1,270 research outputs found
Dependence of the Chiral Symmetry Restoration Transition on the Quark Self-Energy Kernel
The dependence of the dressed quark propagator on the quark chemical
potential is investigated in various models based on the Dyson-Schwinger
equations. We find that the critical chemical potential of the chiral symmetry
restoration transition is strongly dependent on the nature of the interaction
kernel in the infrared region.Comment: 10 pages, 3 figures, minor change to introduction, accepted for
publication in Phys. Lett.
Dynamics of trending topics between social media, news, and scientific literature
Information is disseminating more rapidly in today\u27s world than ever before in history. Every now and then, topics simultaneously gain massive attention in social media, dominate news headlines, and attract interest from researchers around the globe. While individual domains and networks are studied extensively, one question remains less addressed so far: How does information spread across different channels, considering dynamics between social media, news and, scientific literature? In this paper, we aim to identify frequent patterns in the dissemination of information over multiple channels. Based on an adapted pattern mining algorithm for multivariate time series, we provide strong indications for the existence of distinctive information diffusion effects between social media, news and scientific literature. We find that when all information channels simultaneously cover a certain topic, the preceding period is characterized either by a sole growth of social media coverage or a simultaneous growth of social media and news coverage
A dynamical, confining model and hot quark stars
We explore the consequences of an equation of state (EOS) obtained in a
confining Dyson-Schwinger equation model of QCD for the structure and stability
of nonstrange quark stars at finite-T, and compare the results with those
obtained using a bag-model EOS. Both models support a temperature profile that
varies over the star's volume and the consequences of this are model
independent. However, in our model the analogue of the bag pressure is
(T,mu)-dependent, which is not the case in the bag model. This is a significant
qualitative difference and comparing the results effects a primary goal of
elucidating the sensitivity of quark star properties to the form of the EOS.Comment: 13 pages, 5 figures, epsfig.sty, elsart.sty. Shortened version to
appear in Phys. Lett. B, qualitatively unmodifie
Deconfinement at finite chemical potential
In a confining, renormalisable, Dyson-Schwinger equation model of two-flavour
QCD we explore the chemical-potential dependence of the dressed-quark
propagator, which provides a means of determining the behaviour of the chiral
and deconfinement order parameters, and low-energy pion observables. We find
coincident, first order deconfinement and chiral symmetry restoration
transitions at \mu_c = 375 MeV. f_\pi is insensitive to \mu until \mu \approx
\mu_0 = 0.7 mu_c when it begins to increase rapidly. m_\pi is weakly dependent
on \mu, decreasing slowly with \mu and reaching a minimum 6% less than its
\mu=0 value at \mu=\mu_0. In a two-flavour free-quark gas at \mu=\mu_c the
baryon number density would be approximately 3 \rho_0, where \rho_0=0.16
fm^{-3}; while in such a gas at \mu_0 the density is \rho_0.Comment: 11 pages, 3 figures, epsfig.sty, elsart.st
Joint versus separate inpatient rehabilitation treatment for patients with alcohol use disorder or drug use disorder : an observational study
Background: In many national treatment systems, patients with alcohol use disorders (AUD) and those with drug use disorders (DUD) are treated separately, while other systems provide joint treatment for both kinds of substance use disorders (SUDs). Regarding long-term rehabilitation treatment of DUD and AUD patients, there is however a lack of empirical studies on the comparison between a separate versus joint treatment modality. Methods: Data were gathered from 2 rehabilitation units located in small towns from the same German region. One unit provided treatment to a mixed group of AUD and DUD patients, while the other unit treated the 2 groups separately. Staffing, funding, and treatment programs were otherwise similar between facilities. Data were gathered from standardized routine documentation and standardized interviews. In order to understand correlates of premature treatment termination, a logistic regression analysis was performed, with treatment modality and type of SUD as main predictors, and a range of patient characteristics as covariates. Results: Patients (N=319) were diagnosed with AUD (48%), DUD (34%), or AUD plus DUD (18%). Patients in joint treatment showed a higher prevalence of lapses during treatment than those in separate treatment (26% versus 12%; p=0.009), but there was no significant difference in the prevalence of premature terminations (38% versus 44%, p=0.26). Treatment modality and interaction between modality and type of SUD was not significantly associated with premature termination. Joint treatment completers showed higher satisfaction with treatment than separate treatment completers ( p<0.001). Conclusion: We found no evidence here for a difference between treatment modalities in terms of premature termination rate. Satisfaction level was higher in those who completed joint treatment compared to separate treatment.Peer reviewe
