1,202 research outputs found
Thermodynamics of baryonic matter with strangeness within non-relativistic energy density functional model
We study the thermodynamical properties of compressed baryonic matter with
strangeness within non-relativistic energy density functional models with a
particular emphasis on possible phase transitions found earlier for a simple
-mixture. The aim of the paper is twofold: I) examining the
phase structure of the complete system, including the full baryonic octet and
II) testing the sensitivity of the results to the model parameters. We find
that, associated to the onset of the different hyperonic families, up to three
separate strangeness-driven phase transitions may occur. Consequently, a large
fraction of the baryonic density domain is covered by phase coexistence with
potential relevance for (proto)-neutron star evolution. It is shown that the
presence of a phase transition is compatible both with the observational
constraint on the maximal neutron star mass, and with the present experimental
information on hypernuclei. In particular we show that two solar mass neutron
stars are compatible with important hyperon content. Still, the parameter space
is too large to give a definitive conclusion of the possible occurrence of a
strangeness driven phase transition, and further constraints from
multiple-hyperon nuclei and/or hyperon diffusion data are needed.Comment: 11 pages, 7 figure
Modification of magicity towards the dripline and its impact on electron-capture rates for stellar core-collapse
The importance of microphysical inputs from laboratory nuclear experiments
and theoretical nuclear structure calculations in the understanding of the core
collapse dynamics, and the subsequent supernova explosion, is largely
recognized in the recent literature. In this work, we analyze the impact of the
masses of very neutron rich nuclei on the matter composition during collapse,
and the corresponding electron capture rate. To this aim, we introduce an
empirical modification of the popular Duflo-Zuker mass model to account for
possible shell quenching far from stability, and study the effect of the
quenching on the average electron capture rate. We show that the preeminence of
the and closed shells in the collapse dynamics is considerably
decreased if the shell gaps are reduced in the region of Ni and beyond.
As a consequence, local modifications of the overall electron capture rate up
to 30\% can be expected, with integrated values strongly dependent on the
stiffness of magicity quenching and progenitor mass and potential important
consequences on the entropy generation, the neutrino emissivity, and the mass
of the core at bounce. Our work underlines the importance of new experimental
measurements in this region of the nuclear chart, the most crucial information
being the nuclear mass and the Gamow-Teller strength. Reliable microscopic
calculations of the associated elementary rate, in a wide range of temperatures
and electron densities, optimized on these new empirical information, will be
additionally needed to get quantitative predictions of the collapse dynamics.Comment: 12 pages, 10 figure
Particle size distribution of suspended solids in the Chesapeake Bay entrance and adjacent shelf waters
Characteristics of suspended solids, including total suspended matter, total suspended inorganics, total suspended organics, particle size distribution, and the presence of the ten most prominent particle types were determined. Four research vessels simultaneously collected samples along four transects. Samples were collected within a 2-hour period that coincided with the maximum ebb penetration of Chesapeake Bay outwelling. The distribution of primary and secondary particle size modes indicate the presence of a surface or near-surface plume, possibly associated with three sources: (1) runoff, (2) resuspension of material within the Bay, and/or (3) resuspension of material in the area of shoals at the Bay mouth. Additional supportive evidence for this conclusion is illustrated with ocean color scanner data
Hyperons in neutron stars and supernova cores
The properties of compact stars and their formation processes depend on many
physical ingredients. The composition and the thermodynamics of the involved
matter is one of them. We will investigate here uniform strongly interacting
matter at densities and temperatures, where potentially other components than
free nucleons appear such as hyperons, mesons or even quarks. In this paper we
will put the emphasis on two aspects of stellar matter with non-nucleonic
degrees of freedom. First, we will study the phase diagram of baryonic matter
with strangeness, showing that the onset of hyperons, as that of quark matter,
could be related to a very rich phase structure with a large density domain
covered by phase coexistence. Second, we will investigate thermal effects on
the equation of state (EoS), showing that they favor the appearance of
non-nucleonic particles. We will finish by reviewing some recent results on the
impact of non-nucleonic degrees freedom in compact star mergers and
core-collapse events, where thermal effects cannot be neglected.Comment: 20 pages, 14 figures, contribution to the EPJA topical issue "Exotic
matter in neutron stars
Hyperons in neutron star matter within relativistic mean-field models
Since the discovery of neutron stars with masses around 2 solar masses the
composition of matter in the central part of these massive stars has been
intensively discussed. Within this paper we will (re)investigate the question
of the appearance of hyperons. To that end we will perform an extensive
parameter study within relativistic mean field models. We will show that it is
possible to obtain high mass neutron stars (i) with a substantial amount of
hyperons, (ii) radii of 12-13 km for the canonical mass of 1.4 solar masses,
and (iii) a spinodal instability at the onset of hyperons. The results depend
strongly on the interaction in the hyperon-hyperon channels, on which only very
little information is available from terrestrial experiments up to now.Comment: 15 pages, 10 figure
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
Mixed phases of color superconducting quark matter
We examine electrically and color neutral quark matter in beta-equilibrium
focusing on the possibility of mixed phases between different color
superconducting phases. To that end we apply the Gibbs criterion to ensure
phase equilibrium and discuss the external conditions under which these mixed
phases can occur. Neglecting surface and Coulomb effects we find a rich
structure of different mixed phases with up to four components, including 2SC
and CFL matter as well as more ``exotic'' components, like a phase with us- and
ds-pairing but without ud-pairing. Preliminary estimates indicate, however,
that the mixed phases become unstable if surface and Coulomb effects are
included.Comment: 22 pages, 9 figures, v2: minor changes in the text, version to appear
in Nucl. Phys.
