Low density expansion and isospin dependence of nuclear energy functional: comparison between relativistic and Skyrme models

In the present work we take the non relativistic limit of relativistic models and compare the obtained functionals with the usual Skyrme parametrization. Relativistic models with both constant couplings and with density dependent couplings are considered. While some models present very good results already at the lowest order in the density, models with non-linear terms only reproduce the energy functional if higher order terms are taken into account in the expansion.Comment: 16 pages,6 figures,5 table

Instabilities in asymmetric nuclear matter

The existence of phase transitions from liquid to gas phases in asymmetric nuclear matter (ANM) is related with the instability regions which are limited by the spinodals. In this work we investigate the instabilities in ANM described within relativistic mean field hadron models, both with constant and density dependent couplings at zero and finite temperatures. In calculating the proton and neutron chemical potentials we have used an expansion in terms of Bessel functions that is convenient at low densities. The role of the isovector scalar $\delta$-meson is also investigated in the framework of relativistic mean field models and density dependent hadronic models. It is shown that the main differences occur at finite temperature and large isospin asymmetry close to the boundary of the instability regions.Comment: 13 pages, 5 figures; to appear in Phys. Rev.

Seasonal Variation of Forage Productivity and Quality of Communally Managed Grassland in the N’Komati River Basin

Livestock production is increasing in Mozambique. This trend, however, is facing such challenges as land tenure, erratic and not well-distributed rainfall (resulting in floods or droughts), overgrazing, wildfires, and the unsustainable resource management practices of communities. The study objectives were to evaluate forage species occurrence and seasonal variation and to estimate grassland productivity, nutritive value and savanna carrying capacity

Density Dependent Parametrization Models: Formalism and Applications

In this work we derive a formalism to incorporate asymmetry and temperature effects in the Brown-Rho (BR) scaled lagrangian model in a mean field theory. The lagrangian density discussed in this work requires less parameters than the usual models with density dependent couplings. We also present the formalism with the inclusion of the eight lightest baryons, two lightest leptons, beta equilibrium and charge neutrality in order to apply the BR scaled model to the study of neutron stars. The results are again compared with the ones obtained from another density dependent parametrization model. The role played by the rearrangement term at T=0 for nuclear or neutron star matter and at finite temperature is investigated. The BR scaled model is shown to be a good tool in studies involving density dependent effective masses and in astrophysics applications.Comment: 23 pages, 10 figure

The Rarita-Schwinger Particles Under de Influence of Strong Magnetic Fields

In this work, we calculate the solutions of the Rarita-Schwinger equation with the inclusion of the eletromagnetic interaction. Our gauge and coupling prescription choices lead to Dirac-type solutions. One of the consequences of our results are the Landau level occupation of particles, quite different from the usual spin 1/2 particle system occupation numbers.Comment: 12 page

Detrended Fluctuation Analysis of Systolic Blood Pressure Control Loop

We use detrended fluctuation analysis (DFA) to study the dynamics of blood pressure oscillations and its feedback control in rats by analyzing systolic pressure time series before and after a surgical procedure that interrupts its control loop. We found, for each situation, a crossover between two scaling regions characterized by exponents that reflect the nature of the feedback control and its range of operation. In addition, we found evidences of adaptation in the dynamics of blood pressure regulation a few days after surgical disruption of its main feedback circuit. Based on the paradigm of antagonistic, bipartite (vagal and sympathetic) action of the central nerve system, we propose a simple model for pressure homeostasis as the balance between two nonlinear opposing forces, successfully reproducing the crossover observed in the DFA of actual pressure signals

Controlled coupling of counterpropagating whispering-gallery modes by a single Rayleigh scatterer: a classical problem in a quantum optical light

We present experiments where a single subwavelength scatterer is used to examine and control the back-scattering induced coupling between counterpropagating high-Q modes of a microsphere resonator. Our measurements reveal the standing wave character of the resulting symmetric and antisymmetric eigenmodes, their unbalanced intensity distributions, and the coherent nature of their coupling. We discuss our findings and the underlying classical physics in the framework common to quantum optics and provide a particularly intuitive explanation of the central processes.Comment: accepted for publication in Pysical Review Letter

The pasta phase within density dependent hadronic models

In the present paper we investigate the onset of the pasta phase with different parametrisations of the density dependent hadronic model and compare the results with one of the usual parametrisation of the non-linear Walecka model. The influence of the scalar-isovector virtual delta meson is shown. At zero temperature two different methods are used, one based on coexistent phases and the other on the Thomas-Fermi approximation. At finite temperature only the coexistence phases method is used. npe matter with fixed proton fractions and in beta-equilibrium are studied. We compare our results with restrictions imposed on the the values of the density and pressure at the inner edge of the crust, obtained from observations of the Vela pulsar and recent isospin diffusion data from heavy-ion reactions, and with predictions from spinodal calculations.Comment: 15 pages, 11 figures and 7 table

Dynamics of domain wall networks with junctions

We use a combination of analytic tools and an extensive set of the largest and most accurate three-dimensional field theory numerical simulations to study the dynamics of domain wall networks with junctions. We build upon our previous work and consider a class of models which, in the limit of large number $N$ of coupled scalar fields, approaches the so-called `ideal' model (in terms of its potential to lead to network frustration). We consider values of $N$ between N=2 and N=20, and a range of cosmological epochs, and we also compare this class of models with other toy models used in the past. In all cases we find compelling evidence for a gradual approach to scaling, strongly supporting our no-frustration conjecture. We also discuss the various possible types of junctions (including cases where there is a hierarchy of them) and their roles in the dynamics of the network. Finally, we revise the Zel'dovich bound and provide an updated cosmological bound on the energy scale of this type of defect network: it must be lower than $10 {\rm keV}$.Comment: Submitted to Phys. Rev.