A search for inverse magnetic catalysis in thermal quark-meson models

We explore the parameter space of the two-flavor thermal quark-meson model and its Polyakov loop-extended version under the influence of a constant external magnetic field $B$. We investigate the behavior of the pseudo critical temperature for chiral symmetry breaking taking into account the likely dependence of two parameters on the magnetic field: the Yukawa quark-meson coupling and the parameter $T_0$ of the Polyakov loop potential. Under the constraints that magnetic catalysis is realized at zero temperature and the chiral transition at $B=0$ is a crossover, we find that the quark-meson model leads to thermal magnetic catalysis for the whole allowed parameter space, in contrast to the present picture stemming from lattice QCD.Comment: 8 pages, 5figure

On thermal nucleation of quark matter in compact stars

The possibility of a hadron-quark phase transition in extreme astrophysical phenomena such as the collapse of a supernova is not discarded by the modern knowledge of the high-energy nuclear and quark-matter equations of state. Both the density and the temperature attainable in such extreme processes are possibly high enough to trigger a chiral phase transition. However, the time scales involved are an important issue. Even if the physical conditions for the phase transition are favorable (for a system in equilibrium), there may not be enough time for the dynamical process of phase conversion to be completed. We analyze the relevant time scales for the phase conversion via thermal nucleation of bubbles of quark matter and compare them to the typical astrophysical time scale, in order to verify the feasibility of the scenario of hadron-quark phase conversion during, for example, the core-collapse of a supernova.Comment: 6 pages, 4 figures, talk given at the International Conference SQM2009, Buzios, Rio de Janeiro, Brazil, Sep.27-Oct.2, 200

Dissipation and memory effects in pure glue deconfinement

We investigate the effects of dissipation in the deconfining transition for a pure SU(2) gauge theory. Using an effective model for the order parameter, we study its Langevin evolution numerically, and compare results from local additive noise dynamics to those obtained considering an exponential non-local kernel for early times.Comment: 4 pages, 2 figures, to appear in the proceedings of Strong and Electroweak Matter (SEWM06), BNL, May 200

Nucleation of quark matter in protoneutron star matter

The phase transition from hadronic to quark matter may take place already during the early post-bounce stage of core collapse supernovae when matter is still hot and lepton rich. If the phase transition is of first order and exhibits a barrier, the formation of the new phase occurs via the nucleation of droplets. We investigate the thermal nucleation of a quark phase in supernova matter and calculate its rate for a wide range of physical parameters. We show that the formation of the first droplet of a quark phase might be very fast and therefore the phase transition to quark matter could play an important role in the mechanism and dynamics of supernova explosions.Comment: v3: fits version published in Physical Review

NMR evidence for very slow carrier density fluctuations in the organic metal (TMTSF)2_2ClO4_4

We have investigated the origin of the large increase in spin-echo decay rates for the $^{77}$Se nuclear spins at temperatures near to $T=30K$ in the organic superconductor (TMTSF)$_2$ClO$_4$. The measured angular dependence of $T_2^{-1}$ demonstrates that the source of the spin-echo decays lies with carrier density fluctuations rather than fluctuations in TMTSF molecular orientation. The very long time scales are directly associated with the dynamics of the anion ordering occurring at $T=25K$, and the inhomogeneously broadened spectra at lower temperatures result from finite domain sizes. Our results are similar to observations of line-broadening effects associated with charge-ordering transitions in quasi-two dimensional organic conductors.Comment: 5 pages, 4 figure

Hydrodynamic Models for Heavy-Ion Collisions, and beyond

A generic property of a first-order phase transition in equilibrium, and in the limit of large entropy per unit of conserved charge, is the smallness of the isentropic speed of sound in the ``mixed phase''. A specific prediction is that this should lead to a non-isotropic momentum distribution of nucleons in the reaction plane (for energies around 40 AGeV in our model calculation). On the other hand, we show that from present effective theories for low-energy QCD one does not expect the thermal transition rate between various states of the effective potential to be much larger than the expansion rate, questioning the applicability of the idealized Maxwell/Gibbs construction. Experimental data could soon provide essential information on the dynamics of the phase transition.Comment: 10 Pages, 4 Figures. Presented at 241st WE-Heraeus Seminar: Symposium on Fundamental Issues in Elementary Matter: In Honor and Memory of Michael Danos, Bad Honnef, Germany, 25-29 Sep 200

How women’s empowerment influences fertility-related outcomes and contraceptive practices: A cross-sectional study in Mozambique

Women’s empowerment could be a crucial step for tackling gender inequality and improve women’s reproductive health and rights in Mozambique. This study aims to examine how different domains of women’s empowerment influence fertility-related outcomes and contraceptive practices in Mozambique. We used the 2015 Demographic Health Survey (DHS) conducted in Mozambique from which a sample of 2072 women aged 15 to 49 years were selected and included in this analysis. A principal component analysis was performed, and the components retained were identified as the domains of empowerment. These were: Beliefs about violence against women, Decision-making, and Control over sexuality and safe sex. A multinomial logistic regression was run to estimate the association between levels of empowerment for each domain and the study outcomes. Crude and adjusted odds ratio (OR) were calculated, with 95% confidence intervals (95% CI). Beliefs about violence against women and Control over sexuality and safe sex were positively associated with having 1 to 4 children. Control over sexuality and safe sex also increased likelihood of women wanting to space childbearing over more than 2 years. Decision-making increased the odds of women not wanting more children. Middle to high empowerment levels for Control over sexuality and safe sex also increased the chances of using any type of contraceptive method and using it for longer periods. All domains, from the middle to high levels of empowerment, decreased the chances of women not wanting to use contraception. Our study confirmed the multidimensional nature of empowerment showing that each domain had a different effect over specific fertility and contraceptive outcomes and reinforced the importance of a domain approach for estimating and understanding empowerment. It also revealed the critical role of Control over sexuality and safe sex domain for improving women’s ability to decide over fertility and contraceptive practices in Mozambique.We gratefully acknowledge the PhD grant from Fundação para a Ciência e a Tecnologia to SCL (SFRH/BD/146625/2019) and the contract to SF (CEECIND/01516/2017). We also thank the Faculty Research Committee (FRC) of the Faculty of Health Sciences of the University of Cape Town for the Post Graduate Research Training Grant (FRC Award 2019) to SCL. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript