Conformal Klein-Gordon equations and quasinormal modes

Using conformal coordinates associated with conformal relativity -- associated with de Sitter spacetime homeomorphic projection into Minkowski spacetime -- we obtain a conformal Klein-Gordon partial differential equation, which is intimately related to the production of quasi-normal modes (QNMs) oscillations, in the context of electromagnetic and/or gravitational perturbations around, e.g., black holes. While QNMs arise as the solution of a wave-like equation with a Poschl-Teller potential, here we deduce and analytically solve a conformal radial d'Alembert-like equation, from which we derive QNMs formal solutions, in a proposed alternative to more completely describe QNMs. As a by-product we show that this radial equation can be identified with a Schrodinger-like equation in which the potential is exactly the second Poschl-Teller potential, and it can shed some new light on the investigations concerning QNMs.Comment: 13 pages, 10 figure

Intra-group diffuse light in compact groups of galaxies. HCG 79, HCG 88 and HCG 95

Deep $B$ and $R$ images of three Hickson Compact Groups, HCG 79, HCG 88 and HCG 95, were analyzed using a new wavelet technic to measure possible intra-group diffuse light present in these systems. The method used, OV\_WAV, is a wavelet technic particularly suitable to detect low-surface brightness extended structures, down to a $S/N = 0.1$ per pixel, which corresponds to a 5-$\sigma$-detection level in wavelet space. The three groups studied are in different evolutionary stages, as can be judged by their very different fractions of the total light contained in their intra-group halos: $46\pm11$% for HCG 79 and $11\pm26$% for HCG 95, in the $B$ band, and HCG 88 had no component detected down to a limiting surface brightness of $29.1 B mag arcsec^{-2}$. For HCG 95 the intra-group light is red, similar to the mean colors of the group galaxies themselves, suggesting that it is formed by an old population with no significant on-going star formation. For HCG 79, however, the intra-group material has significantly bluer color than the mean color of the group galaxies, suggesting that the diffuse light may, at least in part, come from stripping of dwarf galaxies which dissolved into the group potential well.Comment: Two suggested references added to the introductio

Intra-group Light in Hickson Compact Groups

We have analyzed the intra-group light component of 3 Hickson Compact Groups (HCG 79, HCG 88 and HCG 95) with detections in two of them: HCG 79, with $46\pm11$ of the total $B$ band luminosity and HCG 95 with $11\pm26$. HCG 88 had no component detected. This component is presumably due to tidally stripped stellar material trapped in the group potential and represents an efficient tool to determine the stage of dynamical evolution and to map its gravitational potential. To detect this low surface brightness structure we have applied the wavelet technique OV\_WAV, which separates the different components of the image according to their spatial characteristic sizes.Comment: Small update on the associated institutions lis

The financial performance evaluation of the oil and gas industry through cash flow ratios in the period from 2014 to 2019

Este estudo foca especificamente nos indicadores de desempenho financeiro obtidos através da Demonstração de Fluxo de Caixa (DFC) sugeridos por Braga e Marques (2001), com ênfase no fluxo de caixa das atividades operacionais. A seleção das empresas foi feita com base no valor de mercado para reforçar a relevância da pesquisa. Foram analisadas as 10 principais empresas de Petróleo e Gás, de capital aberto, com ações negociadas na SEC que publicam anualmente suas demonstrações financeiras no formato 20-F ou 10-K, no período de 2014 a 2019. O estudo pretende dar continuidade à pesquisa feita anteriormente por Abrahão, Carvalho e Marques (2015) para o período de 2010 a 2013. Os dados utilizados nesta pesquisa foram obtidos por meio do banco de dados do site Evaluate Energy. A análise dos resultados dos índices calculados mostra que a amostra seguiu um padrão semelhante de crescimento e redução ao longo dos seis anos observado em quase todas as categorias analisadas, para a maioria das empresas. O único indicador destoante foi o de qualidade do resultado, que não demonstrou um padrão consistente. Percebeu-se também que 2014 e 2018 foram os anos em que o maior lucro líquido foi apurado para a maioria das empresas analisadas, o que gerou um alto valor de dividendos pagos aos acionistas e o maior fluxo de caixa dos resultados operacionais no período analisado

ANAEROBIC TREATMENT OF SULFATE LADEN IWASTEWATER WITH SIMULTANEOUS REMOVAL OF HYDROGEN SULFIDE USING BIOCHAR

Ph.D

Domain size heterogeneity in the Ising model: geometrical and thermal transitions

A measure of cluster size heterogeneity ($H$), introduced by Lee et al [Phys. Rev. E {\bf 84}, 020101 (2011)] in the context of explosive percolation, was recently applied to random percolation and to domains of parallel spins in the Ising and Potts models. It is defined as the average number of different domain sizes in a given configuration and a new exponent was introduced to explain its scaling with the size of the system. In thermal spin models, however, physical clusters take into account the temperature-dependent correlation between neighboring spins and encode the critical properties of the phase transition. We here extend the measure of $H$ to these clusters and, moreover, present new results for the geometric domains for both $d=2$ and 3. We show that the heterogeneity associated with geometric domains has a previously unnoticed double peak, thus being able to detect both the thermal and percolative transition. An alternative interpretation for the scaling of $H$ that does not introduce a new exponent is also proposed.Comment: 7 pages, 4 figure