Marcelo Guimarães - Academia.edu (original) (raw)

Papers by Marcelo Guimarães

In this work we apply different duality techniques, both the dual projection, based on the solder... more In this work we apply different duality techniques, both the dual projection, based on the soldering formalism and the master action, in order to obtain and study the dual description of the Carroll-Field-Jackiw model \cite{cfj}, a theory with a Chern-Simons-like explicitly Lorentz and CPT violating term, including the interaction with external charges. This Maxwell-Chern-Simons-like model may be rewritten in terms of the interacting modes of a massless scalar model and a topologically massive model \cite{mcs}, that are mapped, through duality, into interacting massless Maxwell and massive self-dual modes \cite{sd}. It is also shown that these dual modes might be represented into an unified rank-two self-dual model that represents the direct dual of the vector Maxwell-Chern-Simons-like model.

Revista brasileira de medicina veterinaria

ABSTRACT In this note, we consider the Landau gauge in the continuum formulation. Our purposes ar... more ABSTRACT In this note, we consider the Landau gauge in the continuum formulation. Our purposes are twofold. Firstly, we try to work out the consequences of the recently derived Cucchieri-Mendes bounds on the inverse Faddeev-Popov operator at the level of the path integral quantization. Secondly, we give an explicit renormalizable prescription to implement the so-called Landau B-gauges as introduced by Maas.

Journal of Physics a-Mathematical and Theoretical, 2007

We consider a massive relativistic particle in the background of a gravitational plane wave. The ... more We consider a massive relativistic particle in the background of a gravitational plane wave. The corresponding Green functions for both spinless and spin 1/2 cases, previously computed by A. Barducci and R. Giachetti [1], are reobtained here by alternative methods, as for example, the Fock-Schwinger proper-time method and the algebraic method. In analogy to the electromagnetic case, we show that for a gravitational plane wave background a semiclassical approach is also sufficient to provide the exact result, though the lagrangian involved is far from being a quadratic one.

Physical Review D, 2010

Restricting the functional integral to the Gribov region Ω leads to a deep modication of the beha... more Restricting the functional integral to the Gribov region Ω leads to a deep modication of the behavior of Euclidean Yang-Mills theories in the infrared region. For example, a gluon propagator of the Gribov type, k 2 k 4 +γ 4 , can be viewed as a propagating pair of unphysical modes, called here i-particles, with imaginary masses ±iγ 2 . From this viewpoint, gluons are unphysical and one can see them as being conned. We introduce a simple toy model describing how a suitable set of composite operators can be constructed out of i-particles whose correlation functions exhibit only real branch cuts, with associated positive spectral density. These composite operators can thus be called physical and are the toy analogy of glueballs in the Gribov-Zwanziger theory.

European Physical Journal C, 2011

The construction of BRST invariant local operators with the quantum numbers of the lightest glueb... more The construction of BRST invariant local operators with the quantum numbers of the lightest glueball states, J P C = 0 ++ , 2 ++ , 0 −+ , is worked out by making use of an Euclidean confining renormalizable gauge theory. The correlation functions of these operators are evaluated by employing a confining gluon propagator of the Gribov type and shown to display a spectral representation with positive spectral densities. An attempt to provide a first qualitative analysis of the ratios of the masses of the lightest glueballs is also discussed * capri@ufrrj.br † ajgomez@uerj.br ‡ msguimaraes@uerj.br § vitor@dft.if.uerj.br ¶ sorella@uerj.br Work supported by FAPERJ, Fundação de Amparoà Pesquisa do Estado do Rio de Janeiro, under the program Cientista do Nosso Estado, E-26/101.578/2010. * * dgtedesco@uerj.br 1 arXiv:1009.3062v2 [hep-th] 10 Dec 2010

Physical Review D, 2011

... with 045013-11 DAVID DUDAL AND MARCELO S. GUIMARAES [1] RJ Eden, PV Landshoff, DI Olive, and ... more ... with 045013-11 DAVID DUDAL AND MARCELO S. GUIMARAES [1] RJ Eden, PV Landshoff, DI Olive, and JC Polkinghorne, The Analytic S-Matrix (Cambridge University Press ... [31] PJ Silva and O. Oliveira, Proc. ... [39] MAL Capri, AJ Gomez, MS Guimaraes, VER Lemes, SP Sorella ...

