Unpolarized light in quantum optics

We present a new derivation of the unpolarized quantum states of light, whose general form was first derived by Prakash and Chandra [Phys. Rev. A 4, 796 (1971)]. Our derivation makes use of some basic group theory, is straightforward, and offers some new insights.Comment: 3 pages, REVTeX, presented at ICQO'200

Adiabatic decaying vacuum model for the universe

We study a model that the entropy per particle in the universe is constant. The sources for the entropy are the particle creation and a lambda decaying term. We find exact solutions for the Einstein field equations and show the compatibilty of the model with respect to the age and the acceleration of the universe.Comment: 10 pages, 2 figure

Movimento e área de uso do jacaré-do-pantanal.

O estudo dos padrões de movimento dos jacarés do Pantanal ocorreu em uma área de lagos isolados e em uma área cortada por rios intermitentes no Pantanal. Foram marcados jacarés em 100 lagos, na área de lagos (1986-2001), e em 2 rios, na área de rios (1987-1999), recapturados 163 machos adultos, 132 fêmeas adultas e 237 jovens e monitorados 67 jacarés adultos por radiotelemetria nas duas áreas. No intervalo de 2 anos, a maioria dos jovens moveram-se apenas dentro da área de lagos ou da de rios, numa distância máxima de 6,0 km (x = 0,5; DP = 1,0 km), na área de lagos, e de 1,25 km (x= 0,6; DP = 0,3 km), na área de rios. Somente cinco jovens marcados nos lagos foram recapturados depois de um intervalo de 5 a 10 anos. Um jovem permaneceu na área de lago e quatro saíram para a de rio. Em 1 ano, fêmeas e machos com mais que 40 cm de comprimento rostro-cloacal (CRC) moveram-se em distâncias similares nas duas áreas (até 9,8 km). Fêmeas e machos maiores que 40 cm (CRC) foram registrados locomovendo-se por distâncias máximas de 16 a 18 km, respectivamente, em períodos de 1 a 5 anos. Caçadores mataram sete machos que saíram da área de lagos para os de rios. As distâncias percorridas pelos machos e fêmeas maiores que 40 cm (CRC) tiveram a influência do intervalo entre as capturas e do nível médio da água. Os jacarés com radiotransmissores moveram-se por até 3 km em 40 dias. Uma fêmea reprodutiva distanciou 5 km da área de rio onde foi marcada, indo para um local onde nidificou no período de 60 dias. O espaço usado em um período de 7 meses, não variou entre as duas áreas, mas os jacarés maiores se movimentaram sobre áreas mais extensas. O tamanho da área de uso dos indivíduos com rádios, em períodos de 15 a 447 dias, oscilou de 2 a 1649 ha e relacionou-se com o tempo de rastreamento e o comprimento dos jacarés na área de rios. As áreas usadas pelos 5 machos em locais sujeitos à caça experimental foram similares das usadas, pelos outros 5 machos em locais não-sujeitos à caça. Pode-se dizer que o movimento extensivo dos jacarés, a longo e curto prazo, de que fazendas individuais não poderiam ser consideradas unidades de manejo para o uso sustentado no Pantanal.bitstream/item/37300/1/BP57.pd

The consolidation and effectiveness of matrix support in mental health in Brazil - bottlenecks and challenges

Passados dez anos da implementação do apoio matricial nas redes de saúde por meio dos Núcleos de Apoio à Saúde da Família, ainda sente-se a falta de dados consistentes quanto à consolidação e efetividade desse arranjo. Nesse sentido, este estudo teve como objetivo revisar a bibliografia nacional dos últimos dez anos a fim de identificar os impasses e desafios vivenciados no apoio matricial em saúde mental na Atenção Primária, classificando-os a partir de uma reconstrução teórico-conceitual e fazendo uma articulação destes com os desafios pontuados em congêneres internacionais do apoio matricial. Entre os principais pontos levantados pelo estudo, destacou-se a necessidade de delineamentos claros para prática de matriciamento; investimento maciço em formação e capacitação dos profissionais; e criação de espaços institucionalizados com encontros sistemáticos dos profissionais para discussão dos casos e avaliação conjunta do andamento das atividades23COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESsem informaçãoTen years on from the introduction of matrix support in health networks through the creation of Family Health Support Centers, there is still a lack of consistent data to measure the success of consolidation and effectiveness of this arrangement. With this in mind, we conducted a literature review of national articles produced over the last ten years to identify the bottlenecks and challenges faced by matrix support in mental health in Primary Care. The problems were classified using a theoretical and conceptual reconstruction and drawing on similar experiences with matrix support in other countries. The following key points emerged from the review: the need to provide clear guidelines for matrix support; the need for major investment in training and capacity building; and the need to create institutionalized spaces to foster systematic communication between professionals to discuss cases and promote joint evaluation of the progress of activitie

