3,336 research outputs found
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,
NO, CO), 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 scattering at large Bjorken 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 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 , 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 , 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
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