864 research outputs found
Quark matter in compact stars?
Ozel, in a recent reanalysis of EXO 0748-676 observational data
(astro-ph/0605106), concluded that quark matter probably does not exist in the
center of compact stars. We show that the data is actually consistent with the
presence of quark matter in compact stars.Comment: 4 pages, LaTeX; New title and overall rewrite to reflect version
published in Nature. Conclusions unchange
Band gap bowing in NixMg1-xO.
Epitaxial transparent oxide NixMg1-xO (0 ≤ x ≤ 1) thin films were grown on MgO(100) substrates by pulsed laser deposition. High-resolution synchrotron X-ray diffraction and high-resolution transmission electron microscopy analysis indicate that the thin films are compositionally and structurally homogeneous, forming a completely miscible solid solution. Nevertheless, the composition dependence of the NixMg1-xO optical band gap shows a strong non-parabolic bowing with a discontinuity at dilute NiO concentrations of x 0.074 and account for the anomalously large band gap narrowing in the NixMg1-xO solid solution system
SO(10) Cosmic Strings and SU(3) Color Cheshire Charge
Certain cosmic strings that occur in GUT models such as can carry a
magnetic flux which acts nontrivially on objects carrying
quantum numbers. We show that such strings are non-Abelian Alice strings
carrying nonlocalizable colored ``Cheshire" charge. We examine claims made in
the literature that strings can have a long-range, topological
Aharonov-Bohm interaction that turns quarks into leptons, and observe that such
a process is impossible. We also discuss flux-flux scattering using a
multi-sheeted formalism.Comment: 37 Pages, 8 Figures (available upon request) phyzzx, iassns-hep-93-6,
itp-sb-93-6
The Mass Spectrum of Light and Heavy Hadrons from Improved Lattice Actions
We use improved lattice actions for glue, light quarks and heavy quarks for
which we use lattice NRQCD to compute hadron masses. Our results are in good
agreement with experiment, except for charmed hadrons. It seems that charmed
quar ks are not well approximated as heavy quarks nor as light quarks.Comment: 14 pages +6 pages figures, plain-tex fil
Anomalies in Superfluids and a Chiral Electric Effect
We analyze the chiral transport terms in relativistic superfluid
hydrodynamics. In addition to the spontaneously broken symmetry current, we
consider an arbitrary number of unbroken symmetries and extend the results of
arXiv:1105.3733. We suggest an interpretation of some of the new transport
coefficients in terms of chiral and gravitational anomalies. In particular, we
show that with unbroken gauged charges in the system, one can observe a chiral
electric conductivity - a current in a perpendicular direction to the applied
electric field. We present a motivated proposal for the value of the associated
transport coefficient, linking it to the triangle anomaly. Along the way we
present new arguments regarding the interpretation of the anomalous transport
coefficients in normal fluids. We propose a natural generalization of the
chiral transport terms to the case of an arbitrary number of spontaneously
broken symmetry currents.Comment: 30 pages; v2: Onsager-relations argument corrected, references added;
v3: fixed missing line in eq. (38
Phase transitions in neutron star and magnetars and their connection with high energetic bursts in astrophysics
The phase transition from normal hadronic matter to quark matter in neutron
stars (NS) could give rise to several interesting phenomena. Compact stars can
have such exotic states up to their surface (called strange stars (SS)) or they
can have quark core surrounded by hadronic matter, known as hybrid stars (HS).
