi$ meson exchanges and compare results with what one obtains from the relativistic Fermi Liquid theory (RFLT).Comment: 6 pages, 2 figures, Published in Canadian Journal of Physics, vol. 88, issue 8, pp. 585-59