String windings in the early universe

We study string dynamics in the early universe. Our motivation is the proposal of Brandenberger and Vafa, that string winding modes may play a key role in decompactifying three spatial dimensions. We model the universe as a homogeneous but anisotropic 9-torus filled with a gas of excited strings. We adopt initial conditions which fix the dilaton and the volume of the torus, but otherwise assume all states are equally likely. We study the evolution of the system both analytically and numerically to determine the late-time behavior. We find that, although dynamical evolution can indeed lead to three large spatial dimensions, such an outcome is not statistically favored.Comment: 26 pages, LaTeX, 4 eps figure

Gravitational Lorentz Force and the Description of the Gravitational Interaction

In the context of a gauge theory for the translation group, we have obtained, for a spinless particle, a gravitational analog of the Lorentz force. Then, we have shown that this force equation can be rewritten in terms of magnitudes related to either the teleparallel or the riemannian structures induced in spacetime by the presence of the gravitational field. In the first case, it gives a force equation, with torsion playing the role of force. In the second, it gives the usual geodesic equation of General Relativity. The main conclusion is that scalar matter is able to feel anyone of the above spacetime geometries, the teleparallel and the metric ones. Furthermore, both descriptions are found to be completely equivalent in the sense that they give the same physical trajectory for a spinless particle in a gravitational field.Comment: Equations (44)-(47) correcte

Black Hole Formation with an Interacting Vacuum Energy Density

We discuss the gravitational collapse of a spherically symmetric massive core of a star in which the fluid component is interacting with a growing vacuum energy density. The influence of the variable vacuum in the collapsing core is quantified by a phenomenological \beta-parameter as predicted by dimensional arguments and the renormalization group approach. For all reasonable values of this free parameter, we find that the vacuum energy density increases the collapsing time but it cannot prevent the formation of a singular point. However, the nature of the singularity depends on the values of \beta. In the radiation case, a trapped surface is formed for \beta<1/2 whereas for \beta>1/2, a naked singularity is developed. In general, the critical value is \beta=1-2/3(1+\omega), where the \omega-parameter describes the equation of state of the fluid component.Comment: 9 pages, 8 figure

Entanglement by linear SU(2) transformations: generation and evolution of quantum vortex states

We consider the evolution of a two-mode system of bosons under the action of a Hamiltonian that generates linear SU(2) transformations. The Hamiltonian is generic in that it represents a host of entanglement mechanisms, which can thus be treated in a unified way. We start by solving the quantum dynamics analytically when the system is initially in a Fock state. We show how the two modes get entangled by evolution to produce a coherent superposition of vortex states in general, and a single vortex state under certain conditions. The degree of entanglement between the modes is measured by finding the explicit analytical dependence of the Von Neumann entropy on the system parameters. The reduced state of each mode is analyzed by means of its correlation function and spatial coherence function. Remarkably, our analysis is shown to be equally as valid for a variety of initial states that can be prepared from a two-mode Fock state via a unitary transformation and for which the results can be obtained by mere inspection of the corresponding results for an initial Fock state. As an example, we consider a quantum vortex as the initial state and also find conditions for its revival and charge conjugation. While studying the evolution of the initial vortex state, we have encountered and explained an interesting situation in which the entropy of the system does not evolve whereas its wave function does. Although the modal concept has been used throughout the paper, it is important to note that the theory is equally applicable for a two-particle system in which each particle is represented by its bosonic creation and annihilation operators.Comment: 6 figure

Multicanonical Hybrid Monte Carlo: Boosting Simulations of Compact QED

We demonstrate that substantial progress can be achieved in the study of the phase structure of 4-dimensional compact QED by a joint use of hybrid Monte Carlo and multicanonical algorithms, through an efficient parallel implementation. This is borne out by the observation of considerable speedup of tunnelling between the metastable states, close to the phase transition, on the Wilson line. We estimate that the creation of adequate samples (with order 100 flip-flops) becomes a matter of half a year's runtime at 2 Gflops sustained performance for lattices of size up to 24^4.Comment: 15 pages, 8 figure