1,075 research outputs found
Approximate particle number projection with density dependent forces: Superdeformed bands in the A=150 and A=190 regions
We derive the equations for approximate particle number projection based on
mean field wave functions with finite range density dependent forces. As an
application ground bands of even-A superdeformed nuclei in the A=150 and A=190
regions are calculated with the Gogny force.
We discuss nuclear properties such as quadrupole moments, moments of inertia
and quasiparticle spectra, among others, as a function of the angular momentum.
We obtain a good overall description.Comment: 31 pages, 10 figures, 3 appendices. In press in Nucl. Phy
Angular momentum projected analysis of Quadrupole Collectivity in \protect(^{30,32,34}Mg\protect) and \protect(^{32,34,36,38}Si\protect) with the Gogny interaction
A microscopic angular momentum projection after variation is used to describe
quadrupole collectivity in (^{30,32,34}Mg) and (^{32,34,36,38}Si). The
Hartree-Fock-Bogoliubov states obtained in the quadrupole constrained mean
field approach are taken as intrinsic states for the projection. Excitation
energies of the first (2^{+}) states and the (B(E2,0^{+}\to 2^{+})) transition
probabilities are given. A reasonable agreement with available experimental
data is obtained. It is also shown that the mean field picture of those nuclei
is strongly modified by the projection.Comment: 10 pages, 2 figures, to be published in Phys. Lett.
Particle number projection with effective forces
The particle number projection method is formulated for density dependent
forces and in particular for the finite range Gogny force. Detailed formula for
the projected energy and its gradient are provided. The problems arising from
the neglection of any exchange term, which may lead to divergences, are
throughly discussed and the possible inaccuracies estimated. Numericala results
for the projection after variation method are shown for the nucleus 164Er and
for the projection before variation approach for the nuclei 48-50Cr. We also
confirm the Coulomb antipairing effect found in mean field theories.Comment: 33 pages, 8 figures. Submit to Nuc. Phys.
Reheating Temperature and Gauge Mediation Models of Supersymmetry Breaking
For supersymmetric theories with gravitino dark matter, the maximal reheating
temperature consistent with big bang nucleosynthesis bounds arises when the
physical gaugino masses are degenerate. We consider the cases of a stau or
sneutrino next-to-lightest superpartner, which have relatively less constraint
from big bang nucleosynthesis. The resulting parameter space is consistent with
leptogenesis requirements, and can be reached in generalized gauge mediation
models. Such models illustrate a class of theories that overcome the well-known
tension between big bang nucleosynthesis and leptogenesis.Comment: 30 pages, 4 figures; v2: refs adde
Mass formulas and thermodynamic treatment in the mass-density-dependent model of strange quark matter
The previous treatments for strange quark matter in the quark
mass-density-dependent model have unreasonable vacuum limits. We provide a
method to obtain the quark mass parametrizations and give a self-consistent
thermodynamic treatment which includes the MIT bag model as an extreme. In this
treatment, strange quark matter in bulk still has the possibility of absolute
stability. However, the lower density behavior of the sound velocity is
opposite to previous findings.Comment: Formatted in REVTeX 3.1, 5 pages, 3 figures, to appear in PRC6
Ballistic electron transport through magnetic domain walls
Electron transport limited by the rotating exchange-potential of domain walls
is calculated in the ballistic limit for the itinerant ferromagnets Fe, Co, and
Ni. When realistic band structures are used, the domain wall magnetoresistance
is enhanced by orders of magnitude compared to the results for previously
studied two-band models. Increasing the pitch of a domain wall by confinement
in a nano-structured point contact is predicted to give rise to a strongly
enhanced magnetoresistance.Comment: 4 pages, 2 figures; to appear in PRB as a brief repor
Strong Final State Interactions in gamma.gamma --> W+W-
We study the effects of a possible strong final state interaction among
longitudinal W's in gamma.gamma --> W+W-. The relevant partial wave amplitudes
are modified by an Omn\`es function approximated by a Breit-Wigner form factor.
We study the fractional cross section f_{00} = \sigma_{LL}/\sigma_{Total} with
both W's longitudinally polarised, in the presence of a J = 2 resonance (M =
2.5 TeV, Width = 500 GeV) or a J = 0 resonance (M = 1 TeV, Width = 1 TeV),
whose parameters are scaled up from the f_2 and \sigma resonances in the \pi\pi
system. We also examine the effects of final state interaction in the case of
polarised photons (J_z = 0 or J_z = 2), and the impact on the
Drell-Hearn-Gerasimov sum rule.Comment: 12 pages including figure
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