81,769 research outputs found
Quakes in Solid Quark Stars
A starquake mechanism for pulsar glitches is developed in the solid quark
star model. It is found that the general glitch natures (i.e., the glitch
amplitudes and the time intervals) could be reproduced if solid quark matter,
with high baryon density but low temperature, has properties of shear modulus
\mu = 10^{30~34} erg/cm^3 and critical stress \sigma_c = 10^{18~24} erg/cm^3.
The post-glitch behavior may represent a kind of damped oscillations.Comment: 11 pages, 4 figures (but Fig.3 is lost), a complete version can be
obtained by http://vega.bac.pku.edu.cn/~rxxu/publications/index_P.htm, a new
version to be published on Astroparticle Physic
The gravitational field of a global monopole
We present an exact solution to the non-linear equation which describes a
global monopole in the flat space. We re-examine the metric and the geodesics
outside the global monopole. We will see that a global monopole produces a
repulsive gravitational field outside the core in addition to a solid angular
deficit. The lensing property of the global monopole and the global
monopole-antimonopole annihilation mechanism are studied.Comment: 8 pages, no figure
Comparison of different measures for quantum discord under non-Markovian noise
Two geometric measures for quantum discord were recently proposed by Modi et
al. [Phys. Rev. Lett. 104, 080501 (2010)] and Dakic et al. [Phys. Rev. Lett.
105, 190502 (2010)]. We study the similarities and differences for total
quantum correlations of Bell-diagonal states using these two geometry-based
quantum discord and the original quantum discord. We show that, under
non-Markovian dephasing channels, quantum discord and one of the geometric
measures stay constant for a finite amount of time, but not the other geometric
measure. However, all the three measures share a common sudden change point.
Our study on critical point of sudden transition might be useful for keeping
long time total quantum correlations under decoherence.Comment: 10 pages, 3 figures submitted for publicatio
Enhancement of quantum correlations for the system of cavity QED by applying bang-bang pulses
We propose a scheme of increasing quantum correlations for the cavity quantum
electrodynamics system consisting of two noninteracting two-level atoms each
locally interacting with its own quantized field mode by bang-bang pulses. We
investigate the influence of the bang-bang pulses on the dynamics of quantum
discord, entanglement, quantum mutual information and classical correlation
between the two atoms. It is shown that the amount of quantum discord and
entanglement of the two atoms can be improved by applying the bang-bang pulses.Comment: 6 pages, 5 figure
Alternate proof of the Rowe-Rosensteel proposition and seniority conservation
For a system with three identical nucleons in a single- shell, the states
can be written as the angular momentum coupling of a nucleon pair and the odd
nucleon. The overlaps between these non-orthonormal states form a matrix which
coincides with the one derived by Rowe and Rosensteel [Phys. Rev. Lett. {\bf
87}, 172501 (2001)]. The propositions they state are related to the eigenvalue
problems of the matrix and dimensions of the associated subspaces. In this
work, the propositions will be proven from the symmetric properties of the
symbols. Algebraic expressions for the dimension of the states, eigenenergies
as well as conditions for conservation of seniority can be derived from the
matrix.Comment: 9 pages, no figur
Critical Current Density and Resistivity of MgB2 Films
The high resistivity of many bulk and film samples of MgB2 is most readily
explained by the suggestion that only a fraction of the cross-sectional area of
the samples is effectively carrying current. Hence the supercurrent (Jc) in
such samples will be limited by the same area factor, arising for example from
porosity or from insulating oxides present at the grain boundaries. We suggest
that a correlation should exist, Jc ~ 1/{Rho(300K) - Rho(50K)}, where Rho(300K)
- Rho(50K) is the change in the apparent resistivity from 300 K to 50 K. We
report measurements of Rho(T) and Jc for a number of films made by hybrid
physical-chemical vapor deposition which demonstrate this correlation, although
the "reduced effective area" argument alone is not sufficient. We suggest that
this argument can also apply to many polycrystalline bulk and wire samples of
MgB2.Comment: 11 pages, 3 figure
Study of the neutron skin thickness of Pb in mean field models
We study whether the neutron skin thickness of Pb
originates from the bulk or from the surface of the neutron and proton density
distributions in mean field models. We find that the size of the bulk
contribution to of Pb strongly depends on the slope
of the nuclear symmetry energy, while the surface contribution does not. We
note that most mean field models predict a neutron density for Pb
between the halo and skin type limits. We investigate the dependence of parity-
violating electron scattering at the kinematics of the PREX experiment on the
shape of the nucleon densities predicted by the mean field models for
Pb. We find an approximate formula for the parity-violating asymmetry
in terms of the central radius and the surface diffuseness of the nucleon
densities of Pb in these models.Comment: 5 pages, 2 figures, proceedings MBC 2011 - Many body correlations
from dilute to dense nuclear systems - IHP PARI
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