Physical Review D, 2013

A dual Josephson junction corresponding to a (2 + 1)-dimensional non-superconducting layer sandwi... more A dual Josephson junction corresponding to a (2 + 1)-dimensional non-superconducting layer sandwiched between two (3 + 1)-dimensional dual superconducting regions constitutes a model of localization of a U (1) gauge field within the layer. Monopole tunneling currents flow from one dual superconducting region to another due to a phase difference between the wave functions of the monopole condensate below and above the non-superconducting layer when there is an electromagnetic field within the layer. These magnetic currents appear within the (2 + 1)-dimensional layer as a gas of magnetic instanton events and a weak electric charge confinement is expected to take place at very long distances within the layer. In the present work, we consider what happens when one introduces fermions in this physical scenario. Due to the dual Meissner effect featured in the dual superconducting bulk, it is argued that unconfined fermions would be localized within the (2 + 1)-dimensional layer, where their quantum fluctuations radiatively induce a Chern-Simons term, which is known to destroy the electric charge confinement and to promote the confinement of the magnetic instantons.

Annals of Physics, 2014

A study of the zero modes of the Faddeev-Popov operator in the maximal Abelian gauge is presented... more A study of the zero modes of the Faddeev-Popov operator in the maximal Abelian gauge is presented in the case of the gauge group SU (2) and for different Euclidean space-time dimensions. Explicit examples of classes of normalizable zero modes and corresponding gauge field configurations are constructed by taking into account two boundary conditions, namely: i) the finite Euclidean Yang-Mills action, ii) the finite Hilbert norm.

Veterinary Parasitology, 2014

The Neospora caninum microsatellite markers were applied to clinical samples. Genotyping technolo... more The Neospora caninum microsatellite markers were applied to clinical samples. Genotyping technology involving fluorescently labelled DNA fragment analysis was used in combination with DNA sequencing for markers with complex repetitive sequences. Nineteen DNA samples from 15 brains and four hearts of naturally infected non-aborted zebuine foetuses from abattoirs in Goiás, Brazil. N. caninum had been detected in these foetuses by nested-PCR of the internal transcribed spacer-1 rRNA region, and the samples were analysed using these microsatellites. Seven complete or nearly complete allele profiles were obtained from six foetuses. Three distinct profiles of N. caninum were identified in a unique microregion (Meia Ponte) of Goiás. Two alleles for the same marker were detected in a unique foetus that was probably infected with two different strains. A new allele for one of the microsatellites is described. The multilocus analysis performed here revealed a preliminary means of discriminating between individual strains according to their geographical origins. These are the first results that have been obtained regarding the molecular characterisation of strains of N. caninum from infected zebuine foetuses in South America and reveal for the first time that there are genotypic differences in the strains that are responsible for foetal transmission in zebuine foetuses.

Physical Review D, 2012

An equivalent formulation of the Gribov-Zwanziger theory accounting for the gauge fixing ambiguit... more An equivalent formulation of the Gribov-Zwanziger theory accounting for the gauge fixing ambiguity in the Landau gauge is presented. The resulting action is constrained by a Slavnov-Taylor identity stemming from a nilpotent exact BRST invariance which is spontaneously broken due to the presence of the Gribov horizon. This spontaneous symmetry breaking can be described in a purely algebraic way through the introduction of a pair of auxiliary fields which give rise to a set of linearly broken Ward identities. The Goldstone sector turns out to be decoupled. The underlying exact nilpotent BRST invariance allows to employ BRST cohomology tools within the Gribov horizon to identify renormalizable extensions of gauge invariant operators. Using a simple toy model and appropriate Dirac bracket quantization, we discuss the time-evolution invariance of the operator cohomology. We further comment on the unitarity issue in a confining theory, and stress that BRST cohomology alone is not sufficient to ensure unitarity, a fact, although well known, frequently ignored.

Pesquisa Veterinária Brasileira, 2011

RESUMO.-[Comparação de dois métodos para avaliação de glicocorticóides em lobos guarás.] A anális... more RESUMO.-[Comparação de dois métodos para avaliação de glicocorticóides em lobos guarás.] A análise de metabólitos de glicocorticóides fecais é uma ferramenta não-invasiva poderosa para o monitoramento da atividade adrenal em animais silvestres. Entretanto, diferenças no metabolismo e na excreção dessas substâncias tornam obrigatória a validação desse método para cada espécie e sexo investigado. Embora os lobos guarás (Chrysocyon brachyurus) sejam os maiores canídeos da América do Sul, seu comportamento e ϐisiologia são ainda pouco conhecidos e estes animais são ameaçados. Dois métodos para mensuração de metabólitos de glicocorticóides em lobos guarás ABSTRACT.-Vasconcellos A.S., Chelini M.O.M., Palme R., Guimarães M.A.B.V., Oliveira C.A. & Ades C. 2011. Comparison of two methods for glucocorticoid evaluation in maned wolves. Pesquisa Veterinária Brasileira 31(Supl.1):79-83. Analysis of faecal glucocorticoid metabolites provides a powerful noninvasive tool for monitoring adrenocortical activity in wild animals. However, differences regarding the metabolism and excretion of these substances make a validation for each species and sex investigated obligatory. Although maned wolves (Chrysocyon brachyurus) are the biggest canids in South America, their behaviour and physiology are poorly known and they are at risk in the wild. Two methods for measuring glucocorticoid metabolites in maned wolves were validated: a radio-and an enzyme immunoassay. An ACTH challenge was used to demonstrate that changes in adrenal function are reϐlected in faecal glucocorticoid metabolites. Our results suggest that both methods enable a reliable assessment of stress hormones in maned wolves avoiding short-term rises in glucocorticoid concentrations due to handling and restraint. These methods can be used as a valuable tool in studies of stress and conservation in this wild species. foram validados: um radio-e um enzima-imuno-ensaio. Um desaϐio de ACTH foi usado para demonstrar que alterações no funcionamento adrenal podem ser detectadas nas concentrações metabólitos de glicocorticóides fecais. Nossos resultados sugerem que ambos os métodos possibilitam uma avaliação conϐiável dos hormônios relacionados ao estresse em lobos guarás, evitando assim aumentos de curta duração nas concentrações glicocorticóides, devidos ao manejo e contenção. Esses métodos podem ser usados como uma ferramenta valiosa em estudos de estresse e conservação com essa espécie silvestre. TERMOS DE INDEXAÇÃO: ACTH, corticosterona, cortisol, imuno-ensaio, monitoramento não-invasivo, estresse.

