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

Uniqueness of the Fock quantization of fields with unitary dynamics in nonstationary spacetimes

The Fock quantization of fields propagating in cosmological spacetimes is not uniquely determined because of several reasons. Apart from the ambiguity in the choice of the quantum representation of the canonical commutation relations, there also exists certain freedom in the choice of field: one can scale it arbitrarily absorbing background functions, which are spatially homogeneous but depend on time. Each nontrivial scaling turns out into a different dynamics and, in general, into an inequivalent quantum field theory. In this work we analyze this freedom at the quantum level for a scalar field in a nonstationary, homogeneous spacetime whose spatial sections have $S^3$ topology. A scaling of the configuration variable is introduced as part of a linear, time dependent canonical transformation in phase space. In this context, we prove in full detail a uniqueness result about the Fock quantization requiring that the dynamics be unitary and the spatial symmetries of the field equations have a natural unitary implementation. The main conclusion is that, with those requirements, only one particular canonical transformation is allowed, and thus only one choice of field-momentum pair (up to irrelevant constant scalings). This complements another previous uniqueness result for scalar fields with a time varying mass on $S^3$, which selects a specific equivalence class of Fock representations of the canonical commutation relations under the conditions of a unitary evolution and the invariance of the vacuum under the background symmetries. In total, the combination of these two different statements of uniqueness picks up a unique Fock quantization for the system. We also extend our proof of uniqueness to other compact topologies and spacetime dimensions.Comment: 12 page

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

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

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

Emerging and under-recognized Chagas cardiomyopathy in non-endemic countries

Due to recent population emigration movements, an epidemic of Chagas disease is currently menacing most developed countries. The authors report the case of a 53-year-old Brazilian woman living in Europe for the last 10 years who developed heart failure symptoms, having a previous symptomatic sinus node disease with a pacemaker implant at age of 40 years. The diagnosis was based on serology and myocardial biopsy and the patient was treated with nifurtimox. The authors emphasize the need of a high level of suspicion in patients with suggestive epidemiology and the need of populational screening of specific high risk groups. New treatment options are also discussed

Investigation of antifungal activity from Vismia guianensis (Aubl.) standardized extract.

ABSTRACT: In the Amazon, the use of medicinal plants by native populations is an important source of ethnopharmacological knowledge. Vismia guianensis (Aubl.) Choisy is widely used against diseases caused by fungi. Thus, the aim of this work was to evaluate the antifungal potential of the species Vismia guianensis (Aubl.) Choisy and the influence of extractive parameters on the antifungal activity. Dried extracts were prepared from leaves and tested for activity against the fungal species Candida albicans, Malassezia furfur, and Trichophyton rubrum. The most promising extract was obtained with polar solvents (methanol and ethanol), and no significant difference was measured between the activities exhibited by these extracts (MIC 410 μg/mL). RESUMO: Na Amazônia, o uso de plantas medicinais pelas populações nativas é uma importante fonte de conhecimento etnofarmacológico. Vismia guianensis (Aubl.) Choisy é amplamente utilizada contra doenças causadas por fungos. Assim, o objetivo deste trabalho foi avaliar o potencial antifúngico da espécie Vismia guianensis (Aubl.) Choisy e a influência de parâmetros extrativos na atividade antifúngica. Os extratos foram preparados a partir das folhas da espécie vegetal e testados quanto à atividade contra as espécies fúngicas Candida albicans, Malassezia furfur e Trichophyton rubrum. O extrato mais promissor foi obtido com solventes polares (metanol e etanol) e nenhuma diferença significativa foi encontrada entre as atividades exibidas por esses extratos (CIM 410 μg/mL).Título em Português: Investigação da atividade antifúngica de extrato padronizado de Vismia guianensis (Aubl.)

