O Efeito Casimir para um Campo Fermiônico na Presença de um Campo Magnético Externo

Neste trabalho revisitamos a influência de um campo externo uniforme, particularmente de um campo magnético, sobre a energia de Casimir de um campo fermiônico [1, 2]. Recalculamos então o efeito Casimir nas condições citadas utilizando uma forma generalizada para as condições de contorno sobre o campo bem como o método da função zeta generalizada [3], o qual permite extrair um resultado final mais "limpo", i.e., um com menos termos divergentes espúrios

Hamiltonian formulation of nonAbelian noncommutative gauge theories

We implement the Hamiltonian treatment of a nonAbelian noncommutative gauge theory, considering with some detail the algebraic structure of the noncommutative symmetry group. The first class constraints and Hamiltonian are obtained and their algebra derived, as well as the form of the gauge invariance they impose on the first order action.Comment: enlarged version, 7 pages, RevTe

The Hamiltonian BRST quantization of a noncommutative nonabelian gauge theory and its Seiberg-Witten map

We consider the Hamiltonian BRST quantization of a noncommutative non abelian gauge theory. The Seiberg-Witten map of all phase-space variables, including multipliers, ghosts and their momenta, is given in first order in the noncommutative parameter $\theta$. We show that there exists a complete consistence between the gauge structures of the original and of the mapped theories, derived in a canonical way, once we appropriately choose the map solutions.Comment: 10 pages, Latex. Address adde

Approaches in biotechnological applications of natural polymers

Natural polymers, such as gums and mucilage, are biocompatible, cheap, easily available and non-toxic materials of native origin. These polymers are increasingly preferred over synthetic materials for industrial applications due to their intrinsic properties, as well as they are considered alternative sources of raw materials since they present characteristics of sustainability, biodegradability and biosafety. As definition, gums and mucilages are polysaccharides or complex carbohydrates consisting of one or more monosaccharides or their derivatives linked in bewildering variety of linkages and structures. Natural gums are considered polysaccharides naturally occurring in varieties of plant seeds and exudates, tree or shrub exudates, seaweed extracts, fungi, bacteria, and animal sources. Water-soluble gums, also known as hydrocolloids, are considered exudates and are pathological products; therefore, they do not form a part of cell wall. On the other hand, mucilages are part of cell and physiological products. It is important to highlight that gums represent the largest amounts of polymer materials derived from plants. Gums have enormously large and broad applications in both food and non-food industries, being commonly used as thickening, binding, emulsifying, suspending, stabilizing agents and matrices for drug release in pharmaceutical and cosmetic industries. In the food industry, their gelling properties and the ability to mold edible films and coatings are extensively studied. The use of gums depends on the intrinsic properties that they provide, often at costs below those of synthetic polymers. For upgrading the value of gums, they are being processed into various forms, including the most recent nanomaterials, for various biotechnological applications. Thus, the main natural polymers including galactomannans, cellulose, chitin, agar, carrageenan, alginate, cashew gum, pectin and starch, in addition to the current researches about them are reviewed in this article.. }To the Conselho Nacional de Desenvolvimento Cientfíico e Tecnológico (CNPq) for fellowships (LCBBC and MGCC) and the Coordenação de Aperfeiçoamento de Pessoal de Nvíel Superior (CAPES) (PBSA). This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2013 unit, the Project RECI/BBB-EBI/0179/2012 (FCOMP-01-0124-FEDER-027462) and COMPETE 2020 (POCI-01-0145-FEDER-006684) (JAT)

Departamento de Física da UEFS: sua natureza, diretrizes e perspectivas sob a ótica das considerações teórico-filosóficas consubstanciadas no seu projeto de criação

Neste trabalho, a partir do projeto de criação, analisamos a natureza, diretrizes e perspectivas do Departamento de Física da UEFS, sob a ótica das considerações teórico-filosóficas já estabelecidas. Ao final, realizamos uma avaliação sobre a evolução do DFIS nesses cinco anos iniciais, considerando as atividades desenvolvidas pelo departamento à luz das diretrizes e perspectivas delineadas

O Campo de Radiação Quantizado sob Vínculos Macroscópicos e a Pressão de Casimir no Calibre de Coulomb

O presente trabalho determina a pressão de Casimir seguindo as ideias da Eletrodinâmica Quântica Finita (Finite QED), i.e., construímos uma expressão para o tensor energia-momento (E-M) do campo de radiação quantizado de maneira a eliminar qualquer procedimento posterior de renormalização na obtenção de resultados finitos para os observáveis físicos, em particular, para a energia e o momento. O ponto de partida para este desenvolvimento é uma proposta de produto de operadores a ser utilizada na construção de observáveis, para os quais as medidas físicas sejam sempre resultados finitos. Com esta motivação, desenvolvemos o cálculo da pressão de Casimir no calibre de Coulomb considerando dois tipos de condições de fronteira: a de Dirichlet e a de Neumann

A Global Approach with Cutoff Exponential Function, Mathematically Well Defined at the Outset, for Calculating the Casimir Energy: The Example of Scalar Field

A global approach with cutoff exponential functions is used to obtain the Casimir energy of a massless scalar field in the presence of a spherical shell. The proposed method, mathematically well defined at the outset, makes use of two regulators, one of them to make the sum of the orders of Bessel functions finite and the other to regularize the integral involving the zeros of Bessel function. This procedure ensures a consistent mathematical handling in the calculations of the Casimir energy and allows a major comprehension on the regularization process when nontrivial symmetries are under consideration. In particular, we determine the Casimir energy of a scalar field, showing all kinds of divergences. We consider separately the contributions of the inner and outer regions of a spherical shell and show that the results obtained are in agreement with those known in the literature, and this gives a confirmation for the consistence of the proposed approach. The choice of the scalar field was due to its simplicity in terms of physical quantity spin

Duas Descrições Lagrangeanas para a Eletrodinâmica de London

A Eletrodinâmica de London é revisitada no contexto de duas descrições Lagrangianas. As equações de London descrevem o diamagnetismo extremo, característico dos supercondutores tipo I. Uma descrição Lagrangeana, em um primeiro caso, é estabelecida utilizando um multiplicador de Lagrange à Lagrangeana de Maxwell, enquanto na segunda descrição se utiliza a Lagrangeana de Proca. Mostramos que existe uma equivalência entre as duas Lagrangeanas e discutimos algumas das consequências dessa equivalência