On Unitary Time Evolution in Gowdy T3T^3 Cosmologies

A non-perturbative canonical quantization of Gowdy $T^3$ polarized models carried out recently is considered. This approach profits from the equivalence between the symmetry reduced model and 2+1 gravity coupled to a massless real scalar field. The system is partially gauge fixed and a choice of internal time is performed, for which the true degrees of freedom of the model reduce to a massless free scalar field propagating on a 2-dimensional expanding torus. It is shown that the symplectic transformation that determines the classical dynamics cannot be unitarily implemented on the corresponding Hilbert space of quantum states. The implications of this result for both quantization of fields on curved manifolds and physically relevant questions regarding the initial singularity are discussed.Comment: 16 pages, no figures, latex file; references added, a proof included. Final version to appear in IJMP

Study of the adhesion on overmoulded parts with thermoplastic/LSR combination

Multi-material parts with PBT/LSR combination were produced in two separate steps, one for the injection of PBT parts, and a second for the LSR overmoulding. The aim of this work is to study the influence of process-parameters such as mold temperature, curing time, temperature of the PBT insert before performing the overmoulding with LSR, on the adhesion with LSR’s. The effect on the adhesion of the amount of glass fiber content on the PBT was also studied. The adhesion between the materials was measured using a peel-test 90º. The results of the peel-test indicated that the adhesion is influenced by the parameters described. The adhesion between the two materials increase significantly with the increase of the processparameters

Uniqueness of the Fock representation of the Gowdy S1×S2S^1\times S^2 and S3S^3 models

After a suitable gauge fixing, the local gravitational degrees of freedom of the Gowdy $S^1\times S^2$ and $S^3$ cosmologies are encoded in an axisymmetric field on the sphere $S^2$. Recently, it has been shown that a standard field parametrization of these reduced models admits no Fock quantization with a unitary dynamics. This lack of unitarity is surpassed by a convenient redefinition of the field and the choice of an adequate complex structure. The result is a Fock quantization where both the dynamics and the SO(3)-symmetries of the field equations are unitarily implemented. The present work proves that this Fock representation is in fact unique inasmuch as, up to equivalence, there exists no other possible choice of SO(3)-invariant complex structure leading to a unitary implementation of the time evolution.Comment: 10 pages, minor changes, version accepted for publication in Classical and Quantum Gravit

Algumas espécies coprófilas de Psilocybe (Strophariaceae) do Estado de Pernambuco, Brasil

Coprophilous species Psilocybe argentina, P. pegleriana and P. cubensis are reported for the first time for Northeast Brazil. The last one is a hallucinogenic mushroom. Descriptions, discussions and drawings of the species are provided.As espécies coprófilas Psilocybe argentina, P. pegleriana e P. cubensis são referidas pela primeira vez para o Nordeste Brasileiro, sendo esta última uma espécie de cogumelo alucinógeno. Descrições, discussões e desenhos das espécies são fornecidos

Decoherence times of universal two-qubit gates in the presence of broad-band noise

The controlled generation of entangled states of two quantum bits is a fundamental step toward the implementation of a quantum information processor. In nano-devices this operation is counteracted by the solid-state environment, characterized by a broadband and non-monotonic power spectrum, often 1/f at low frequencies. For single-qubit gates, incoherent processes due to fluctuations acting on different time scales result in peculiar short- and long-time behavior. Markovian noise gives rise to exponential decay with relaxation and decoherence times, T1 and T2, simply related to the symmetry of the qubit-environment coupling Hamiltonian. Noise with the 1/f power spectrum at low frequencies is instead responsible for defocusing processes and algebraic short-time behavior. In this paper, we identify the relevant decoherence times of an entangling operation due to the different decoherence channels originating from solid-state noise. Entanglement is quantified by concurrence, which we evaluate in an analytic form employing a multi-stage approach. The 'optimal' operating conditions of reduced sensitivity to noise sources are identified. We apply this analysis to a superconducting \sqrt{i-SWAP} gate for experimental noise spectra.Comment: 35 pages, 11 figure

On the Schroedinger Representation for a Scalar Field on Curved Spacetime

It is generally known that linear (free) field theories are one of the few QFT that are exactly soluble. In the Schroedinger functional description of a scalar field on flat Minkowski spacetime and for flat embeddings, it is known that the usual Fock representation is described by a Gaussian measure. In this paper, arbitrary globally hyperbolic space-times and embeddings of the Cauchy surface are considered. The classical structures relevant for quantization are used for constructing the Schroedinger representation in the general case. It is shown that in this case, the measure is also Gaussian. Possible implications for the program of canonical quantization of midisuperspace models are pointed out.Comment: 11 pages, Revtex, no figure

Dinâmica e variabilidade espacial de plantas daninhas em sistemas de mobilização do solo em sorgo forrageiro.

O mapeamento e a caracterização da distribuição espacial de plantas daninhas por meio da agricultura de precisão, associada a levantamentos fitossociológicos, têm sido utilizados no controle localizado da infestação. O presente trabalho avaliou a incidência e a dinâmica de plantas daninhas, além da distribuição espacial em distintos sistemas de mobilização do solo, na cultura do sorgo forrageiro. O experimento foi conduzido em Petrolina-PE. Os tratamentos constaram de quatro sistemas de mobilização do solo: sem preparo primário, grade tandem mais arado de aivecas, grade off-set de discos de 0,61 m e grade tandem mais escarificador. A coleta de dados ocorreu na cultura do sorgo forrageiro aos 110 dias após emergência, em uma área retangular de 20 x 12 m (240 m²) com malha regular de 4 x 3 m, referenciadas em coordenadas x e y. A caracterização fitossociológica foi realizada pela avaliação da densidade, frequência, abundância, dominância e índice de valor de importância das espécies, e a variabilidade espacial, por meio da geoestatística com a construção de mapas de isolinhas. Cenchrus echinatus teve maior incidência e índice de valor de importância. O mapeamento de plantas daninhas tem relevância para a aplicação de métodos de controle, principalmente quando aliado ao levantamento fitossociológico

Kaposi's sarcoma with a non-Hodgkin's lymphoma. Its association in a male homosexual with human T-cell lymphotropic virus type III infection

Combined tumor syndromes, specifically reticuloendothelial malignancies and Kaposi’s sarcoma, have long been recognized. With the recognition of the acquired immunodeficiency syndrome (AIDS), several patients with concurrent non-Hodgkin’s lymphoma and Kaposi’s sarcoma have been reported at high risk for developing AIDS. The present Centers for Disease Control definition of AIDS excludes these patients on the assumption that one tumor is affecting the cellular immunity, allowing for the development of the second malignancy. In evaluating such a patient who had serologic evidence of human T-cell lymphotropic virus type III infection, the probable cause of AIDS, we have reviewed reports of patients with similar concurrent malignancies before and since the onset of the AIDS epidemic. We conclude that patients in high-risk groups for AIDS who develop similar combined tumor syndromes should be classified as having AIDS