Pentaquarks in the medium in the quark-meson coupling model

We calculate the properties of the pentaquarks $\Theta^+$ and $\Xi^{--,0}$ in symmetric nuclear matter using the quark meson coupling model (QMC). The stability of the $\Theta^+$ in the medium with respect to the channel $\Theta^+\to NK^+$ is discussed.Comment: 6 pages, 5 figures, revte

Searching for the dual of the Maxwell-Chern-Simons model minimally coupled to dynamical U(1) charged matter

The possibility of dual equivalence between the self-dual and the Maxwell-Chern-Simons (MCS) models when the latter is coupled to dynamical, U(1) fermionic charged matter is examined. The proper coupling in the self-dual model is then disclosed using the iterative gauge embedding approach. We found that the self-dual potential needs to couple directly to the Chern-Kernel of the source in order to establish this equivalence besides the need for a self-interaction term to render the matter sector unchanged.Comment: 4 pages, RevTeX, new references, accepted for publication on Phys. Lett.

First-order transition in small-world networks

The small-world transition is a first-order transition at zero density $p$ of shortcuts, whereby the normalized shortest-path distance undergoes a discontinuity in the thermodynamic limit. On finite systems the apparent transition is shifted by $\Delta p \sim L^{-d}$. Equivalently a ``persistence size'' $L^* \sim p^{-1/d}$ can be defined in connection with finite-size effects. Assuming $L^* \sim p^{-\tau}$, simple rescaling arguments imply that $\tau=1/d$. We confirm this result by extensive numerical simulation in one to four dimensions, and argue that $\tau=1/d$ implies that this transition is first-order.Comment: 4 pages, 3 figures, To appear in Europhysics Letter

Evolution of the fine-structure constant in the non-linear regime

We study the evolution of the fine-structure constant, $\alpha$, induced by non-linear density perturbations in the context of the simplest class of quintessence models with a non-minimal coupling to the electromagnetic field, in which the two available free functions (potential and gauge kinetic function) are Taylor-expanded up to linear order. We show that the results obtained using the spherical infall model for an infinite wavelength inhomogeneity are inconsistent with the results of a local linearized gravity study and we argue in favour of the second approach. We also discuss recent claims that the value of $\alpha$ inside virialised regions could be significantly different from the background one on the basis of these findings.Comment: 5 pages, 3 figure

Nuclear matter and neutron matter for improved quark mass density- dependent model with ρ\rho mesons

A new improved quark mass density-dependent model including u, d quarks, $\sigma$ mesons, $\omega$ mesons and $\rho$ mesons is presented. Employing this model, the properties of nuclear matter, neutron matter and neutron star are studied. We find that it can describe above properties successfully. The results given by the new improved quark mass density- dependent model and by the quark meson coupling model are compared.Comment: 18 pages, 7 figure

Effects of Strong Magnetic Fields on the Hadron-Quark Deconfinement Transition

The aim of the present work is to investigate the effects of strong magnetic fields on the hadron-quark phase transition point at zero temperature. To describe the hadronic phase, a relativistic mean field (RMF) model is used and to describe the quark phase a density dependent quark mass model (DDQM) is employed. As compared with the results obtained with non-magnetised matter, we observe a shift of the transition point towards higher pressures and, generally also towards higher chemical potentials. An investigation of the phase transitions that could sustain hybrid stars is also performed.Comment: 8 pages, 5 figures, 1 tabl

Desempenho de substratos na produção de mudas de alface no sistema "float" no semi-árido nordestino.

A fase de produção de mudas constitui-se na etapa mais importante dos sistemas produtivos hortícolas uma vez que o desempenho das plantas nos canteiros de produção depende dela, tanto em termos de precocidade quanto de produtividade e qualidade do produto final. O presente trabalho teve por objetivo comparar o desempenho de três substratos formulados a base de ?solo? (Argissolo) e esterco caprino na produção de mudas de alface no sistema ?float?. Avaliaram-se as características físicas, químicas e físico-químicas dos substratos e respostas biológicas das mudas. Com base nestes critérios, as melhores respostas agronômicas foram obtidas para o substrato S50EC50

Comparação de métodos de extração de nutrientes para a formulação de biofertilizantes no semi-árido nordestino.

A substituição de insumos químicos por orgânicos tem permitido, pelo menos em parte, que os esforços tecnológicos sejam direcionados a propostas agroecológicas. O presente trabalho teve por objetivo comparar dois métodos de extração de nutrientes com vistas à formulação de biofertilizantes para o cultivo de hortaliças nas pequenas propriedades do semi-árido nordestino. O método de extração Vairo dos Santos extrai uma maior quantidade de macronutrientes, enquanto o método de extração Menezes Júnior possui como prerrogativas à extração de uma maior quantidade de micronutrientes e menor extração de sódio, constituindo-se no método mais adequado às condições do semi-árido nordestino