98 research outputs found
Strangeness thermodynamic instabilities in hot and dense nuclear matter
We explore the presence of thermodynamic instabilities and, consequently, the realization of a pure hadronic phase transition in the hot and finite baryon density nuclear matter. The analysis is performed by means of an effective relativistic mean-field model with the inclusion of hyperons, Î-isobars, and the lightest pseudoscalar and vector meson degrees of freedom. The Gibbs conditions on the global conservation of baryon number and zero net strangeness in symmetric nuclear matter are required. Similarly to the liquidâgas phase transition, we show that a phase transition, characterized by mechanical instabilities (due to fluctuations on the baryon number) and chemical-diffusive instabilities (due to fluctuations on the strangeness number), can take place for a finite range of Î-meson coupling constants, compatible with different experimental constraints. The hadronic phase transition, which presents similar features to the quark-hadron phase transition, is characterized by different strangeness content during the mixed phase and, consequently, by a sensible variation of the strange anti-particle to particle ratios
Strangeness production at finite temperature and baryon density in an effective relativistic mean field model
We study the strangeness production in hot and dense nuclear medium, by
requiring the conservation of the baryon density, electric charge fraction and
zero net strangeness. The hadronic equation of state is investigated by means
of an effective relativistic mean field model, with the inclusion of the full
octet of baryons and kaon mesons. Kaons are considered taking into account of
an effective chemical potential depending on the self-consistent interaction
between baryons. The obtained results are compared with a minimal coupling
scheme, calculated for different values of the anti-kaon optical potential and
with non-interacting kaon particles. In this context, we also consider the
possible onset of the kaon condensation for a wide range of temperatures and
baryon densities.Comment: 13 pages, 6 figure
Quantum thermodynamic instabilities in compact stars
We study the existence of thermodynamic instabilities in the nuclear equation of state relative to the high density regime reached in the central core of compact stars. In the framework of a relativistic mean-field theory, we analyze the asymmetric nuclear properties in beta-equilibrium, including hyperons and Delta-isobar degrees of freedom. We investigate a finite density phase transition characterized by pure hadronic matter with the presence of mechanical instability (relative to the fluctuation of baryon number) and of chemical-dffusive instability (relative to the fluctuation of electric charge concentration). We find that, in the presence of thermodynamic instabilities, two hadronic phases with dfferent values of electric charge content may coexist, with several phenomenological consequences in the physics of compact stars
Chemical and mechanical instabilities in high energy heavy-ion collisions
We investigate the possible thermodynamic instability in a warm and dense nuclear medium where a phase transition from nucleonic matter to resonance-dominated Delta-matter can take place. Such a phase transition is characterized by both mechanical instability (fluctuations on the baryon density) and by chemical-diffusive instability (fuctuations onthe isospin concentration) in asymmetric nuclear matter. Similarly to the liquid-gas phase transition, the nucleonic and the Delta-matter phase have a different isospin density in the mixed phase. In the liquid-gas phase transition, the process of producing a larger neutron excess in
the gas phase is referred to as isospin fractionation. A similar effects can occur in the nucleon-Delta matter phase transition due essentially to a Delta- excess in the Delta-matter phase in asymmetric nuclear matter. In this context, we study the hadronic equation of state by means of an effective quantum relativistic mean field model with the inclusion of the full octet of baryons, the Delta-isobar
degrees of freedom, and the lightest pseudoscalar and vector mesons. Finally, we will investigate the presence of thermodynamic instabilities in a hot and dense nuclear medium where phases with different values of antibaryon-baryon ratios and strangeness content may coexist. Such a physical regime could be in principle investigated in the future high-energy compressed nuclear
matter experiments where will make it possible to create compressed baryonic matter with a high net baryon density
Nonlinear Nuclear Equation of State and Thermodynamical Instabilities in Warm and Dense Nuclear Matter
We study a nonlinear nuclear equation of state in the framework of a relativistic mean field theory. We investigate the possible thermodynamic instability in a warm and dense asymmetric nuclear medium where a phase transition from nucleonic matter to resonance dominated Î matter can take place. Such a phase transition is characterized by both mechanical instability (fluctuations on the baryon density) and by chemical-diffusive instability (fluctuations on the isospin concentration) in asymmetric nuclear matter. Similarly to the liquid-gas phase transition, the nucleonic and the Î-matter phase have a different isospin density in the mixed phase. In the liquid-gas phase transition, the process of producing a larger neutron excess in the gas phase is referred to as isospin fractionation. A similar effects can occur in the nucleon-Î matter phase transition due essentially to a negative Î-particles excess in asymmetric nuclear matter. In this context, we investigate also the effects of power law effects, due to the possible presence of nonextensive statistical mechanics effect
