Light Clusters and Pasta Phases in Warm and Dense Nuclear Matter

The pasta phases are calculated for warm stellar matter in a framework of relativistic mean-field models, including the possibility of light cluster formation. Results from three different semiclassical approaches are compared with a quantum statistical calculation. Light clusters are considered as point-like particles, and their abundances are determined from the minimization of the free energy. The couplings of the light-clusters to mesons are determined from experimental chemical equilibrium constants and many-body quantum statistical calculations. The effect of these light clusters on the chemical potentials is also discussed. It is shown that including heavy clusters, light clusters are present until larger nucleonic densities, although with smaller mass fractions.Comment: 15 pages, 13 figures, accepted for publication in Physical review

Dynamical properties of nuclear and stellar matter and the symmetry energy

The effects of density dependence of the symmetry energy on the collective modes and dynamical instabilities of cold and warm nuclear and stellar matter are studied in the framework of relativistic mean-field hadron models. The existence of the collective isovector and possibly an isoscalar collective mode above saturation density is discussed. It is shown that soft equations of state do not allow for a high density isoscalar collective mode, however, if the symmetry energy is hard enough an isovector mode will not disappear at high densities. The crust-core transition density and pressure are obtained as a function of temperature for $\beta$-equilibrium matter with and without neutrino trapping. An estimation of the size of the clusters formed in the non-homogeneous phase as well as the corresponding growth rates and distillation effect is made. It is shown that cluster sizes increase with temperature, that the distillation effect close to the inner edge of the crust-core transition is very sensitive to the symmetry energy, and that, within a dynamical instability calculation, the pasta phase exists in warm compact stars up to 10 - 12 MeV.Comment: 16 pages, 10 figures. Submitted for publication in Phys. Rev.

Heavy baryons in hot stellar matter with light nuclei and hypernuclei

The production of light nuclei and hypernuclei together with heavy baryons, both hyperons and $\Delta$-baryons, in low density matter as found in stellar environments such as supernova or binary mergers is studied within relativistic mean-field models. Five light nuclei were considered together with three light hypernuclei. The presence of both hyperons and $\Delta$-baryons shift the dissolution of clusters to larger densities and increase the abundance of clusters. This effect is larger the smaller the charge fraction and the higher the temperature. The couplings of the $\Delta$-baryons were chosen imposing that the nucleon effective mass remains finite inside neutron stars.Comment: 11 pages, 8 figures, submitted to Phys. Rev.

Unified neutron star equations of state calibrated to nuclear properties

Recently, in Malik23, a dataset of several EoS for purely nucleonic stellar matter based on a non-linear RMF model prescription, and constrained to properties of nuclear matter, to state-of-the-art chiral effective field theory calculations for low-density neutron matter, and to astrophysical data, were proposed. In this work, twenty one unified neutron star EoS were chosen from that dataset, in such a way that a large range of values of the slope of the symmetry energy at saturation is covered. Several quantities are calculated and discussed, such as the the proton fraction and the direct Urca behavior, the density dependence of the speed of sound and the trace anomaly, the crust-core transition properties, the compatibility with astrophysical observations, and the neutron matter properties from $\chi$EFT calculations and pQCD constraints. We construct unified EoS, where the outer crust is given by the BSk22 functional, and the inner crust is calculated from a CLD approximation. The core is purely nucleonic, made of protons, neutrons, electrons and muons, under charge neutrality and in $\beta-$equilibrium conditions. The correlation of the slope of the symmetry energy at saturation with the crust-core transition density and proton fraction is analysed, and equations that translate these relations are proposed. Moreover, the spectral representation for all the EOS according to the format proposed in Lindblom10 is given, which is a convenient representation to study quasi-periodic oscillations with realistic EOS. It is shown that several of these EoS have in the center of the most massive NS a speed of sound squared of the order of $\lesssim 0.5$. Most of the EoS predict a maximum central density of the order of about 6 times the nuclear saturation density. Three of the EoS satisfy all of the constraints imposed. All these EoS will be made available in the CompOSE platform.Comment: 14 pages, 12 figures, 7 table

