Variational Methods for Nuclear Systems with Dynamical Mesons

We derive a model Hamiltonian whose ground state expectation value of any two-body operator coincides with that obtained with the Jastrow correlated wave function of the many-body Fermi system. Using this Hamiltonian we show that the variational principle can be extended to treat systems with dynamical mesons, even if in this case the concept of wave function looses its meaning

Computational spectroscopy of helium-solvated molecules: effective inertia, from small He clusters toward the nano-droplet regime

Accurate computer simulations of the rotational dynamics of linear molecules solvated in He clusters indicate that the large-size (nano-droplet) regime is attained quickly for light rotors (HCN, CO) and slowly for heavy ones (OCS, N$_2$O, CO$_2$), thus challenging previously reported results. Those results spurred the view that the different behavior of light rotors with respect to heavy ones - including a smaller reduction of inertia upon solvation of the former - would result from the lack of adiabatic following of the He density upon molecular rotation. We have performed computer experiments in which the rotational dynamics of OCS and HCN molecules was simulated using a fictitious inertia appropriate to the other molecule. These experiments indicate that the approach to the nano-droplet regime, as well as the reduction of the molecular inertia upon solvation, is determined by the anistropy of the potential, more than by the molecular weight. Our findings are in agreement with recent infrared and/or microwave experimental data which, however, are not yet totally conclusive by themselves.Comment: 11 pages, 13 figure

Quark-Hadron Duality in Structure Functions

Quark-hadron duality is studied in a systematic way for both the unpolarized and polarized structure functions, by taking into account all the available data in the resonance region.In both cases, a detailed perturbative QCD based analysis of the structure functions integrals in the resonance region is performed: non perturbative contributions are disentangled, and higher twist terms are evaluated. A different behavior between the unpolarized and polarized structure functions at low Q^2 is found.Comment: 5 pages, 4 figure

A Perturbative QCD Based Study of Polarized Nucleon Structure in the Transition Region and Beyond: "Quarks, Color Neutral Clusters, and Hadrons"

A large fraction of the world data on both polarized and unpolarized inclusive $ep$ scattering at large Bjorken $x$ lies in the resonance region where a correspondence with the deep inelastic regime, known as Bloom and Gilman's duality, was observed. Recent analyses of the $Q^2$ dependence of the data show that parton-hadron duality is inconsistent with the twist expansion at low values of the final state invariant mass. We investigate the nature of this disagreement, and we interpret its occurrence in terms of contributions from non partonic degrees of freedom in a preconfinement model.Comment: 5 pages, 1 figure, to be published in the Proceedings of the "3rd International Symposium on the Gerasimov-Drell-Hearn Sum Rule and its Extensions", Editors, J.P. Chen and S. Kuh

Phase oscillations in superfluid 3He-B weak links

Oscillations in quantum phase about a mean value of $\pi$, observed across micropores connecting two \helium baths, are explained in a Ginzburg-Landau phenomenology. The dynamics arises from the Josephson phase relation,the interbath continuity equation, and helium boundary conditions. The pores are shown to act as Josephson tunnel junctions, and the dynamic variables are the inter bath phase difference and fractional difference in superfluid density at micropores. The system maps onto a non-rigid, momentum-shortened pendulum, with inverted-orientation oscillations about a vertical tilt angle $\phi = \pi$, and other modes are predicted

On the behaviour of the nuclear spectral function at high momentum and removal energy

The extrapolation of the nuclear spectral function at large nucleon three-momentum and removal energy is suggested.Comment: 13 pages, 2 Postscript figure

Quantum Monte Carlo Algorithm Based on Two-Body Density Functional Theory for Fermionic Many-Body Systems: Application to 3He

We construct a quantum Monte Carlo algorithm for interacting fermions using the two-body density as the fundamental quantity. The central idea is mapping the interacting fermionic system onto an auxiliary system of interacting bosons. The correction term is approximated using correlated wave functions for the interacting system, resulting in an effective potential that represents the nodal surface. We calculate the properties of 3He and find good agreement with experiment and with other theoretical work. In particular, our results for the total energy agree well with other calculations where the same approximations were implemented but the standard quantum Monte Carlo algorithm was usedComment: 4 pages, 3 figures, 1 tabl