Power-law quantum distributions in protoneutron stars
We investigate the bulk properties of protoneutron stars in the framework of a relativistic mean field theory based on nonextensive statistical mechanics, originally proposed by C. Tsallis and characterized by power-law quantum distributions. We study the relevance of nonextensive statistical effects on the ÎČ-stable equation of state at fixed entropy per baryon, for nucleonic and hyperonic matter. We concentrate our analysis in the maximum heating and entropy per baryon s = 2 stage and T â 40 Ă· 80 MeV. This is the phase, at high temperature and high baryon density, in which the presence of nonextensive effects may alter more sensibly the thermodynamical and mechanical properties of the protoneutron star. We show that nonextensive power-law effects could play a crucial role in the structure and in the evolution of the protoneutron stars also for small deviations from the standard Boltzmann-Gibbs statistics
Nonlinear statistical effects in relativistic mean field theory
We investigate the relativistic mean field theory of nuclear matter at finite
temperature and baryon density taking into account of nonlinear statistical
effects, characterized by power-law quantum distributions. The analysis is
performed by requiring the Gibbs conditions on the global conservation of
baryon number and electric charge fraction. We show that such nonlinear
statistical effects play a crucial role in the equation of state and in the
formation of mixed phase also for small deviations from the standard
Boltzmann-Gibbs statistics.Comment: 9 pages, 5 figures. arXiv admin note: substantial text overlap with
arXiv:1005.4643 and arXiv:0912.460
Maximum likelihood drift estimation for a threshold diffusion
We study the maximum likelihood estimator of the drift parameters of a
stochastic differential equation, with both drift and diffusion coefficients
constant on the positive and negative axis, yet discontinuous at zero. This
threshold diffusion is called drifted Oscillating Brownian motion.For this
continuously observed diffusion, the maximum likelihood estimator coincide with
a quasi-likelihood estimator with constant diffusion term. We show that this
estimator is the limit, as observations become dense in time, of the
(quasi)-maximum likelihood estimator based on discrete observations. In long
time, the asymptotic behaviors of the positive and negative occupation times
rule the ones of the estimators. Differently from most known results in the
literature, we do not restrict ourselves to the ergodic framework: indeed,
depending on the signs of the drift, the process may be ergodic, transient or
null recurrent. For each regime, we establish whether or not the estimators are
consistent; if they are, we prove the convergence in long time of the properly
rescaled difference of the estimators towards a normal or mixed normal
distribution. These theoretical results are backed by numerical simulations
Kaons production at finite temperature and baryon density in an effective relativistic mean field model
We investigate the kaons production at finite temperature and baryon density
by means of an effective relativistic mean-field model with the inclusion of
the full octet of baryons. Kaons are considered taking into account of an
effective chemical potential depending on the self-consistent interaction
between baryons. The obtained results are compared with a minimal coupling
scheme, calculated for different values of the anti-kaon optical potential.Comment: 3 pages, contribution presented to the International Conference on
Exotic Atoms and Related Topic
How can we improve antidepressant adherence in the management of depression? A targeted review and 10 clinical recommendations.
Adherence to antidepressants is crucial for optimal treatment outcomes when treating depressive disorders. However, poor adherence is common among patients prescribed antidepressants. This targeted review summarizes the main factors associated with poor adherence, interventions that promote antidepressant adherence, pharmacological aspects related to antidepressant adherence, and formulates 10 clinical recommendations to optimize antidepressant adherence. Patient-related factors associated with antidepressant non-adherence include younger age, psychiatric and medical comorbidities, cognitive impairment, and substance use disorders. Prescriber behavior-related factors include neglecting medical and family histories, selecting poorly tolerated antidepressants, or complex antidepressant regimens. Multi-disciplinary interventions targeting both patient and prescriber, aimed at improving antidepressant adherence, include psychoeducation and providing the patient with clear behavioral interventions to prevent/minimize poor adherence. Regarding antidepressant choice, agents with individually tailored tolerability profile should be chosen. Ten clinical recommendations include four points focusing on the patient (therapeutic alliance, adequate history taking, measurement of depressive symptoms, and adverse effects improved access to clinical care), three focusing on prescribing practice (psychoeducation, individually tailored antidepressant choice, simplified regimen), two focusing on mental health services (improved access to mental health care, incentivized adherence promotion and monitoring), and one relating to adherence measurement (adherence measurement with scales and/or therapeutic drug monitoring)
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