Vacuum polarization induced by a cosmic string and a brane in AdS spacetime

In this paper we investigate the vacuum polarization effects associated to a charged quantum massive scalar field on a $(D+1)$-dimensional anti-de Sitter background induced by a magnetic-flux-carrying cosmic string in the braneworld model context. We consider the brane parallel to the anti-de Sitter boundary and the cosmic string orthogonal to them. Moreover, we assume that the field obeys the Robin boundary condition on the brane. Because the brane divides the space into two regions with different properties of the quantum vacuum, we calculate the vacuum expectation value (VEV) of the field squared and the energy-momentum tensor (EMT) in each region. To develop these analyses, we have constructed the positive frequency Wightman function for both regions. The latter is decomposed in a part associated with the anti-de Sitter bulk in the presence of a cosmic string only, and the other part induced by the brane. The vacuum polarization effects associated with the higher-dimensional anti-de Sitter bulk in the presence of cosmic string have been developed in the literature, and here we are mainly interested in the effects induced by the brane. We show that the VEVs of the field squared and the components of the EMT induced by the cosmic string are finite on the brane. Explicitly, we compare these observables with the corresponding ones induced by the brane only, and show that near the brane the contribution induced by the latter is larger than the one induced by the string; however, for points distant from the brane the situation is reversed. Moreover, some asymptotic expressions for the VEV of the field squared and EMT are provided for specific limiting cases of the physical parameters of the model. Also, an application of our results is given for a cosmic string in the $Z_2$-symmetric Randall-Sundrum braneworld model with a single brane.Comment: 23 pages, 4 figures; Version accepted for publication in EPJ

Induced fermionic current in AdS spacetime in the presence of a cosmic string and a compactified dimension

In this paper, we consider a massive charged fermionic quantum field and investigate the current densities induced by a magnetic flux running along the core of an idealized cosmic string in the background geometry of a 5-dimensional anti-de Sitter spacetime, assuming that an extra dimension is compactified. Along the compact dimension quasi-periodicity condition is imposed on the field with a general phase. Moreover, we admit the presence of a magnetic flux enclosed by the compactified axis. The latter gives rise to Ahanorov-Bohm-like effect on the vacuum expectation value of the currents. In this setup, only azimuthal and axial current densities take place. The former presents two contributions, with the first one due to the cosmic string in a 5-dimensional AdS spacetime without compact dimension, and the second one being induced by the compactification itself. The latter is an odd function of the magnetic flux along the cosmic string and an even function of the magnetic flux enclosed by the compactified axis with period equal to the quantum flux. As to the induced axial current, it is an even function of the magnetic flux along the string's core and an odd function of the magnetic flux enclosed by the compactification perimeter. For untwisted and twisted field along compact dimension, the axial current vanishes. The massless field case is presented as well as some asymptotic limits for the parameters of the model.Comment: 21 pages, 5 figures, PACS numbers: 03.70.+k 04.62.+v 04.20.Gz 11.27.+d, replaced typo in paragraph after eq. (3.18

Finite temperature charge and current densities around a cosmic string in AdS spacetime with compact dimension

For a massive scalar field with a general curvature coupling parameter, we investigate the finite temperature contributions to the Hadamard function and to the charge and current densities in the geometry of a magnetic flux carrying generalized cosmic string embedded in $(D+1)$-dimensional locally AdS spacetime with a compactified spatial dimension. For $D=4$, the geometry on the AdS boundary, in the context of the AdS/CFT duality, corresponds to a cosmic string as a linear defect, compactified along its axis. In contrast to the case of the Minkowski bulk, the upper bound on the chemical potential does not depend on the field mass and is completely determined by the length of compact dimension and by the enclosed magnetic flux. The only nonzero components correspond to the charge density, to the azimuthal current and to the current along the compact dimension. They are periodic functions of magnetic fluxes with the period equal to the flux quantum. The charge density is an odd function and the currents are even functions of the chemical potential. At high temperatures the influence of the gravitational field and topology on the charge density is subdominant and the leading term in the corresponding expansion coincides with that for the charge density in the Minkowski spacetime. The current densities are topology-induced quantities and their behavior at high temperatures is completely different with the linear dependence on the temperature. At small temperatures and for chemical potentials smaller than the critical value, the thermal expectation values are exponentially suppressed for both massive and massless fields.Comment: 30 pages, 7 figures; Version accepted for publication in Physical Review

Abordagens e metodologias para avaliação de germoplasma.

Abordagens e metodologias para avaliação de germoplasmas; Análise dos componentes principais; Abordagens e metodologias para avaliacao de germoplasma. Principais abordagens. Metodologias adotadas. Analise dos componentes principais. Desenvolvimento da metodologia. Analise das coordenatas principais. Desenvolvimento da metodologia. Análise de agrupamento. Medidas de similaridade. Distância de mahalanobis. Coeficiente simples de emparelhamento. Coeficiente de jaccard. Distância de rogers. Métodos de agrupamento. Métodos aglomerativos. Métodos do vizinho mais próximo. Método do vizinho mais distante. Método de otimização. Método de tocher. Metodologias para o estudo da diversidade genética. Índice de shannon e weaver. Análise da diversidade genética de nei. Distancia genetica de nei. Metodologia para o estudo da divergência genética. Passos da metologia. Relação entre divergência genética e heterose. Programas de computador para o emprego das técnicas de análise multivariada nos estudos dos gemoplasmas. Descrição dos programas. Programa: estandar.cm. programa: varcovar.cm. programa: corre.cm. Programa: conver.cm. Programa: cpp.cm.Programa: matriz.cm. Programa: Dme2.cm. Programa: dme4.cm. Programa: binário.cm. Descrição das rotinas. Exemplo de rotine para cálculo dos componentes principais. Exemplo de rotina para cálculo de distâncias. Exemplo de rotina para cálculo das coordenadas principais. Rotina para geração de matriz de similaridade, a partir de dados binários.bitstream/item/130109/1/Abordagens-e-metodologias-para-avaliacao.pd

Cosmic string and brane induced effects on the fermionic vacuum in AdS spacetime

We investigate the combined effects of a magnetic flux-carrying cosmic string and a brane on the fermionic condensate (FC) and on the vacuum expectation value (VEV) of the energy-momentum tensor for a massive charged fermionic field in background of 5-dimensional anti-de Sitter (AdS) spacetime. The brane is parallel to the AdS boundary and it divides the space into two regions with distinct properties of the fermionic vacuum. For two types of boundary conditions on the field operator and for the fields realizing two inequivalent representations of the Clifford algebra, the brane-induced contributions in VEVs are explicitly separated. The VEVs are even periodic functions of the magnetic flux, confined in the core, with the period of flux quantum. Near the horizon the FC and the vacuum energy-momentum tensor are dominated by the brane-free contribution, whereas the brane-induced part dominates in the region near the brane. Both the contributions vanish on the AdS boundary. At large distances from the cosmic string, the topological contributions in the VEVs, as functions of the proper distance, exhibit an inverse power-law decrease in the region between the brane and AdS horizon and an exponential decrease in the region between the brane and AdS boundary. We show that the FC and the vacuum energy density can be either positive or negative, depending on the distance from the brane. Applications are discussed in fermionic models invariant under the charge conjugation and parity transformation and also in $Z_{2}$% -symmetric braneworld models. By the limiting transition we derive the expressions of the FC and the vacuum energy-momentum tensor for a cosmic string on 5-dimensional Minkowski bulk in the presence of a boundary perpendicular to the string.Comment: 34 pages, 7 figures. Version accepted for publication in JHE