Quantum Gowdy T3T^3 Model: Schrodinger Representation with Unitary Dynamics

The linearly polarized Gowdy $T^3$ model is paradigmatic for studying technical and conceptual issues in the quest for a quantum theory of gravity since, after a suitable and almost complete gauge fixing, it becomes an exactly soluble midisuperspace model. Recently, a new quantization of the model, possessing desired features such as a unitary implementation of the gauge group and of the time evolution, has been put forward and proven to be essentially unique. An appropriate setting for making contact with other approaches to canonical quantum gravity is provided by the Schr\"odinger representation, where states are functionals on the configuration space of the theory. Here we construct this functional description, analyze the time evolution in this context and show that it is also unitary when restricted to physical states, i.e. states which are solutions to the remaining constraint of the theory.Comment: 21 pages, version accepted for publication in Physical Review

Regression with Linear Factored Functions

Many applications that use empirically estimated functions face a curse of dimensionality, because the integrals over most function classes must be approximated by sampling. This paper introduces a novel regression-algorithm that learns linear factored functions (LFF). This class of functions has structural properties that allow to analytically solve certain integrals and to calculate point-wise products. Applications like belief propagation and reinforcement learning can exploit these properties to break the curse and speed up computation. We derive a regularized greedy optimization scheme, that learns factored basis functions during training. The novel regression algorithm performs competitively to Gaussian processes on benchmark tasks, and the learned LFF functions are with 4-9 factored basis functions on average very compact.Comment: Under review as conference paper at ECML/PKDD 201

A study of atmospheric neutrinos with the IMB detector

A sample of 401 contained neutrino interactions collected in the 3300 metric ton fiducial mass IMB detector was used to study neutrino oscillations, geomagnetic modulation of the flux and to search for point sources. The majority of these events are attributed to neutrino interactions. For the most part, these neutrinos are believed to originate as tertiary products of cosmic ray interactions in the atmosphere. The neutrinos are a mixture of v sub e and v sub micron

On the General Analytical Solution of the Kinematic Cosserat Equations

Based on a Lie symmetry analysis, we construct a closed form solution to the kinematic part of the (partial differential) Cosserat equations describing the mechanical behavior of elastic rods. The solution depends on two arbitrary analytical vector functions and is analytical everywhere except a certain domain of the independent variables in which one of the arbitrary vector functions satisfies a simple explicitly given algebraic relation. As our main theoretical result, in addition to the construction of the solution, we proof its generality. Based on this observation, a hybrid semi-analytical solver for highly viscous two-way coupled fluid-rod problems is developed which allows for the interactive high-fidelity simulations of flagellated microswimmers as a result of a substantial reduction of the numerical stiffness.Comment: 14 pages, 3 figure

Quantum Gowdy T3T^3 model: A unitary description

The quantization of the family of linearly polarized Gowdy $T^3$ spacetimes is discussed in detail, starting with a canonical analysis in which the true degrees of freedom are described by a scalar field that satisfies a Klein-Gordon type equation in a fiducial time dependent background. A time dependent canonical transformation, which amounts to a change of the basic (scalar) field of the model, brings the system to a description in terms of a Klein-Gordon equation on a background that is now static, although subject to a time dependent potential. The system is quantized by means of a natural choice of annihilation and creation operators. The quantum time evolution is considered and shown to be unitary, allowing both the Schr\"odinger and Heisenberg pictures to be consistently constructed. This has to be contrasted with previous treatments for which time evolution failed to be implementable as a unitary transformation. Possible implications for both canonical quantum gravity and quantum field theory in curved spacetime are commented

Localization of a 64-kDa phosphoprotein in the lumen between the outer and inner envelopes of pea chloroplasts

The identification and localization of a marker protein for the intermembrane space between the outer and inner chloroplast envelopes is described. This 64-kDa protein is very rapidly labeled by [γ-32P]ATP at very low (30 nM) ATP concentrations and the phosphoryl group exhibits a high turnover rate. It was possible to establish the presence of the 64-kDa protein in this plastid compartment by using different chloroplast envelope separation and isolation techniques. In addition comparison of labeling kinetics by intact and hypotonically lysed pea chloroplasts support the localization of the 64-kDa protein in the intermembrane space. The 64-kDa protein was present and could be labeled in mixed envelope membranes isolated from hypotonically lysed plastids. Mixed envelope membranes incorporated high amounts of 32P from [γ-32P]ATP into the 64-kDa protein, whereas separated outer and inner envelope membranes did not show significant phosphorylation of this protein. Water/Triton X-114 phase partitioning demonstrated that the 64-kDa protein is a hydrophilic polypeptide. These findings suggest that the 64-kDa protein is a soluble protein trapped in the space between the inner and outer envelope membranes. After sonication of mixed envelope membranes, the 64-kDa protein was no longer present in the membrane fraction, but could be found in the supernatant after a 110000 × g centrifugation

