603 research outputs found
Interaction of Ultra-Cold Neutrons with Condensed Matter
General theory of neutron scattering (elastic and inelastic) is presented. It
is applicable for the whole domain of slow neutrons and includes as limiting
cases existing theories for thermal and cold neutrons and for elastic
scattering of UCN. New expression for inelastic scattering cross section for
UCN is proposed. It differs from the usually used by proper account of
re-scattering processes. Evidence for small heating and cooling of UCN is
given.Comment: 9 pages, 1 figure included, latex, report at workshop "Particle
Physics with Slow Neutrons" (Octorber 1998, Grenoble, France), to be
published in the Workshop Proceeding
High-Temperature Properties of the Z(3) Interface in (2+1)-D SU(3) Gauge Theory
We study the high-temperature properties of the Z(3) interface which forms
between the various ordered phases of pure SU(3) gauge theory above a critical
temperature. On a (2+1)-D Euclidean lattice, we perform an accurate measurement
of the interface tension, which shows good agreement with the prediction of
perturbation theory. We also examine the behaviour of the Debye electric
screening mass, and compare this with theoretical predictions.Comment: 10 pages, 3 figures, uuencoded gzipped tar fil
Interplay of pairing and multipole interactions in a simple model
The interplay of pairing and other interactions is addressed in this work
using a simple single-j model. We show that enhancements in pairing
correlations observed through studies of the spectra of deformed systems,
moments of inertia, changes in transitional multipole amplitudes, and direct
calculations of the pairing component in the wave function, indicate that even
without explicit matrix elements responsible for pairing, a paired state can
still appear from the kinematic coupling of pairing to deformation and from
other geometrical restrictions that are of extreme importance in mesoscopic
systems. Furthermore, we demonstrate that macroscopic transitions such as
oblate to prolate shape changes can lead to strong dynamic enhancements of
pairing correlations. In this work we emphasize that the pairing condensate has
an important dynamic and kinematic effect on other residual interactions.Comment: 39 pages, 8 figure
Shape and blocking effects on odd-even mass differences and rotational motion of nuclei
Nuclear shapes and odd-nucleon blockings strongly influence the odd-even
differences of nuclear masses. When such effects are taken into account, the
determination of the pairing strength is modified resulting in larger pair
gaps. The modified pairing strength leads to an improved self-consistent
description of moments of inertia and backbending frequencies, with no
additional parameters.Comment: 7 pages, 3 figures, subm to PR
Approximate Particle Number Projection for Rotating Nuclei
Pairing correlations in rotating nuclei are discussed within the
Lipkin-Nogami method. The accuracy of the method is tested for the
Krumlinde-Szyma\'nski R(5) model. The results of calculations are compared with
those obtained from the standard mean field theory and particle-number
projection method, and with exact solutions.Comment: 15 pages, 6 figures available on request, REVTEX3.
Interaction of the single-particle and collective degrees of freedom in non-magic nuclei: the role of phonon tadpole terms
A method of a consistent consideration of the phonon contributions to mass
and gap operators in non-magic nuclei is developed in the so-called g^2
approximation, where g is the low-lying phonon creation amplitude. It includes
simultaneous accounting for both the usual non-local terms and the phonon
tadpole ones. The relations which allow the tadpoles to be calculated without
any new parameters are derived. As an application of the results, the role of
the phonon tadpoles in the single-particle strength distribution and in the
single-particle energies and gap values has been considered. Relation to the
problem of the surface nature of pairing is discussed.Comment: 22 pages, 7 figure
Spherical Relativistic Hartree theory in a Woods-Saxon basis
The Woods-Saxon basis has been suggested to replace the widely used harmonic
oscillator basis for solving the relativistic mean field (RMF) theory in order
to generalize it to study exotic nuclei. As examples, relativistic Hartree
theory is solved for spherical nuclei in a Woods-Saxon basis obtained by
solving either the Schr\"odinger equation or the Dirac equation (labelled as
SRHSWS and SRHDWS, respectively and SRHWS for both). In SRHDWS, the negative
levels in the Dirac Sea must be properly included. The basis in SRHDWS could be
smaller than that in SRHSWS which will simplify the deformed problem. The
results from SRHWS are compared in detail with those from solving the spherical
relativistic Hartree theory in the harmonic oscillator basis (SRHHO) and those
in the coordinate space (SRHR). All of these approaches give identical nuclear
properties such as total binding energies and root mean square radii for stable
nuclei. For exotic nuclei, e.g., Ca, SRHWS satisfactorily reproduces the
neutron density distribution from SRHR, while SRHHO fails. It is shown that the
Woods-Saxon basis can be extended to more complicated situations for exotic
nuclei where both deformation and pairing have to be taken into account.Comment: 12 pages, 9 figure
Quantum Corrections to Dilute Bose Liquids
It was recently shown (A. Bulgac. Phys. Rev. Lett. {\bf 89}, 050402 (2002))
that an entirely new class of quantum liquids with widely tunable properties
could be manufactured from bosons (boselets), fermions (fermilets) and their
mixtures (ferbolets) by controlling their interaction properties by the means
of a Feshbach resonance. We extend the previous mean--field analysis of these
quantum liquids by computing the lowest order quantum corrections to the ground
state energy and the depletion of the Bose--Einstein condensate and by
estimating higher order corrections as well. We show that the quantum
corrections are relatively small and controlled by the diluteness parameter
, even though strictly speaking in this case there is no
low density expansion.Comment: final published version, typos corrected, updated references and
added one referenc
Low-lying quadrupole collective states of the light and medium Xenon isotopes
Collective low lying levels of light and medium Xenon isotopes are deduced
from the Generalized Bohr Hamiltonian (GBH). The microscopic seven functions
entering into the GBH are built from a deformed mean field of the Woods-Saxon
type. Theoretical spectra are found to be close to the ones of the experimental
data taking into account that the calculations are completely microscopic, that
is to say, without any fitting of parameters.Comment: 8 pages, 4 figures, 1 tabl
Mean-field description of ground-state properties of drip-line nuclei. (I) Shell-correction method
A shell-correction method is applied to nuclei far from the beta stability
line and its suitability to describe effects of the particle continuum is
discussed. The sensitivity of predicted locations of one- and two-particle drip
lines to details of the macroscopic-microscopic model is analyzed.Comment: 22 REVTeX pages, 13 uuencoded postscript figures available upon
reques
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