Three Dimensional Equation of State for Core-Collapse Supernova Matter

The core-collapse supernova (CCSN) phenomenon, one of the most explosive events in the Universe, presents a challenge to theoretical astrophysics. Stellar matter in supernovae, experiencing most extreme pressure and temperature, undergoes transformations that cannot be simulated in terrestrial laboratories. Construction of astrophysical models is the only way towards comprehension of CCSN. The key microscopic input into CCSN models is the Equation of State (EoS), connecting the pressure of stellar matter to the energy density and temperature, dependent upon its composition. Of the large variety of forms of CCSN matter, we focus on the transitional region between homogeneous and inhomogeneous phases. Here the nuclear structures undergo a series of changes in shape from spherical to exotic deformed forms: rods, slabs, cylindrical holes and bubbles, termed “nuclear pasta”. We perform a three-dimensional, finite temperature Skyrme-Hartree-Fock + BCS (3D-SHF) study of the inhomogeneous nuclear matter, where we calculate self-consistently the nuclear pasta phase and determine the phase transition between pasta and uniform matter and its character. As the nuclear matter properties depend on the effective nucleon-nucleon interaction in the 3D-SHF model, we employ four different parametrizations of the Skyrme interaction, SkM*, SLy4, NRAPR and SQMC700. For each of these interactions we calculate free energy, pressure, entropy and chemical potentials in the space of particle number densities, temperatures and proton fractions, expected to cover the pasta region. The available data analysed are for particle number densities 0.02 - 0.12 fm−3 [reciprocal of cubic fermi], temperatures 0 - 10 MeV and a proton fraction equal to 0.3. The data indicate a distinct discontinuity in the first derivatives of the free energy, which can be interpreted as a fingerprint of the first order transition between inhomogeneous and homogeneous supernova matter. This transition occurs naturally in our model, without a need for thermodynamic constructions. However, the transitions between distinct pasta formations are much less pronounced and hard to detect with certainty

Caracterização de dermatófitos isolados de ouriço-cacheiro em Portugal

Dermatofitoses ou tinea são infeções fúngicas dos tecidos queratinizados do ser humano e de animais, causadas por um grupo de fungos específicos, denominados de dermatófitos. Os dermatófitos estão agrupados em três géneros: Trichophyton, Microsporum e Epidermophyton. Os ouriços-cacheiros são consumidores primários e dispersores de sementes ou predadores de grande quantidade e diversidade de invertebrados e possuem uma grande distribuição geográfica. Este estudo teve por objetivo isolar e caracterizar dermatófitos de ouriço-cacheiro com sintomas, queda dos espinhos e feridas principalmente na região da cabeça. As amostras recolhidas de animais doentes foram inoculadas em meio Agar Sabouraud Dextrose e Agar de Extrato de Malte para isolamento de fungos. Os isolados obtidos foram identificados por sequenciação da região ITS (internal transcribed spacer) do cluster de RNA ribossomal e, quando necessário, de outras regiões, tal como parte do gene que codifica para a beta-tubulina (tub2). Os isolados foram ainda caracterizados quanto à sua micromorfologia, bem como a capacidade de crescimento e produção de atividades enzimáticas extracelulares (lipase, gelatinase e protease) a 25º C, 30º C e 37º C. Foram identificadas três espécies de fungos, duas pertencentes ao género Trichophyton, T. interdigitale e Trichophyton sp., e uma pertencente ao género Aspergillus, A. terreus. Trichophyton sp. é filogeneticamente próximo de T. erinacei, mas poderá representar uma nova espécie. No entanto, são necessários estudos adicionais para confirmar esta hipótese. Os isolados de Trichophyton cresceram melhor a 30º C e os de Aspergillus a 37º C. Foi detetada atividade enzimática nas espécies estudadas, sendo notado um efeito da temperatura. Aspergillus terreus não produziu gelatinase a 30 e 37º C enquanto T. interdigitale não produziu protease a 37º C. Serão necessários estudos futuros para uma caracterização mais detalhada da diversidade de dermatófitos presentes em ouriço-cacheiro em Portugal.Dermatophytoses or tinea are fungal infections of the keratinized tissues of humans and animals, caused by a group of specific fungi, called dermatophytes. Dermatophytes are grouped into three genera: Trichophyton, Microsporum and Epidermophyton. Hedgehogs are primary consumers and seed dispersers or predators of large numbers and diversity of invertebrates and have a wide geographic distribution. The objective of this study was to isolate and characterize hedgehog dermatophytes with symptoms, fall of spines and wounds, mainly in the head region. Samples collected from sick animals were inoculated on Sabouraud Dextrose Agar and Malt Extract Agar for fungal isolation. The isolates obtained were identified by sequencing the ITS (internal transcribed spacer) region of the ribosomal RNA cluster and, when necessary, other regions, such as part of the gene encoding beta-tubulin (tub2). The isolates were further characterized in terms of their micromorphology, as well as their capacity for growth and production of extracellular enzymatic activities (lipase, gelatinase and protease) at 25º C, 30º C and 37º C. Three species of fungi were identified, 2 belonging to the genus Trichophyton, T. interdigitale and Trichophyton sp., and one belonging to the genus Aspergillus, A. terreus. Trichophyton sp. is phylogenetically close to T. erinacei, but may represent a new species. However, further studies are needed to confirm this hypothesis. Trichophyton isolates grew better at 30º C and Aspergillus isolates at 37º C. Enzymatic activity was detected in the studied species, with an effect of temperature being noted. Aspergillus terreus did not produce gelatinase at 30 and 37º C while T. interdigitale did not produce protease at 37º C. Future studies will be needed for a more detailed characterization of the diversity of dermatophytes present in hedgehogs in Portugal.Mestrado em Microbiologi