21,987 research outputs found
Generalized MICZ-Kepler Problems and Unitary Highest Weight Modules
For each integer , we demonstrate that a -dimensional
generalized MICZ-Kepler problem has an \mr{Spin}(2, 2n+2) dynamical symmetry
which extends the manifest \mr{Spin}(2n+1) symmetry. The Hilbert space of
bound states is shown to form a unitary highest weight \mr{Spin}(2,
2n+2)-module which occurs at the first reduction point in the
Enright-Howe-Wallach classification diagram for the unitary highest weight
modules. As a byproduct, we get a simple geometric realization for such a
unitary highest weight \mr{Spin}(2, 2n+2)-module.Comment: 27 pages, Refs. update
Self-gravitating Yang Monopoles in all Dimensions
The (2k+2)-dimensional Einstein-Yang-Mills equations for gauge group SO(2k)
(or SU(2) for k=2 and SU(3) for k=3) are shown to admit a family of
spherically-symmetric magnetic monopole solutions, for both zero and non-zero
cosmological constant Lambda, characterized by a mass m and a magnetic-type
charge. The k=1 case is the Reissner-Nordstrom black hole. The k=2 case yields
a family of self-gravitating Yang monopoles. The asymptotic spacetime is
Minkowski for Lambda=0 and anti-de Sitter for Lambda<0, but the total energy is
infinite for k>1. In all cases, there is an event horizon when m>m_c, for some
critical mass , which is negative for k>1. The horizon is degenerate when
m=m_c, and the near-horizon solution is then an adS_2 x S^{2k} vacuum.Comment: 16 pp. Extensive revision to include case of non-zero cosmological
constant and implications for adS/CFT. Numerous additional reference
Reflection asymmetric relativistic mean field approach and its application to the octupole deformed nucleus Ra
A Reflection ASymmetric Relativistic Mean Field (RAS-RMF) approach is
developed by expanding the equations of motion for both the nucleons and the
mesons on the eigenfunctions of the two-center harmonic-oscillator potential.
The efficiency and reliability of the RAS-RMF approach are demonstrated in its
application to the well-known octupole deformed nucleus Ra and the
available data, including the binding energy and the deformation parameters,
are well reproduced.Comment: 4 pages, 2 figures, and 2 tables, to appear in Chinese Physics
Letter
Particles in classically forbidden area, neutron skin and halo, and pure neutron matter in Ca isotopes
The nucleon density distributions and the thickness of pure neutron matter in
Ca isotopes were systematically studied using the Skyrme-Hartree-Fock model
(SHF) from the -stability line to the neutron drip-line. The pure
neutron matter, related with the neutron skin or halo, was shown to depend not
only on the Fermi levels of the neutrons but also on the orbital angular
momentum of the valence neutrons. New definitions for the thickness of pure
neutron matter are proposed.Comment: 6 pages, 5 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
Spurious Shell Closures in the Relativistic Mean Field Model
Following a systematic theoretical study of the ground-state properties of
over 7000 nuclei from the proton drip line to the neutron drip line in the
relativistic mean field model [Prog. Theor. Phys. 113 (2005) 785], which is in
fair agreement with existing experimental data, we observe a few spurious shell
closures, i.e. proton shell closures at Z=58 and Z=92. These spurious shell
closures are found to persist in all the effective forces of the relativistic
mean field model, e.g. TMA, NL3, PKDD and DD-ME2.Comment: 3 pages, to appear in Chinese Physics Letter
Composition dependence of electronic structure and optical properties of Hf1-xSixOy gate dielectrics
Copyright © 2008 American Institute of Physics. This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditionsComposition-dependent electronic structure and optical properties of Hf1âxSixOy 0.1 x 0.6 gate
dielectrics on Si at 450 °C grown by UV-photo-induced chemical vapor deposition UV-CVD have
been investigated via x-ray photoemission spectroscopy and spectroscopy ellipsometry SE . By
means of the chemical shifts in the Hf 4f, Si 2p, and O 1s spectra, the HfâOâSi bondings in the
as-deposited films have been confirmed. Analyses of composition-dependent band alignment of
Hf1âxSixOy / Si gate stacks have shown that the valence band VB offset Ev demonstrates little
change; however, the values of conduction band offset Ec increase with the increase in the silicon
atomic composition, resulting from the increase in the separation between oxygen 2p orbital VB
state and antibonding d states intermixed of Hf and Si. Analysis by SE, based on the TaucâLorentz
model, has indicated that decreases in the optical dielectric constant and increase in band gap have
been observed as a function of silicon contents. Changes in the complex dielectric functions and
band gap Eg related to the silicon concentration in the films are discussed systematically. From the
band offset and band gap viewpoint, these results suggest that Hf1âxSixOy films provide sufficient
tunneling barriers for electrons and holes, making them promising candidates as alternative gate
dielectrics.National Natural Science Foundation of China and Royal Society U.K
Superfluidity in a Three-flavor Fermi Gas with SU(3) Symmetry
We investigate the superfluidity and the associated Nambu-Goldstone modes in
a three-flavor atomic Fermi gas with SU(3) global symmetry. The s-wave pairing
occurs in flavor anti-triplet channel due to the Pauli principle, and the
superfluid state contains both gapped and gapless fermionic excitations.
Corresponding to the spontaneous breaking of the SU(3) symmetry to a SU(2)
symmetry with five broken generators, there are only three Nambu-Goldstone
modes, one is with linear dispersion law and two are with quadratic dispersion
law. The other two expected Nambu-Goldstone modes become massive with a mass
gap of the order of the fermion energy gap in a wide coupling range. The
abnormal number of Nambu-Goldstone modes, the quadratic dispersion law and the
mass gap have significant effect on the low temperature thermodynamics of the
matter.Comment: 9 pages, 2 figures, published versio
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