As the state of matter of the resultant SS/HS is different from the initial
hadronic matter, their masses also differ. Therefore, such conversion leads to
huge energy release, sometimes of the order of ergs. In the present
work we study the qualitative energy released by such conversion. Recent
observations reveal huge surface magnetic field in certain stars, termed
magnetars. Such huge magnetic fields can modify the equations of state (EOS) of
the matter describing the star. Therefore, the mass of magnetars are different
from normal NS. The energy released during the conversion process from neutron
magnetar (NM) to strange magnetar/hybrid magnetar (SS/HS) is different from
normal NS to SS/HS conversion. In this work we calculate the energy release
during the phase transition in magnetars. The energy released during NS to
SS/HS conversion exceeds the energy released during NM to SM/HM conversion. The
energy released during the conversion of NS to SS is always of the order of
ergs. The amount of energy released during such conversion can only
be compared to the energy observed during the gamma ray bursts (GRB). The
energy liberated during NM to HM conversion is few times lesser, and is not
likely to power GRB at cosmological distances. However, the magnetars are more
likely to lose their energy from the magnetic poles and can produce giant
flares, which are usually associated with magnetars.Comment: 14 pages, 4 figures, 4 table
System-size scan of dihadron azimuthal correlations in ultra-relativistic heavy ion collisions
System-size dependence of dihadron azimuthal correlations in
ultra-relativistic heavy ion collision is simulated by a multi-phase transport
model. The structure of correlation functions and yields of associated
particles show clear participant path-length dependences in collision systems
with a partonic phase. The splitting parameter and root-mean-square width of
away-side correlation functions increase with collision system size from
N+N to Au+Au collisions. The double-peak
structure of away-side correlation functions can only be formed in sufficient
"large" collision systems under partonic phase. The contrast between the
results with partonic phase and with hadron gas could suggest some hints to
study onset of deconfinment.Comment: 8 pages, 4 figures, 1 table; Nucl. Phys. A (accepted
Calculating the I=2 Pion Scattering Length Using Tadpole Improved Clover Wilson Action on Coarse Anisotropic Lattices
In an exploratory study, using the tadpole improved clover Wilson quark
action on small, coarse and anisotropic lattices, the scattering
length in the I=2 channel is calculated within quenched approximation. A new
method is proposed which enables us to make chiral extrapolation of our lattice
results without calculating the decay constant on the lattice. Finite volume
and finite lattice spacing errors are analyzed and the results are extrapolated
towards the infinite volume and continuum limit. Comparisons of our lattice
results with the new experiment and the results from Chiral Perturbation Theory
are made. Good agreements are found.Comment: 21 pages, 8 figures, latex file typeset with elsart.cls, minor
change
Quark deconfinement in neutron star cores and the ground state of neutral matter
Whether or not deconfined quark phase exists in neutron star cores and
represents the ground state of neutral matter at moderate densities are open
questions. We use two realistic effective quark models, the three-flavor
Nambu-Jona-Lasinio model and the modified quark-meson coupling model, to
describe the neutron star matter. After constructing possible hybrid equations
of state (EOSes) with unpaired or color superconducting quark phase, we
systematically discuss the observational constraints of neutron stars on the
EOSes. It is found that the neutron star with pure quark matter core is
unstable and the hadronic phase with hyperons is denied, while hybrid EOSes
with two-flavor color superconducting phase or unpaired quark matter phase are
both allowed by the tight and most reliable constraints from two stars Ter 5 I
and EXO 0748-676. And the hybrid EOS with unpaired quark matter phase is
allowed even compared with the tightest constraint from the most massive pulsar
star PSR J0751+1807. Therefore, we conclude that the ground state of neutral
matter at moderate densities is in deconfined quark phase likely.Comment: 13 pages, 4 figure
Strangelets: Who is Looking, and How?
It has been over 30 years since the first suggestion that the true ground
state of cold hadronic matter might be not nuclear matter but rather strange
quark matter (SQM). Ever since, searches for stable SQM have been proceeding in
various forms and have observed a handful of interesting events but have
neither been able to find compelling evidence for stable strangelets nor to
rule out their existence. I will survey the current status and near future of
such searches with particular emphasis on the idea of SQM from strange star
collisions as part of the cosmic ray flux.Comment: Talk given at International Conference on Strangeness in Quark
Matter, 2006. 8 pages. 1 figur
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