An alternative to the conventional micro-canonical ensemble
Usual approach to the foundations of quantum statistical physics is based on
conventional micro-canonical ensemble as a starting point for deriving
Boltzmann-Gibbs (BG) equilibrium. It leaves, however, a number of conceptual
and practical questions unanswered. Here we discuss these questions, thereby
motivating the study of a natural alternative known as Quantum Micro-Canonical
(QMC) ensemble. We present a detailed numerical study of the properties of the
QMC ensemble for finite quantum systems revealing a good agreement with the
existing analytical results for large quantum systems. We also propose the way
to introduce analytical corrections accounting for finite-size effects. With
the above corrections, the agreement between the analytical and the numerical
results becomes very accurate. The QMC ensemble leads to an unconventional kind
of equilibrium, which may be realizable after strong perturbations in small
isolated quantum systems having large number of levels. We demonstrate that the
variance of energy fluctuations can be used to discriminate the QMC equilibrium
from the BG equilibrium. We further suggest that the reason, why BG equilibrium
commonly occurs in nature rather than the QMC-type equilibrium, has something
to do with the notion of quantum collapse.Comment: 25 pages, 6 figure
Comment to: "A note on failure of the ladder approximation to QCD" [Phys. Lett. B 640 (2006) 196 ]
In the paper [Hong-Shi Zong, Wei-Min Sun, Phys. Lett. B 640 (2006) 196], the
authors claim that our proof of the inconsistency of the ladder approximation
to QCD [Phys. Lett. B 611 (2005) 129] was incorrect. However, their claim is
based on a derivation which contains a rough mathematical mistake, namely the
unjustified change of variables in the divergent (though regularized)
integrals. In this comment I will show this explicitly, so our conclusion that
the ladder approximation to QCD is inconsistent remains, of course, correct.Comment: 2 pages, no figure, no table
Spectral Speckle Customization
Speckle patterns are used in a broad range of applications including
microscopy, imaging, and light-matter interactions. Tailoring speckles'
statistics can dramatically enhance their performance in applications. We
present an experimental technique for customizing the spatio-spectral speckled
intensity statistics of optical pulses at the output of a complex medium (a
disordered multimode fiber) by controlling the spatial profile of the input
light. We demonstrate that it is possible to create ensembles of independent
speckle patterns with arbitrary statistics at a single wavelength,
simultaneously at decorrelated wavelengths, and even tailored statistics across
an entire pulse spectrum
Density Dependence of Nucleon Bag Constant, Radius and Mass in an Effective Field Theory Model of QCD
With the global color symmetry model (GCM) being extended to finite chemical
potential, the density dependence of the bag constant, the total energy and the
radius of a nucleon, as well as the quark condensate in nuclear matter are
investigated. A maximal nuclear matter density for the existence of the bag
with three quarks confined within is obtained. The calculated results indicate
that, before the maximal density is reached, the bag constant, the total energy
of a nucleon and the quark condensate decrease gradually, and the radius of a
nucleon increases, with the increasing of the nuclear matter density.
Nevertheless no sudden change emerges. As the maximal nuclear matter density is
reached, a phase transition from nucleons to quarks takes place and the chiral
symmetry is restored.Comment: Latex, 15 postscript pages, 6 postscript files, To be published in
Nuclear Physics
Infrared Behaviour of Propagators and Vertices
We elucidate constraints imposed by confinement and dynamical chiral symmetry
breaking on the infrared behaviour of the dressed-quark and -gluon propagators,
and dressed-quark-gluon vertex. In covariant gauges the dressing of the gluon
propagator is completely specified by P(k^2):= 1/[1+Pi(k^2)], where Pi(k^2) is
the vacuum polarisation. In the absence of particle-like singularities in the
dressed-quark-gluon vertex, extant proposals for the dressed-gluon propagator
that manifest P(k^2=0)=0 and Max[P(k^2)]~10 neither confine quarks nor break
chiral symmetry dynamically. This class includes all existing estimates of
P(k^2) via numerical simulations.Comment: 10 pages, 2 figure
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