4,181 research outputs found
Conditions for Phase Equilibrium in Supernovae, Proto-Neutron and Neutron Stars
We investigate the qualitative properties of phase transitions in a general
way, if not the single particle numbers of the system but only some particular
charges like e.g. baryon number are conserved. In addition to globally
conserved charges we analyze the implications of locally conserved charge
fractions, like e.g. local electric charge neutrality or locally fixed proton
or lepton fractions. The conditions for phase equilibrium are derived and it is
shown, that the properties of the phase transition do not depend on the locally
conserved fractions. Finally, the general formalism is applied to the
liquid-gas phase transition and the hadron-quark phase transition for typical
astrophysical environments like in supernovae, proto-neutron or a neutron
stars. We demonstrate that the Maxwell construction known from
cold-deleptonized neutron star matter with two locally charge neutral phases
requires modifications and further assumptions concerning the applicability for
hot lepton-rich matter. All possible combinations of local and global
conservation laws are analyzed, and the physical meaningful cases are
identified. Several new kinds of mixed phases are presented, as e.g. a locally
charge neutral mixed phase in proto-neutron stars which will disappear during
the cooling and deleptonization of the proto-neutron star.Comment: 18 page
Temporal and Spatial Turbulent Spectra of MHD Plasma and an Observation of Variance Anisotropy
The nature of MHD turbulence is analyzed through both temporal and spatial
magnetic fluctuation spectra. A magnetically turbulent plasma is produced in
the MHD wind-tunnel configuration of the Swarthmore Spheromak Experiment (SSX).
The power of magnetic fluctuations is projected into directions perpendicular
and parallel to a local mean field; the ratio of these quantities shows the
presence of variance anisotropy which varies as a function of frequency.
Comparison amongst magnetic, velocity, and density spectra are also made,
demonstrating that the energy of the turbulence observed is primarily seeded by
magnetic fields created during plasma production. Direct spatial spectra are
constructed using multi-channel diagnostics and are used to compare to
frequency spectra converted to spatial scales using the Taylor Hypothesis.
Evidence for the observation of dissipation due to ion inertial length scale
physics is also discussed as well as the role laboratory experiment can play in
understanding turbulence typically studied in space settings such as the solar
wind. Finally, all turbulence results are shown to compare fairly well to a
Hall-MHD simulation of the experiment.Comment: 17 pages, 17 figures, Submitted to Astrophysical Journa
Labor Force Status Dynamics in the German Labor Market - Individual Heterogeneity and Cyclical Sensitivity
The aggregate average unemployment rate in a given country is essentially the result of individual workers' transitions between the three core labor force states, employment, unemployment, and inactivity. The dynamics of these transitions depend both, on individual duration in a particular state and the transition probabilities between states. Individual transitions, in turn, depend on observable and unobserved factors. Simultaneously, person-specific dynamics may be influenced by swings of the business cycle. This paper analyzes these labor force status dynamics for the East and West German labor market, separately using comprehensive data on monthly transitions from the SOEP. The results show that the experience of high unemployment rates is more sensitive to cyclical behavior for certain demographic groups, specifically unskilled and young workers. Heterogeneity in unemployment and transition rates differ between East and West Germany, as well as between the sexes. In East Germany, all demographic cells are almost entirely detached from the cycle. Women are less influenced by the cycle in their re-employment rate from unemployment to employment.Labor force, unemployment dynamics, business cycle, worker heterogeneity
A new possible quark-hadron mixed phase in protoneutron stars
The phase transition from hadronic matter to quark matter at high density
might be a strong first order phase transition in presence of a large surface
tension between the two phases. While this implies a constant-pressure mixed
phase for cold and catalyzed matter this is not the case for the hot and lepton
rich matter formed in a protoneutron star. We show that it is possible to
obtain a mixed phase with non-constant pressure by considering the global
conservation of lepton number during the stage of neutrino trapping. In turn,
it allows for the appearance of a new kind of mixed phase as long as neutrinos
are trapped and its gradual disappearance during deleptonization. This new
mixed phase, being composed by two electric neutral phases, does not develop a
Coulomb lattice and it is formed only by spherical structures, drops and
bubbles, which can have macroscopic sizes. The disappearance of the mixed phase
at the end of deleptonization might lead to a delayed collapse of the star into
a more compact configuration containing a core of pure quark phase. In this
scenario, a significant emission of neutrinos and, possibly, gravitational
waves are expected.Comment: 4 pages, 4 figure
Improved Polyakov-loop potential for effective models from functional calculations
We investigate the quark backreaction on the Polyakov loop and its impact on
the thermodynamics of quantum chromodynamics. The dynamics of the gluons
generating the Polyakov-loop potential is altered by the presence of dynamical
quarks. However, this backreaction of the quarks has not yet been taken into
account in Polyakov-loop extended model studies. In the present work, we show
within a 2+1 flavour Polyakov-quark-meson model that a quark-improved
Polyakov-loop potential leads to a smoother transition between the
low-temperature hadronic phase and the high-temperature quark-gluon plasma
phase. In particular, we discuss the dependence of our results on the remaining
uncertainties that are the critical temperature and the parametrisation of the
Polyakov-loop potential as well as the mass of the sigma-meson.Comment: 19 pages, 25 figures; version published in Phys. Rev.
Is there Quark Matter in (Low-Mass) Pulsars?
The effect of the QCD phase transition is studied for the mass-radius
relation of compact stars and for hot and dense matter at a given proton
fraction used as input in core-collapse supernova simulations. The phase
transitions to the 2SC and CFL color superconducting phases lead to stable
hybrid star configurations with a pure quark matter core. In supernova
explosions quark matter could be easily produced due to -equilibrium,
small proton fractions and nonvanishing temperatures. A low critical density
for the phase transition to quark matter is compatible with present pulsar mass
measurements.Comment: 4 pages, 3 figures, talk given at the QM2008 conference, Jaipur,
India, February 4-10, 2008, JPG in pres
Strange Fluctuations at RHIC
Robust statistical observables can be used to extract the novel isospin
fluctuations from background contributions in K-short K-plus measurements in
nuclear collisions. To illustrate how this can be done, we present new HIJING
and UrQMD computations of these observables.Comment: 4 pages, 2 figures, talk at Quark Matter 200
Mass, radius, and composition of the outer crust of nonaccreting cold neutron stars
The properties and composition of the outer crust of nonaccreting cold
neutron stars are studied by applying the model of Baym, Pethick, and
Sutherland, which was extended by including higher order corrections of the
atomic binding, screening, exchange and zero-point energy. The most recent
experimental nuclear data from the atomic mass table of Audi, Wapstra, and
Thibault from 2003 is used. Extrapolation to the drip line is utilized by
various state-of-the-art theoretical nuclear models (finite range droplet,
relativistic nuclear field and non-relativistic Skyrme Hartree-Fock
parameterizations). The different nuclear models are compared with respect to
the mass and radius of the outer crust for different neutron star
configurations and the nuclear compositions of the outer crust.Comment: 5 pages, 2 figures, submitted to J. Phys. G, part of the proceedings
of the Nuclear Physics in Astrophysics III conference in Dresde
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