18,842 research outputs found
Geometrical Expression for the Angular Resolution of a Network of Gravitational-Wave Detectors
We report for the first time general geometrical expressions for the angular
resolution of an arbitrary network of interferometric gravitational-wave (GW)
detectors when the arrival-time of a GW is unknown. We show explicitly elements
that decide the angular resolution of a GW detector network. In particular, we
show the dependence of the angular resolution on areas formed by projections of
pairs of detectors and how they are weighted by sensitivities of individual
detectors. Numerical simulations are used to demonstrate the capabilities of
the current GW detector network. We confirm that the angular resolution is poor
along the plane formed by current LIGO-Virgo detectors. A factor of a few to
more than ten fold improvement of the angular resolution can be achieved if the
proposed new GW detectors LCGT or AIGO are added to the network. We also
discuss the implications of our results for the design of a GW detector
network, optimal localization methods for a given network, and electromagnetic
follow-up observations.Comment: 13 pages, for Phys. Rev.
Quantum correlations in topological quantum phase transitions
We study the quantum correlations in a 2D system that possesses a topological
quantum phase transition. The quantumness of two-body correlations is measured
by quantum discord. We calculate both the correlation of two local spins and
that of an arbitrary spin with the rest of the lattice. It is notable that
local spins are classically correlated, while the quantum correlation is hidden
in the global lattice. This is different from other systems which are not
topologically orderd. Moreover, the mutual information and global quantum
discord show critical behavior in the topological quantum phase transition.Comment: 6 pages, 3 figure
Effects of momentum-dependent nuclear potential on two-nucleon correlation functions and light cluster production in intermediate energy heavy-ion collisions
Using an isospin- and momentum-dependent transport model, we study the
effects due to the momentum dependence of isoscalar nuclear potential as well
as that of symmetry potential on two-nucleon correlation functions and light
cluster production in intermediate energy heavy-ion collisions induced by
neutron-rich nuclei. It is found that both observables are affected
significantly by the momentum dependence of nuclear potential, leading to a
reduction of their sensitivity to the stiffness of nuclear symmetry energy.
However, the t/He ratio remains a sensitive probe of the density
dependence of nuclear symmetry energy.Comment: 20 pages, 11 figure
High-energy behavior of the nuclear symmetry potential in asymmetric nuclear matter
Using the relativistic impulse approximation with empirical NN scattering
amplitude and the nuclear scalar and vector densities from the relativistic
mean-field theory, we evaluate the Dirac optical potential for neutrons and
protons in asymmetric nuclear matter. From the resulting Schr\"{o}%
dinger-equivalent potential, the high energy behavior of the nuclear symmetry
potential is studied. We find that the symmetry potential at fixed baryon
density is essentially constant once the nucleon kinetic energy is greater than
about 500 MeV. Moreover, for such high energy nucleon, the symmetry potential
is slightly negative below a baryon density of about fm
and then increases almost linearly to positive values at high densities. Our
results thus provide an important constraint on the energy and density
dependence of nuclear symmetry potential in asymmetric nuclear matter.Comment: 6 pages, 5 figures, revised version, to appear in PR
Neutrino-cooled Accretion Disks around Spinning Black Holes
We calculate the structure of accretion disk around a spinning black hole for
accretion rates 0.01 - 10 M_sun/s. The model is fully relativistic and treats
accurately the disk microphysics including neutrino emissivity, opacity,
electron degeneracy, and nuclear composition. We find that the accretion flow
always regulates itself to a mildly degenerate state with the proton-to-nucleon
ratio Y_e ~ 0.1 and becomes very neutron-rich. The disk has a well defined
"ignition" radius where neutrino flux raises dramatically, cooling becomes
efficient, and Y_e suddenly drops. We also calculate other characteristic radii
of the disk, including the neutrino-opaque and neutrino-trapping radii, and
show their dependence on the accretion rate. Accretion disks around
fast-rotating black holes produce intense neutrino fluxes which may deposit
enough energy above the disk to generate a GRB jet.Comment: 4 pages, 3 figures; to be published in AIP Conference Proceedings
"Gamma Ray Bursts in the Swift Era," Nov. 29 - Dec. 2, 2005, Washington, D
Continuous topological phase transitions between clean quantum Hall states
Continuous transitions between states with the {\em same} symmetry but
different topological orders are studied. Clean quantum Hall (QH) liquids with
neutral quasiparticles are shown to have such transitions. For clean bilayer
(nnm) states, a continous transition to other QH states (including non-Abelian
states) can be driven by increasing interlayer repulsion/tunneling. The
effective theories describing the critical points at some transitions are
derived.Comment: 4 pages, RevTeX, 2 eps figure
Absorption cross section in warped AdS_3 black hole revisited
We investigate the absorption cross section for minimal-coupled scalars in
the warped AdS_3 black hole. According to our calculation, the cross section
reduces to the horizon area in the low energy limit as usually expected in
contrast to what was previously found. We also calculate the greybody factor
and find that the effective temperatures for the two chiral CFT's are
consistent with that derived from the quasinormal modes. Observing the
conjectured warped AdS/CFT correspondence, we suspect that a specific sector of
the CFT operators with the desired conformal dimension could be responsible for
the peculiar thermal behaviour of the warped AdS_3 black hole.Comment: 16+1 pages, typos corrected, references and footnotes adde
Mean free paths and in-medium scattering cross sections of energetic nucleons in neutron-rich nucleonic matter within the relativistic impulse approximation
The mean free paths and in-medium scattering cross sections of energetic
nucleons in neutron-rich nucleonic matter are investigated using the nucleon
optical potential obtained within the relativistic impulse approximation with
the empirical nucleon-nucleon scattering amplitudes and the nuclear densities
obtained in the relativistic mean field model. It is found that the
isospin-splitting of nucleon mean free paths, sensitive to the imaginary part
of the symmetry potential, changes its sign at certain high kinetic energy. The
in-medium nucleon-nucleon cross sections are analytically and numerically
demonstrated to be essentially independent of the isospin asymmetry of the
medium and increase linearly with density in the high energy region where the
relativistic impulse approximation is applicable.Comment: 13 pages, 6 figure
Leading Chiral Corrections to the Nucleon Generalized Parton Distributions
Using heavy baryon chiral perturbation theory we study the leading chiral
corrections to the complete set of nucleon generalized parton distributions
(GPDs). We compute the leading quark mass and momentum transfer dependence of
the moments of nucleon GPDs through the nucleon off-forward twist-2 matrix
elements. These results are then applied to get insight on the GPDs and their
impact parameter space distributions.Comment: 26 pages, 2 figures; minor revisio
Nuclear symmetry energy and its density slope at normal density extracted from global nucleon optical potentials
Based on the Hugenholtz-Van Hove theorem, it is shown that both the symmetry
energy E and its density slope at normal density
are completely determined by the global nucleon optical potentials
that can be extracted directly from nucleon-nucleus scatterings, (p,n) charge
exchange reactions and single-particle energy levels of bound states. Adopting
a value of for the nucleon effective k-mass in symmetric nuclear
matter at and averaging all phenomenological isovector nucleon
potentials constrained by world data available in the literature since 1969,
the best estimates of MeV and MeV are
simultaneously obtained. Uncertainties involved in the estimates are discussed.Comment: 4 pages including 2 figure
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