1,159 research outputs found
Some aspects of the phase diagram of nuclear matter relevant to compact stars
Dense matter as it can be found in core-collapse supernovae and neutron stars
is expected to exhibit different phase transitions which impact the matter
composition and the equation of state, with important consequences on the
dynamics of core-collapse supernova explosion and on the structure of neutron
stars. In this paper we will address the specific phenomenology of two of such
transitions, namely the crust-core solid-liquid transition at sub-saturation
density, and the possible strange transition at super-saturation density in the
presence of hyperonic degrees of freedom. Concerning the neutron star
crust-core phase transition at zero and finite temperature, it will be shown
that, as a consequence of the presence of long-range Coulomb interactions, a
clusterized phase is expected which is not accessible in the grand-canonical
ensemble. A specific quasi-particle model will be introduced and some
quantitative results relevant for the supernova dynamics will be shown. The
opening of hyperonic degrees of freedom at higher densities corresponding to
the neutron stars core also modifies the equation of state. The general
characteristics and order of phase transitions in this regime will be analyzed
in the framework of a self-consistent mean-field approach.Comment: arXiv admin note: substantial text overlap with arXiv:1206.4924,
arXiv:1301.695
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Use of ArcGIS in Environmental Monitoring at Idaho National Laboratory
The Idaho National Laboratory is a U.S. Department of Energy site located in southeastern Idaho. The INL is required to perform environmental monitoring of anthropogenically introduced contaminants. One primary contaminant of interest is radioactive Cs-137 which is resident in INL soils due to past operational activities and atmospheric weapons testing. Collection of field data is performed using vehicle mounted and portable radiation detector units. All data is combined in ArcGIS and displayed over georeferenced satellite images and digital elevation models. The use of the ArcGIS geostatistical analysis package enhances the ability to look for areas of higher Cs-137 concentration. Combining current monitoring results with meteorological wind pattern maps allows for siting of new and improved monitoring locations. Use of the ArcGIS package provides an integrated analysis and mapping protocol for use in radioactive contaminant monitoring
Two regularizations - two different models of Nambu-Jona-Lasinio
Two variants of the Nambu--Jona-Lasinio model -- the model with 4-dimensional
cutoff and the model with dimensionally-analytical regularization -- are
systematically compared. It is shown that they are, in essence, two different
models of light-quark interaction. In the mean-field approximation the
distinction becomes apparent in a behavior of scalar amplitude near the
threshold. For 4-dimensional cutoff the pole term can be extracted, which
corresponds to sigma-meson. For dimensionally-analytical regularization the
singularity of the scalar amplitude is not pole, and this singularity is quite
disappeared at some value of the regularization parameter.
Still more essential distinction of these models exists in the
next-to-leading order of mean-field expansion. The calculations of meson
contributions in the quark chiral condensate and in the dynamical quark mass
demonstrate, that these contributions though their relatively smallness can
destabilize the Nambu--Jona-Lasinio model with 4-dimensional cutoff. On the
contrary, the Nambu--Jona-Lasinio model with dimensionally-analytical
regularization is stabilized with the next-to-leading order, i.e. the value of
the regularization parameter shifts to the stability region, where these
contributions decrease.Comment: 14 pages; Journal version; parameter fixing procedure is modifie
Phase diagram of neutron-rich nuclear matter and its impact on astrophysics
Dense matter as it can be found in core-collapse supernovae and neutron stars
is expected to exhibit different phase transitions which impact the matter
composition and equation of state, with important consequences on the dynamics
of core-collapse supernova explosion and on the structure of neutron stars. In
this paper we will address the specific phenomenology of two of such
transitions, namely the crust-core solid-liquid transition at sub-saturation
density, and the possible strange transition at super-saturation density in the
presence of hyperonic degrees of freedom. Concerning the neutron star
crust-core phase transition at zero and finite temperature, it will be shown
that, as a consequence of the presence of long-range Coulomb interactions, the
equivalence of statistical ensembles is violated and a clusterized phase is
expected which is not accessible in the grand-canonical ensemble. A specific
quasi-particle model will be introduced to illustrate this anomalous
thermodynamics and some quantitative results relevant for the supernova
dynamics will be shown. The opening of hyperonic degrees of freedom at higher
densities corresponding to the neutron stars core modifies the equation of
state. The general characteristics and order of phase transitions in this
regime will be analyzed in the framework of a self-consistent mean-field
approach.Comment: Invited Talk given at the 11th International Conference on
Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1,
2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference
Series (JPCS
Anisotropic admixture in color-superconducting quark matter
The analysis of color-superconducting two-flavor deconfined quark matter at
moderate densities is extended to include a particular spin-1 Cooper pairing of
those quarks which do not participate in the standard spin-0 diquark
condensate. (i) The relativistic spin-1 gap Delta' implies spontaneous
breakdown of rotation invariance manifested in the form of the quasi-fermion
dispersion law. (ii) The critical temperature of the anisotropic component is
approximately given by the relation T_c'~ Delta'(T=0)/3. (iii) For massless
fermions the gas of anisotropic Bogolyubov-Valatin quasiquarks becomes
effectively gapless and two-dimensional. Consequently, its specific heat
depends quadratically on temperature. (iv) All collective Nambu-Goldstone
excitations of the anisotropic phase have a linear dispersion law and the whole
system remains a superfluid. (v) The system exhibits an electromagnetic
Meissner effect.Comment: v2: references added, angular dependence of the gap clarified, v3:
extended discussion, typo in eq. (5) corrected, version accepted for
publication in PR
Meson loop effects in the NJL model at zero and non-zero temperature
We compare two different possibilities to include meson-loop corrections in
the Nambu-Jona-Lasinio model: a strict 1/N_c-expansion in next-to-leading order
and a non-perturbative scheme corresponding to a one-meson-loop approximation
to the effective action. Both schemes are consistent with chiral symmetry, in
particular with the Goldstone theorem and the Gell-Mann-Oakes-Renner relation.
