Complete loop quantization of a dimension 1+2 Lorentzian gravity theory

De Sitter Chern-Simons gravity in D = 1 + 2 spacetime is known to possess an extension with a Barbero-Immirzi like parameter. We find a partial gauge fixing which leaves a compact residual gauge group, namely SU(2). The compacticity of the residual gauge group opens the way to the usual LQG quantization techniques. We recall the exemple of the LQG quantization of SU(2) CS theory with cylindrical space topology, which thus provides a complete LQG of a Lorentzian gravity model in 3-dimensional space-time.Comment: Loops11 - Madrid - 2011 (4 pages, Latex

Canonical Analysis of the Jackiw-Teitelboim Model in the Temporal Gauge. I. The Classical Theory

As a preparation for its quantization in the loop formalism, the 2-dimensional gravitation model of Jackiw and Teitelboim is analysed in the classical canonical formalism. The dynamics is of pure constraints as it is well-known. A partial gauge fixing of the temporal type being performed, the resulting second class constraints are sorted out and the corresponding Dirac bracket algebra is worked out. Dirac observables of this classical theory are then calculated.Comment: 15 pages, Latex. Misprint correction

Symmetries and observables in topological gravity

After a brief review of topological gravity, we present a superspace approach to this theory. This formulation allows us to recover in a natural manner various known results and to gain some insight into the precise relationship between different approaches to topological gravity. Though the main focus of our work is on the vielbein formalism, we also discuss the metric approach and its relationship with the former formalism.Comment: 34 pages; a few explanations added in subsection 2.2.1, published version of pape

The Hilbert space of Chern-Simons theory on the cylinder. A Loop Quantum Gravity approach

As a laboratory for loop quantum gravity, we consider the canonical quantization of the three-dimensional Chern-Simons theory on a noncompact space with the topology of a cylinder. Working within the loop quantization formalism, we define at the quantum level the constraints appearing in the canonical approach and completely solve them, thus constructing a gauge and diffeomorphism invariant physical Hilbert space for the theory. This space turns out to be infinite dimensional, but separable.Comment: Minor changes and some references added. Latex, 16 pages, 1 figur

Symmetries of topological field theories in the BV-framework

Topological field theories of Schwarz-type generally admit symmetries whose algebra does not close off-shell, e.g. the basic symmetries of BF models or vector supersymmetry of the gauge-fixed action for Chern-Simons theory (this symmetry being at the origin of the perturbative finiteness of the theory). We present a detailed discussion of all these symmetries within the algebraic approach to the Batalin-Vilkovisky formalism. Moreover, we discuss the general algebraic construction of topological models of both Schwarz- and Witten-type.Comment: 30 page

Familiares de Pessoas Com Sofrimento Psíquico e Profissionais de Saúde Mental: Encontros e Desencontros

As diretrizes assistenciais em saúde mental, no Brasil, prevêem o apoio à família da pessoa com sofrimento psíquico. No entanto, esses familiares referem despreparo em lidar com os encargos cotidianos da convivência com seus entes e desamparo em relação à assistência que recebem dos serviços de saúde mental. Os profissionais de saúde mental, por sua vez, enfrentam dificuldades na inclusão da família nos projetos terapêuticos e na assistência da pessoa com transtorno mental. Diante de tais fragilidades nessa relação, a proposta deste estudo foi conhecer a relação que se estabelece entre esses atores e buscar reflexão sobre fatores que interferem na possibilidade de um bom encontro entre eles. Nesse sentido, foram percorridos temas que se configuram como centrais para o conhecimento das dimensões dessa relação, como o modo de subjetivação desses sujeitos e a ética na filosofia de Espinosa. A perspectiva qualitativa de investigação configurou-se como método para alcançar os objetivos propostos. Foram realizadas entrevistas com profissionais de saúde mental de dois centros de atenção psicossocial do município de Vitória ES e com familiares de usuários destas instituições. Após análise temática do conteúdo dessas entrevistas, foram indicados e discutidos fatores de impasses a serem enfrentados nessa relação, tais como: lógica manicomial presente na relação que cada um desses sujeitos estabelecem com a loucura; dificuldade do profissional na relação com a alteridade do familiar, com prática pautada na polarização do saber, na sua moral e na retificação da dinâmica familiar; disparidade entre oferta e demanda, sem conhecimento das necessidades desses sujeitos. Familiares e profissionais não acreditam em possibilidades desse encontro e distanciam-se com suas potências de ação diminuídas. Apoiando-se na filosofia espinosana,é discutida as causas das inconveniências dessa relação e proposta a ética como possibilidade de aproximação de paixões alegres e potencia de agir dessas pessoas. Palavras-chave: ... Encargos Familiares; Práticas em Saúde; CAPS

Electrophysiological Heterogeneity of Fast-Spiking Interneurons: Chandelier versus Basket Cells

In the prefrontal cortex, parvalbumin-positive inhibitory neurons play a prominent role in the neural circuitry that subserves working memory, and alterations in these neurons contribute to the pathophysiology of schizophrenia. Two morphologically distinct classes of parvalbumin neurons that target the perisomatic region of pyramidal neurons, chandelier cells (ChCs) and basket cells (BCs), are generally thought to have the same "fast-spiking" phenotype, which is characterized by a short action potential and high frequency firing without adaptation. However, findings from studies in different species suggest that certain electrophysiological membrane properties might differ between these two cell classes. In this study, we assessed the physiological heterogeneity of fast-spiking interneurons as a function of two factors: species (macaque monkey vs. rat) and morphology (chandelier vs. basket). We showed previously that electrophysiological membrane properties of BCs differ between these two species. Here, for the first time, we report differences in ChCs membrane properties between monkey and rat. We also found that a number of membrane properties differentiate ChCs from BCs. Some of these differences were species-independent (e.g., fast and medium afterhyperpolarization, firing frequency, and depolarizing sag), whereas the differences in the first spike latency between ChCs and BCs were species-specific. Our findings indicate that different combinations of electrophysiological membrane properties distinguish ChCs from BCs in rodents and primates. Such electrophysiological differences between ChCs and BCs likely contribute to their distinctive roles in cortical circuitry in each species. © 2013 Povysheva et al

Quantization of Lorentzian 3d Gravity by Partial Gauge Fixing

D = 2+1 gravity with a cosmological constant has been shown by Bonzom and Livine to present a Barbero-Immirzi like ambiguity depending on a parameter. We make use of this fact to show that, for positive cosmological constant, the Lorentzian theory can be partially gauge fixed and reduced to an SU(2) Chern-Simons theory. We then review the already known quantization of the latter in the framework of Loop Quantization for the case of space being topogically a cylinder. We finally construct, in the same setting, a quantum observable which, although non-trivial at the quantum level, corresponds to a null classical quantity.Comment: Notation defect fixed on pages 5 (bottom) and 6 (around Eqs. 3.1)-- 19 pages, Late