Depression and anxiety in systemic lupus erythematosus: The crosstalk between immunological, clinical, and psychosocial factors

Depression and anxiety cause severe loss of quality of life for patients with systemic lupus erythematosus. The causes and factors that contribute to these psychological manifestations in lupus are difficult to disentangle. This study compared clinical, psychological, and demographic factors between lupus patients, depressed patients, and rheumatoid arthritis patients to discover lupus-specific contributors to depression. Lupus-specific manifestations of depression were also investigated. Physiological, clinical, and psychosocial data were collected from 77 patients. ELISA was used to measure cytokine levels. Univariate and Multivariate analyses were used to compare the patient populations and identify correlations between key physical and psychological indicators. The prevalence of depression in the SLE cohort was 6 times greater than the healthy control subjects. Pain, IL-6, and Pittsburgh Sleep Quality index values were all significantly higher in SLE patients compared with the healthy control group (P < .001, P = .038, and P = .005, respectively). Anxiety levels were significantly higher in SLE patients compared to healthy and RA control patients (P = .020 and .011, respectively). Serum IL-10 concentrations, relationship assessment scale, and fatigue severity scale values were found to be correlated with depression among the SLE patients (P = .036, P = .007, and P = .001, respectively). Relationship assessment and fatigue severity scale scores were found to be the best indicators of depression for the SLE patients (P = .042 and .028, respectively). Fatigue Severity, relationship satisfaction, and IL-10 concentrations are indicators of depression in lupus patients. Despite also suffering from the pain and disability that accompanies chronic autoimmune disease, the rheumatoid arthritis patients had less anxiety and better relationship scores.The authors thank the Portugal Fulbright Commission for funding Dr. Pool

Letter to the Editor: Retrospective multicenter study reveals absence of MRSA-associated bovine mastitis in Brazil (1994 to 2016).

Made available in DSpace on 2020-01-14T18:14:15Z (GMT). No. of bitstreams: 1 Retrospectivemulticenterstudyrevealsabsence.pdf: 241426 bytes, checksum: deaa24c28e7420ff1b6f494ea79712df (MD5) Previous issue date: 2019bitstream/item/208728/1/Retrospective-multicenter-study-reveals-absence.pd

Influence of Biological Therapeutics, Cytokines, and Disease Activity on Depression in Rheumatoid Arthritis

Purpose: Rheumatoid arthritis (RA) is an often debilitating autoinflammatory disease. Patients with rheumatoid arthritis are often troubled by co-occurring depression or other psychological manifestations. RA patients have a variety of treatment options available, including biologicals that inhibit cytokines or immune cells. If these cytokines influence the psychological symptoms, then the use of cytokine inhibitors should modulate these symptoms.Methods: A cohort of 209 individuals was recruited. This group included 82 RA patients, 22 healthy subjects, 32 depressed control subjects, and 73 subjects with systemic lupus erythematosus. Of the RA patients, 51% were on a biological therapeutic. ELISA was used to measure cytokine levels. A variety of psychological assessments were used to evaluate depression, anxiety, sleep, fatigue, and relationship status. Clinical values were obtained from medical records.Results: IL-10 concentration was associated with depressive symptoms in the RA patients, healthy controls, and the lupus patients. In the patients with primary depression, depressive symptoms were associated with IL-6 and TNF-alpha. In RA patients, Tocilizumab use was associated with decreased depressive symptoms. 14 RA patients who were not using biologicals began using them by a one-month follow-up. In these patients, there was no significant change to any value except for fatigue.Conclusions: A variety of both biological and social factors influences depressive symptoms in RA. IL-10 and IL-6 are likely to be involved, since IL-10 concentration was associated with depression and Tocilizumab decreased depressive symptoms in the RA patients. The roles of these cytokines are different in RA and lupus, as high IL-10 in RA is associated with increased depressive symptoms, but high IL-10 in the lupus patients is associated with decreased depression. IL-6 was also associated with depressive symptoms in the patients with primary depression. These results strongly indicate that disease activity, including cytokine levels, has a strong impact on depressive symptoms.This study was supported by Portugal Fulbright Commission (Dr. Brian D. Poole)