Holography in asymptotically flat space-times and the BMS group

In a previous paper (hep-th/0306142) we have started to explore the holographic principle in the case of asymptotically flat space-times and analyzed in particular different aspects of the Bondi-Metzner-Sachs (BMS) group, namely the asymptotic symmetry group of any asymptotically flat space-time. We continue this investigation in this paper. Having in mind a S-matrix approach with future and past null infinity playing the role of holographic screens on which the BMS group acts, we connect the IR sectors of the gravitational field with the representation theory of the BMS group. We analyze the (complicated) mapping between bulk and boundary symmetries pointing out differences with respect to the AdS/CFT set up. Finally we construct a BMS phase space and a free hamiltonian for fields transforming w.r.t BMS representations. The last step is supposed to be an explorative investigation of the boundary data living on the degenerate null manifold at infinity.Comment: 31 pages, several changes in section 3 and 7 and references update

Análise de agrupamento de municípios do entorno do Lago de Sobradinho, utilizando atributos físicos do solo.

Objetivou-se avaliar os atributos físicos do solo dos municípios localizados no entorno do lago de Sobradinho utilizando a análise de agrupamento. Foram coletadas amostras de solo nas camadas de 0-0,10 m, com três repetições em cada propriedade, sendo o uso do solo a caatinga e a agricultura nos municípios de Sobradinho em quatro propriedades, Casa Nova com oito propriedades, Sento Sé com oito propriedades e Remanso com quatro propriedades no Estado da Bahia. Os atributos analisadas foram: diâmetro médio ponderado (DMP), diâmetro médio geométrico (DMG), densidade do solo (Ds), porosidade total do solo (Pt), argila, silte, areia, grau de floculação (GF) e argila dispersa em água (ADA), sendo analisados pela análise de agrupamento utilizando o método de Ward e a distância Euclidiana, após a estatística descritiva e o teste de normalidade. Verificou-se a formação clara de dois grandes grupos: no qual GI engloba Casa Nova e Remanso e o GII formado por Sento Sé e Sobradinho. Dentro do GII podem diferir outros dois subgrupos tendo Casa Nova e Remanso em um deles e isoladamente Sobradinho. A formação do GII pode ser atribuída aos maiores valores de argila e consequentemente do grau de floculação. De modo geral, não se verifica diferença entre o uso da agricultura e a Caatinga, em todos os grupos, com bases nos atributos físicos do solo

Análise multivariada da qualidade química de um Latossolo sob sistemas de manejo do solo.

Os sistemas de manejo podem influenciar atributos químicos do solo, sendo importante a busca de aplicação de novas técnicas para a compreensão dos efeitos ocasionados. Objetivou-se avaliar atributos químicos de um Latossolo Vermelho distroférrico sob sistemas de manejo por meio da estatística multivariada. Os tratamentos consistiram dos seguintes sistemas de manejo do solo: plantio direto, plantio direto escarificado, plantio direto escarificado cruzado, preparo convencional, preparo reduzido e preparo conservacionista. O trabalho foi conduzido com delineamento em blocos ao acaso com quatro repetições, sendo as amostras coletadas nas camadas de 0,00-0,10 e 0,10-0,20 m. Os atributos analisados foram: pH em água; matéria orgânica; cálcio, magnésio, potássio e alumínio trocáveis; fósforo e acidez potencial, com posterior cálculo da soma de bases, da capacidade de troca de cátions a pH 7,0 e da saturação por bases. Os dados foram analisados por meio de agrupamentos e componentes principais. Verificou-se que o sistema de preparo convencional e plantio direto na camada de 0,00 - 0,10 m apresentaram similaridade, e que preparo reduzido e plantio direto escarificado cruzado comparado aos demais sistemas, concentraram o maior número de atributos químicos e foram influenciados pelos valores de cálcio, magnésio, soma de base, capacidade de troca de cátions e saturação por base. Na camada de 0,10-0,20 m, os subgrupos plantio direto escarificado cruzado, preparo convencional, preparo reduzido e plantio direito concentraram grande parte dos atributos químicos, sendo influenciado pelos valores de potássio, soma de base, magnésio, capacidade de troca de cátions, saturação por base, matéria orgânica e pH