EuLerian Identification of ascending AirStreams (ELIAS 2.0) in numerical weather prediction and climate models - Part 2: Model application to different datasets
Warm conveyor belts (WCBs) affect the atmospheric dynamics in midlatitudes and are highly relevant for total and extreme precipitation in many parts of the extratropics. Thus, these airstreams and their effect on midlatitude weather should be well represented in numerical weather prediction (NWP) and climate models. This study applies newly developed convolutional neural network (CNN) models which allow the identification of footprints of WCB inflow, ascent, and outflow from a limited number of predictor fields at comparably low spatiotemporal resolution. The goal of the study is to demonstrate the versatile applicability of the CNN models to different datasets and that their application yields qualitatively and quantitatively similar results as their trajectory-based counterpart, which is most frequently used to objectively identify WCBs. The trajectory-based approach requires data at higher spatiotemporal resolution, which are often not available, and is computationally more expensive. First, an application to reanalyses reveals that the well-known relationship between WCB ascent and extratropical cyclones as well as between WCB outflow and blocking anticyclones is also found for WCB footprints identified with the CNN models. Second, the application to Japanese 55-year reanalyses shows how the CNN models may be used to identify erroneous predictor fields that deteriorate the models\u27 reliability. Third, a verification of WCBs in operational European Centre for Medium-Range Weather Forecasts (ECMWF) ensemble forecasts for three Northern Hemisphere winters reveals systematic biases over the North Atlantic with both the trajectory-based approach and the CNN models. The ensemble forecasts\u27 skill tends to be lower when being evaluated with the trajectory approach due to the fine-scale structure of WCB footprints in comparison to the rather smooth CNN-based WCB footprints. A final example demonstrates the applicability of the CNN models to a convection-permitting simulation with the ICOsahedral Nonhydrostatic (ICON) NWP model. Our study illustrates that deep learning methods can be used efficiently to support process-oriented understanding of forecast error and model biases and opens numerous directions for future research
Self-consistent parametrization of the two-flavor isotropic color-superconducting ground state
Lack of Lorentz invariance of QCD at finite quark chemical potential in
general implies the need of Lorentz non-invariant condensates for the
self-consistent description of the color-superconducting ground state.
Moreover, the spontaneous breakdown of color SU(3) in this state naturally
leads to the existence of SU(3) non-invariant non-superconducting expectation
values. We illustrate these observations by analyzing the properties of an
effective 2-flavor Nambu-Jona-Lasinio type Lagrangian and discuss the
possibility of color-superconducting states with effectively gapless fermionic
excitations. It turns out that the effect of condensates so far neglected can
yield new interesting phenomena.Comment: 16 pages, 3 figure
Everything Hits at Once: How Remote Rainfall Matters for the Prediction of the 2021 North American Heat Wave
In June 2021, Western North America experienced an intense heat wave with unprecedented temperatures and far-reaching socio-economic consequences. Anomalous rainfall in the West Pacific triggers a cascade of weather events across the Pacific, which build up a high-amplitude ridge over Canada and ultimately lead to the heat wave. We show that the response of the jet stream to diabatically enhanced ascending motion in extratropical cyclones represents a predictability barrier with regard to the heat wave magnitude. Therefore, probabilistic weather forecasts are only able to predict the extremity of the heat wave once the complex cascade of weather events is captured. Our results highlight the key role of the sequence of individual weather events in limiting the predictability of this extreme event. We therefore conclude that it is not sufficient to consider such rare events in isolation but it is essential to account for the whole cascade over different spatiotemporal scales
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