208 research outputs found
Antisymmetrized Green's function approach to reactions with a realistic nuclear density
A completely antisymmetrized Green's function approach to the inclusive
quasielastic scattering, including a realistic one-body density, is
presented. The single particle Green's function is expanded in terms of the
eigenfunctions of the nonhermitian optical potential. This allows one to treat
final state interactions consistently in the inclusive and in the exclusive
reactions. Nuclear correlations are included in the one-body density. Numerical
results for the response functions of O and Ca are presented and
discussed.Comment: 45 pages, 3 figure
Toward a Global Dispersive Optical Model for the Driplines
A dispersive-optical-model analysis has been performed for both protons and
neutrons on 40,42,44,48Ca isotopes. The fitted potentials describe accurately
both scattering and bound quantities and extrapolate well to other stable
nuclei.
Further experimental information will be gathered to constrain extrapolations
toward the driplines.Comment: Invited talk at the "10th International Conference on Nucleus-Nucleus
Collisions", Beijing, 16-21 August 200
Shortcuts to adiabaticity for trapped ultracold gases
We study, experimentally and theoretically, the controlled transfer of
harmonically trapped ultracold gases between different quantum states. In
particular we experimentally demonstrate a fast decompression and displacement
of both a non-interacting gas and an interacting Bose-Einstein condensate which
are initially at equilibrium. The decompression parameters are engineered such
that the final state is identical to that obtained after a perfectly adiabatic
transformation despite the fact that the fast decompression is performed in the
strongly non-adiabatic regime. During the transfer the atomic sample goes
through strongly out-of-equilibrium states while the external confinement is
modified until the system reaches the desired stationary state. The scheme is
theoretically based on the invariants of motion and scaling equations
techniques and can be generalized to decompression trajectories including an
arbitrary deformation of the trap. It is also directly applicable to arbitrary
initial non-equilibrium states.Comment: 36 pages, 14 figure
Ground-state densities and pair correlation functions in parabolic quantum dots
We present an extensive comparative study of ground-state densities and pair
distribution functions for electrons confined in two-dimensional parabolic
quantum dots over a broad range of coupling strength and electron number. We
first use spin-density-functional theory to determine spin densities that are
compared with Diffusion Monte Carlo (DMC) data. This accurate knowledge of
one-body properties is then used to construct and test a local approximation
for the electron-pair correlations. We find very satisfactory agreement between
this local scheme and the available DMC data, and provide a detailed picture of
two-body correlations in a coupling-strength regime preceding the formation of
Wigner-like electron ordering.Comment: 18 pages, 12 figures, submitte
Analysis of exchange terms in a projected ERPA Theory applied to the quasi-elastic (e,e') reaction
A systematic study of the influence of exchange terms in the longitudinal and
transverse nuclear response to quasi-elastic (e,e') reactions is presented. The
study is performed within the framework of the extended random phase
approximation (ERPA), which in conjuction with a projection method permits a
separation of various contributions tied to different physical processes. The
calculations are performed in nuclear matter up to second order in the residual
interaction for which we take a (pi+rho)-model with the addition of the
Landau-Migdal g'-parameter. Exchange terms are found to be important only for
the RPA-type contributions around the quasielastic peak.Comment: 29 pages, 6 figs (3 in postscript, 3 faxed on request), epsf.st
Many-body effects in 16O(e,e'p)
Effects of nucleon-nucleon correlations on exclusive reactions on
closed-shell nuclei leading to single-hole states are studied using
( MeV, ) as an example. The quasi-hole wave
function, calculated from the overlap of translationally invariant many-body
variational wave functions containing realistic spatial, spin and isospin
correlations, seems to describe the initial state of the struck proton
accurately inside the nucleus, however it is too large at the surface. The
effect of short-range correlations on the final state is found to be largely
cancelled by the increase in the transparency for the struck proton. It is
estimated that the values of the spectroscopic factors obtained with the DWIA
may increase by a few percent due to correlation effects in the final state.Comment: 21 Pages, PHY-7849-TH-9
Quasiparticle spectrum and dynamical stability of an atomic Bose-Einstein condensate coupled to a degenerate Fermi gas
The quasiparticle excitations and dynamical stability of an atomic
Bose-Einstein condensate coupled to a quantum degenerate Fermi gas of atoms at
zero temperature is studied. The Fermi gas is assumed to be either in the
normal state or to have undergone a phase transition to a superfluid state by
forming Cooper pairs. The quasiparticle excitations of the Bose-Einstein
condensate exhibit a dynamical instability due to a resonant exchange of energy
and momentum with quasiparticle excitations of the Fermi gas. The stability
regime for the bosons depends on whether the Fermi gas is in the normal state
or in the superfluid state. We show that the energy gap in the quasiparticle
spectrum for the superfluid state stabilizes the low energy energy excitations
of the condensate. In the stable regime, we calculate the boson quasiparticle
spectrum, which is modified by the fluctuations in the density of the Fermi
gas.Comment: 12 pages, 3 figure
QSAR models of human data can enrich or replace LLNA testing for human skin sensitization
An example of structural transformation of human skin sensitizers into various non-sensitizers based on interpretation of QSAR models
Double-well magnetic trap for Bose-Einstein condensates
We present a magnetic trapping scheme for neutral atoms based on a hybrid of
Ioffe-Pritchard and Time-averaged Orbiting Potential traps. The resulting
double-well magnetic potential has readily controllable barrier height and well
separation. This offers a new tool for studying the behavior of Bose
condensates in double-well potentials, including atom interferometry and
Josephson tunneling. We formulate a description for the potential of this
magnetic trap and discuss practical issues such as loading with atoms,
evaporative cooling and manipulating the potential.Comment: 7 pages, 6 figures, Revtex
Self-consistent Green's function approaches
We present the fundamental techniques and working equations of many-body
Green's function theory for calculating ground state properties and the
spectral strength. Green's function methods closely relate to other polynomial
scaling approaches discussed in chapters 8 and 10. However, here we aim
directly at a global view of the many-fermion structure. We derive the working
equations for calculating many-body propagators, using both the Algebraic
Diagrammatic Construction technique and the self-consistent formalism at finite
temperature. Their implementation is discussed, as well as the inclusion of
three-nucleon interactions. The self-consistency feature is essential to
guarantee thermodynamic consistency. The pairing and neutron matter models
introduced in previous chapters are solved and compared with the other methods
in this book.Comment: 58 pages, 14 figures, Submitted to Lect. Notes Phys., "An advanced
course in computational nuclear physics: Bridging the scales from quarks to
neutron stars", M. Hjorth-Jensen, M. P. Lombardo, U. van Kolck, Editor
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