62,875 research outputs found
Equation of State in 2+1 Flavor QCD at High Temperatures
We calculate the Equation of State at high temperatures in 2+1 flavor QCD
using the highly improved staggered quark action. We study the lattice spacing
dependence of the pressure at high temperatures using lattices with temporal
extent and and perform continuum extrapolations. We
also give a continuum estimate for the Equation of State up to temperatures
GeV, which are then compared with results of the weak-coupling
calculations. We find a reasonably good agreement with the weak-coupling
calculations at the highest temperatures.Comment: RevTeX, 16 pages, 16 figures, published versio
Evaluation of roughness lengths at the NSSL- WKY meteorological tower
Wind and temperature sensors installed on NSSL-WKY /Oklahoma City/ meteorological tower to evaluate roughness length
Evidence for crossed Andreev reflection in superconductor-ferromagnet hybrid structures
We have measured the non-local resistance of aluminum-iron spin-valve
structures fabricated by e-beam lithography and shadow evaporation. The sample
geometry consists of an aluminum bar with two or more ferromagnetic wires
forming point contacts to the aluminum at varying distances from each other. In
the normal state of aluminum, we observe a spin-valve signal which allows us to
control the relative orientation of the magnetizations of the ferromagnetic
contacts. In the superconducting state, at low temperatures and excitation
voltages well below the gap, we observe a spin-dependent non-local resistance
which decays on a smaller length scale than the normal-state spin-valve signal.
The sign, magnitude and decay length of this signal is consistent with
predictions made for crossed Andreev reflection (CAR).Comment: RevTeX, 4 page
Quark deconfinement in high-mass neutron stars
In this paper, we explore whether or not quark deconfinement may occur in
high-mass neutron stars such as J1614-2230 (1.97 \pm 0.04 M_Sun) and J0348+0432
(2.01 \pm 0.04 M_Sun). Our study is based on a non-local extension of the SU(3)
Nambu Jona-Lasinio (n3NJL) model with repulsive vector interactions among the
quarks. This model goes beyond the frequently used local version of the Nambu
Jona-Lasinio (NJL) model by accounting for several key features of QCD which
are not part of the local model. Confined hadronic matter is treated in the
framework of non-linear relativistic mean field theory. We find that both the
local as well as the non-local NJL model predict the existence of extended
regions of mixed quark-hadron (quark-hybrid) matter in high-mass neutron stars
with masses of 2.1 to 2.4 M_Sun. Pure quark matter in the cores of neutron
stars is obtained for certain parametrizations of the hadronic lagrangian and
choices of the vector repulsion among quarks. The radii of high-mass neutron
stars with quark-hybrid matter and/or pure quark matter cores in their centers
are found to lie in the canonical range of 12 to 13 km.Comment: 31 pages, 17 figures, PRC accepted versio
Quark-hybrid matter in the cores of massive neutron stars
Using a nonlocal extension of the SU(3) Nambu-Jona Lasinio model, which
reproduces several of the key features of Quantum Chromodynamics, we show that
mixed phases of deconfined quarks and confined hadrons (quark-hybrid matter)
may exist in the cores of neutron stars as massive as around 2.1 M_Sun. The
radii of these objects are found to be in the canonical range of
km. According to our study, the transition to pure quark matter does not occur
in stable neutron stars, but is shifted to neutron stars which are unstable
against radial oscillations. The implications of our study for the recently
discovered, massive neutron star PSR J1614-2230, whose gravitational mass is
, are that this neutron star may contain an extended
region of quark-hybrid matter at it center, but no pure quark matter.Comment: 13 pages, 3 figure
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