The European Physical Journal C, 2013

The Astronomical …, 2007

We have carried out a major survey for visual binaries towards the Orion Nebula Cluster using HST... more We have carried out a major survey for visual binaries towards the Orion Nebula Cluster using HST images obtained with an Hα filter. Among 781 likely ONC members more than 60 ′′ from θ 1 Ori C, we find 78 multiple systems (75 binaries and 3 triples), of which 55 are new discoveries, in the range from 0. ′′ 1 to 1. ′′ 5. About 9 binaries are likely line-of-sight associations. We find a binary fraction of 8.8%±1.1% within the limited separation range from 67.5 to 675 AU. The field binary fraction in the same range is a factor 1.5 higher. Within the range 150 AU to 675 AU we find that T Tauri associations have a factor 2.2 more binaries than the ONC. The binary separation distribution function of the ONC shows unusual structure, with a sudden steep decrease in the number of binaries as the separation increases beyond 0. ′′ 5, corresponding to 225 AU. We have measured the ratio of binaries wider than 0. ′′ 5 to binaries closer than 0. ′′ 5 as a function of distance from the Trapezium, and find that this ratio is significantly depressed in the inner region of the ONC. The deficit of wide binaries in the central part of the cluster is likely due to dissolution or orbital change during their passage through the potential well of the inner cluster region. Many of the companions are likely to be brown dwarfs.

… and Applied Acarology, 2010

To ascertain whether brown dog tick Rhipicephalus sp. infests resistant (beagle) and susceptible ... more To ascertain whether brown dog tick Rhipicephalus sp. infests resistant (beagle) and susceptible (English cocker spaniel) dogs differently, five animals of each breed were maintained in a kennel whose walls were infested with 7,000 larvae, 320 nymphs, 80 males and 80 ...

Revista de Patologia …, 2010

O crescente número de animais de companhia em áreas urbanas, principalmente cães (Canis familiari... more O crescente número de animais de companhia em áreas urbanas, principalmente cães (Canis familiaris) e gatos (Felis catus), tem como consequência o estreitamento do contato desses animais com o homem, aumentando sua exposição às zoonoses. Com o objetivo de verificar a ocorrência de helmintos gastrintestinais em cães errantes em Goiânia e suas possíveis implicações em saúde pública, foram analisadas 201 amostras fecais de cães de rua recolhidos pelo Centro de Controle de Zoonoses. As amostras foram colhidas no período de fevereiro a maio de 2007 e examinadas segundo as técnicas convencionais para pequenos animais. Foram encontrados ovos das seguintes espécies de helmintos: Ancylostoma sp. (45,3%), Toxocara canis (8%), Trichuris vulpis (1%) e Dipylidium caninum (1%). A infecção isolada causada por Ancylostoma sp. foi observada em maior porcentagem, demonstrando o risco potencial da transmissão de zoonoses causadas por helmintos gastrintestinais de cães. Tal fato reforça a necessidade de medidas efetivas de saúde pública para que seja reduzida a ocorrência desses parasitos e sua possível transmissão ao homem. DESCRITORES: Helmintos. Ancylostoma. Cães errantes. Zoonose. Saúde pública.

Annals of Physics, 2013

An all orders algebraic proof of the multiplicative renormalizability of the novel formulation of... more An all orders algebraic proof of the multiplicative renormalizability of the novel formulation of the Gribov-Zwanziger action proposed in [1], and allowing for an exact but spontaneously broken BRST symmetry, is provided. *