781 research outputs found
Star product formula of theta functions
As a noncommutative generalization of the addition formula of theta
functions, we construct a class of theta functions which are closed with
respect to the Moyal star product of a fixed noncommutative parameter. These
theta functions can be regarded as bases of the space of holomorphic
homomorphisms between holomorphic line bundles over noncommutative complex
tori.Comment: 12 page
Recurrent dynamical symmetry breaking and restoration by Wilson lines at finite densities on a torus
In this paper we derive the general expression of a one-loop effective
potential of the nonintegrable phases of Wilson lines for an SU(N) gauge theory
with a massless adjoint fermion defined on the spactime manifold
at finite temperature and fermion density. The Phase
structure of the vacuum is presented for the case with and N=2 at zero
temperature. It is found that gauge symmetry is broken and restored alternately
as the fermion density increases, a feature not found in the Higgs mechanism.
It is the manifestation of the quantum effects of the nonintegrable phases.Comment: 17 pages, 2 figure
Finding Faint Intermediate-mass Black Holes in the Radio Band
We discuss the prospects for detecting faint intermediate-mass black holes,
such as those predicted to exist in the cores of globular clusters and dwarf
spheroidal galaxies. We briefly summarize the difficulties of stellar dynamical
searches, then show that recently discovered relations between black hole mass,
X-ray luminosity and radio luminosity imply that in most cases, these black
holes should be more easily detected in the radio than in the X-rays. Finally,
we show upper limits from some radio observations of globular clusters, and
discuss the possibility that the radio source in the core of the Ursa Minor
dwarf spheroidal galaxy might be a black hole.Comment: 10 pages, no figures, to appear in From X-ray Binaries to Quasars:
Black Hole Accretion on All Mass Scales, ed. T. J. Maccarone, R. P. Fender,
and L. C. Ho (Dordrecht: Kluwer
Spectrum of the Vortex Bound States of the Dirac and Schrodinger Hamiltonian in the presence of Superconducting Gaps
We investigate the vortex bound states both Schrodinger and Dirac Hamiltonian
with the s-wave superconducting pairing gap by solving the mean-field
Bogoliubov-de-Gennes equations. The exact vortex bound states spectrum is
numerically determined by the integration method, and also accompanied by the
quasi-classical analysis. It is found that the bound state energies is
proportional to the vortex angular momentum when the chemical potential is
large enough. By applying the external magnetic field, the vortex bound state
energies of the Dirac Hamiltonian are almost unchanged; whereas the energy
shift of the Schrodinger Hamiltonian is proportional to the magnetic field.
These qualitative differences may serve as an indirect evidence of the
existence of Majorana fermions in which the zero mode exists in the case of the
Dirac Hamiltonian only.Comment: 8 pages, 9 figure
Ferromagnetic phase transition and Bose-Einstein condensation in spinor Bose gases
Phase transitions in spinor Bose gases with ferromagnetic (FM) couplings are
studied via mean-field theory. We show that an infinitesimal value of the
coupling can induce a FM phase transition at a finite temperature always above
the critical temperature of Bose-Einstein condensation. This contrasts sharply
with the case of Fermi gases, in which the Stoner coupling can not lead
to a FM phase transition unless it is larger than a threshold value . The
FM coupling also increases the critical temperatures of both the ferromagnetic
transition and the Bose-Einstein condensation.Comment: 4 pages, 4 figure
The Electric Dipole Moment of the Nucleons in Holographic QCD
We introduce the strong CP-violation in the framework of AdS/QCD model and
calculate the electric dipole moments of nucleons as well as the CP-violating
pion-nucleon coupling. Our holographic estimate of the electric dipole moments
gives for the neutron d_n=1.08 X 10^{-16} theta (e cm), which is comparable
with previous estimates. We also predict that the electric dipole moment of the
proton should be precisely the minus of the neutron electric dipole moment,
thus leading to a new sum rule on the electric dipole moments of baryons.Comment: 22 pages, no figures. v2: A reference and an acknowledgment added.
v3: One more reference, to appear in JHE
Entangled quantum tunneling of two-component Bose-Einstein condensates
We examine the quantum tunneling process in Bose condensates of two
interacting species trapped in a double well configuration. We discover the
condition under which particles of different species can tunnel as pairs
through the potential barrier between two wells in opposition directions. This
novel form of tunneling is due to the interspecies interaction that eliminates
the self- trapping effect. The correlated motion of tunneling atoms leads to
the generation of quantum entanglement between two macroscopically coherent
systems.Comment: 4 pages, 3 figure
Quantum Computing with Atomic Josephson Junction Arrays
We present a quantum computing scheme with atomic Josephson junction arrays.
The system consists of a small number of atoms with three internal states and
trapped in a far-off resonant optical lattice. Raman lasers provide the
"Josephson" tunneling, and the collision interaction between atoms represent
the "capacitive" couplings between the modes. The qubit states are collective
states of the atoms with opposite persistent currents. This system is closely
analogous to the superconducting flux qubit. Single qubit quantum logic gates
are performed by modulating the Raman couplings, while two-qubit gates result
from a tunnel coupling between neighboring wells. Readout is achieved by tuning
the Raman coupling adiabatically between the Josephson regime to the Rabi
regime, followed by a detection of atoms in internal electronic states.
Decoherence mechanisms are studied in detail promising a high ratio between the
decoherence time and the gate operation time.Comment: 7 figure
Reversed anisotropies and thermal contraction of FCC (110) surfaces
The observed anisotropies of surface vibrations for unreconstructed FCC metal
(110) surfaces are often reversed from the "common sense" expectation. The
source of these reversals is investigated by performing ab initio density
functional theory calculations to obtain the surface force constant tensors for
Ag(110), Cu(110) and Al(110). The most striking result is a large enhancement
in the coupling between the first and third layers of the relaxed surface,
which strongly reduces the amplitude of out-of-plane vibrations of atoms in the
first layer. This also provides a simple explanation for the thermal
contraction of interlayer distances. Both the anisotropies and the thermal
contraction arise primarily as a result of the bond topology, with all three
(110) surfaces showing similar behavior.Comment: 13 pages, in revtex format, plus 1 postscript figur
Active Galaxies in the UV
In this article we present different aspects of AGN studies demonstrating the
importance of the UV spectral range. Most important diagnostic lines for
studying the general physical conditions as well as the metalicities in the
central broad line region in AGN are emitted in the UV. The UV/FUV continuum in
AGN excites not only the emission lines in the immediate surrounding but it is
responsible for the ionization of the intergalactic medium in the early stages
of the universe. Variability studies of the emission line profiles of AGN in
the UV give us information on the structure and kinematics of the immediate
surrounding of the central supermassive black hole as well as on its mass
itself.Comment: 29 pages, 13 figures, Ap&SS in pres
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