The numerical part at zero temperature focuses on the pion and the rho-meson
sector. For the latter the meson-loop-corrections are crucial in order to
include the dominant rho -> pipi-decay channel, while the standard Hartree +
RPA approximation only contains unphysical qqbar-decay channels. We find that
m_\pi, f_\pi, and quantities related to the rho-meson self-energy can
be described reasonably with one parameter set in the 1/N_c-expansion scheme,
whereas we did not succeed to obtain such a fit in the non-perturbative scheme.
We also investigate the temperature dependence of the quark condensate. Here we
find consistency with chiral perturbation theory to lowest order. Similarities
and differences of both schemes are discussed.Comment: 51 pages, 18 figures, to be published in Physics of Atomic Nuclei,
the volume dedicated to the 90th birthday of A.B. Migdal, error in Eq. 4.22
correcte
Surface effects in color superconducting strange-quark matter
Surface effects in strange-quark matter play an important role for certain
observables which have been proposed in order to identify strange stars, and
color superconductivity can strongly modify these effects. We study the surface
of color superconducting strange-quark matter by solving the
Hartree-Fock-Bogoliubov equations for finite systems ("strangelets") within the
MIT bag model, supplemented with a pairing interaction. Due to the bag-model
boundary condition, the strange-quark density is suppressed at the surface.
This leads to a positive surface charge, concentrated in a layer of ~1 fm below
the surface, even in the color-flavor locked (CFL) phase. However, since in the
CFL phase all quarks are paired, this positive charge is compensated by a
negative charge, which turns out to be situated in a layer of a few tens of fm
below the surface, and the total charge of CFL strangelets is zero. We also
study the surface and curvature contributions to the total energy. Due to the
strong pairing, the energy as a function of the mass number is very well
reproduced by a liquid-drop type formula with curvature term.Comment: 13 pages, v2: more detailed explanations, discussion adde
Predicting Climate-Driven Coastlines With a Simple and Efficient Multiscale Model
Ocean-basin-scale climate variability produces shifts in wave climates and water levels affecting the coastlines of the basin. Here we present a hybrid shoreline change?foredune erosion model (A COupled CrOss-shOre, loNg-shorE, and foreDune evolution model, COCOONED) intended to inform coastal planning and adaptation. COCOONED accounts for coupled longshore and cross-shore processes at different timescales, including sequencing and clustering of storm events, seasonal, interannual, and decadal oscillations by incorporating the effects of integrated varying wave action and water levels for coastal hazard assessment. COCOONED is able to adapt shoreline change rates in response to interactions between longshore transport, cross-shore transport, water level variations, and foredune erosion. COCOONED allows for the spatial and temporal extension of survey data using global data sets of waves and water levels for assessing the behavior of the shoreline at multiple time and spatial scales. As a case study, we train the model in the period 2004?2014 (11 years) with seasonal topographic beach profile surveys from the North Beach Sub-cell (NBSC) of the Columbia River Littoral Cell (Washington, USA).We explore the shoreline response and foredune erosion along 40 km of beach at several timescales during the period 1979?2014 (35 years), revealing an accretional trend producing reorientation of the beach, cross-shore accretional, and erosional periods through time (breathing) and alternating beach rotations that are correlated with climate indices.J. A. A.
Antolínez and F. J. Méndez
acknowledge the support of the
Spanish “Ministerio de Economia y
Competitividad” under Grant
BIA2014-59643-R
Photon emission from bare quark stars
We investigate the photon emission from the electrosphere of a quark star. It
is shown that at temperatures T\sim 0.1-1 MeV the dominating mechanism is the
bremsstrahlung due to bending of electron trajectories in the mean Coulomb
field of the electrosphere. The radiated energy for this mechanism is much
larger than that for the Bethe-Heitler bremsstrahlung. The energy flux from the
mean field bremsstrahlung exceeds the one from the tunnel e^{+}e^{-} pair
creation as well. We demonstrate that the LPM suppression of the photon
emission is negligible.Comment: 35 pages, 5 figure
Dispersive analysis of K_{L mu3} and K_{L e3} scalar and vector form factors using KTeV data
Using the published KTeV samples of K_L --> pi^{\pm} e^{\mp} nu and K_L -->
pi^{\pm} mu^{\mp} nu decays [1], we perform a reanalysis of the scalar and
vector form factors based on the dispersive parameterization [2,3]. We obtain
phase space integrals I^e_K = 0.15446 \pm 0.00025 and I^{mu}_K = 0.10219 \pm
0.00025. For the scalar form factor parameterization, the only free parameter
is the normalized form factor value at the Callan-Treiman point (C); our best
fit results in ln C = 0.1915 \pm 0.0122. We also study the sensitivity of C to
different parametrizations of the vector form factor. The results for the phase
space integrals and C are then used to make tests of the Standard Model.
Finally, we compare our results with lattice QCD calculations of F_K/F_pi and
f_+(0).Comment: 9 pages, 3 figures, to be published in PR
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