9,826 research outputs found
Modeling Hybrid Stars
We study the so called hybrid stars, which are hadronic stars that contain a
core of deconfined quarks. For this purpose, we make use of an extended version
of the SU(3) chiral model. Within this approach, the degrees of freedom change
naturally from hadrons (baryon octet) to quarks (u, d, s) as the temperature
and/or density increases. At zero temperature we are still able to reproduce
massive stars, even with the inclusion of hyperons.Comment: To appear in the proceedings of Conference C12-08-0
Isospin dependent kaon and antikaon optical potentials in dense hadronic matter
Isospin effects on the optical potentials of kaons and antikaons in dense
hadronic matter are investigated using a chiral SU(3) model. These effects are
important for asymmetric heavy ion collision experiments. In the present work
the dispersion relations are derived for kaons and antikaons, compatible with
the low energy scattering data, within our model approach. The relations result
from the kaonic interactions with the nucleons, vector mesons and scalar mesons
in the asymmetric nuclear matter. The isospin asymmetry effects arising from
the interactions with the vector-isovector - meson as well as the scalar
isovector mesons are considered. The density dependence of the isospin
asymmetry is seen to be appreciable for the kaon and antikaon optical
potentials. This can be particularly relevant for the future accelerator
facility FAIR at GSI, where experiments using neutron rich beams are planned to
be used in the study of compressed baryonic matter.Comment: 21 pages, 7 figure
The application of the Quark-Hadron Chiral Parity-Doublet Model to neutron star matter
The Quark-Hadron Chiral Parity-Doublet model (QP) is applied to
calculate compact star properties in the presence of a deconfinement phase
transition. Within this model, a consistent description of nuclear matter
properties, chiral symmetry restoration, and a transition from hadronic to
quark and gluonic degrees of freedom is possible within one unified approach.
We find that the equation of state obtained is consistent with recent
perturbative quantum chromodynamics (QCD) results and is able to accommodate
observational constraints of massive and small neutron stars. Furthermore, we
show that important features of the equation of state, such as the symmetry
energy and its slope, are well within their observational constraints.Comment: 8 pages, 9 figures and 1 tabl
Task rules, working memory, and fluid intelligence
Many varieties of working memory have been linked to fluid intelligence. In Duncan et al. (Journal of Experimental Psychology:General 137:131â148, 2008), we described limited working memory for new task rules: When rules are complex, some may fail in their control of behavior, though they are often still available for explicit recall. Unlike other kinds of working memory, load is determined in this case not by real-time performance demands, but by the total complexity of the task instructions. Here, we show that the correlation with fluid intelligence is stronger for this aspect of working memory than for several other, more traditional varietiesâincluding simple and complex spans and a test of visual short-term memory. Any task, we propose, requires construction of a mental control program that aids in segregating and assembling multiple task parts and their controlling rules. Fluid intelligence is linked closely to the efficiency of constructing such programs, especially when behavior is complex and novel
Chiral Hadronic Mean Field Model including Quark Degrees of Freedom
In an approach inspired by Polyakov loop extended NJL models, we present a
nonlinear hadronic SU(3) sigma-omega mean field model augmented by quark
degrees of freedom. By introducing the effective Polyakov loop related scalar
field \Phi and an associated effective potential, the model includes all known
hadronic degrees of freedom at low temperatures and densities as well as a
quark phase at high temperatures and densities. Hadrons in the model exhibit a
finite volume in order to suppress baryons at high T and \mu. This ensures that
the right asymptotic degrees of freedom are attained for the description of
strongly interacting matter and allows to study the QCD phase diagram in a wide
range of temperatures and chemical potentials. Therefore, with this model it is
possible to study the phase transition of chiral restoration and deconfinement.
In this paper, the impact of quarks on the resulting phase diagram is shown.
The results from the chiral model are compared to recent data from lattice QCD.Comment: 25 pages, 10 figure
On the relationships between self-reported bicycling injuries and perceived risk among cyclists in Queensland, Australia
The focus of governments on increasing active travel has motivated renewed interest in cycling safety. Bicyclists are up to 20 times more likely to be involved in serious injury crashes than drivers so understanding the relationship among factors in bicyclist crash risk is critically important for identifying effective policy tools, for informing bicycle infrastructure investments, and for identifying high risk bicycling contexts. This study aims to better understand the complex relationships between bicyclist self reported injuries resulting from crashes (e.g. hitting a car) and non-crashes (e.g. spraining an ankle) and perceived risk of cycling as a function of cyclist exposure, rider conspicuity, riding environment, rider risk aversion, and rider ability. Self reported data from 2,500 Queensland cyclists are used to estimate a series of seemingly unrelated regressions to examine the relationships among factors. The major findings suggest that perceived risk does not appear to influence injury rates, nor do injury rates influence perceived risks of cycling. Riders who perceive cycling as risky tend not to be commuters, do not engage in group riding, tend to always wear mandatory helmets and front lights, and lower their perception of risk by increasing days per week of riding and by increasing riding proportion on bicycle paths. Riders who always wear helmets have lower crash injury risk. Increasing the number of days per week riding tends to decrease both crash injury and non crash injury risk (e.g. a sprain). Further work is needed to replicate some of the findings in this study
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