Quasinormal modes of d-dimensional spherical black holes with a near extreme cosmological constant

We derive an expression for the quasinormal modes of scalar perturbations in near extreme d-dimensional Schwarzschild-de Sitter and Reissner-Nordstrom-de Sitter black holes. We show that, in the near extreme limit, the dynamics of the scalar field is characterized by a Poschl-Teller effective potential. The results are qualitatively independent of the spacetime dimension and field mass.Comment: 5 pages, REVTeX4, version to be published in Physical Review

Large Charge Four-Dimensional Non-Extremal N=2 Black Holes with R^2-Terms

We consider N=2 supergravity in four dimensions with small R^2 curvature corrections. We construct large charge non-extremal black hole solutions in all space, with either a supersymmetric or a non-supersymmetric extremal limit, and analyze their thermodynamic properties. This generalizes some of the extremal solutions presented in [arXiv:0902.0831]. The indexed entropy of the non-extremal extension of the supersymmetric black hole, has the form of the extremal entropy, with the charges replaced by a function of the charges, the moduli at infinity and the non-extremality parameter. This is the same behavior as in the case without R^2-terms.Comment: 13 pages. v2: stripped down to letter format, based on the background given in [arXiv:0902.0831]. v3: up to date with CQG versio

Gravitational quasinormal radiation of higher-dimensional black holes

We find the gravitational resonance (quasinormal) modes of the higher dimensional Schwarzschild and Reissner-Nordstrem black holes. The effect on the quasinormal behavior due to the presence of the $\lambda$ term is investigated. The QN spectrum is totally different for different signs of $\lambda$. In more than four dimensions there excited three types of gravitational modes: scalar, vector, and tensor. They produce three different quasinormal spectra, thus the isospectrality between scalar and vector perturbations, which takes place for D=4 Schwarzschild and Schwarzschild-de-Sitter black holes, is broken in higher dimensions. That is the scalar-type gravitational perturbations, connected with deformations of the black hole horizon, which damp most slowly and therefore dominate during late time of the black hole ringing.Comment: 13 pages, 2 figures, several references are adde

Black Holes, Space-Filling Chains and Random Walks

Many approaches to a semiclassical description of gravity lead to an integer black hole entropy. In four dimensions this implies that the Schwarzschild radius obeys a formula which describes the distance covered by a Brownian random walk. For the higher-dimensional Schwarzschild-Tangherlini black hole, its radius relates similarly to a fractional Brownian walk. We propose a possible microscopic explanation for these random walk structures based on microscopic chains which fill the interior of the black hole.Comment: 18 pages, 4 figures, 2 tables; v2 and v3: minor changes and refs. adde

Black Holes in Supergravity: the non-BPS Branch

We construct extremal, spherically symmetric black hole solutions to 4D supergravity with charge assignments that preclude BPS-saturation. In particular, we determine the ground state energy as a function of charges and moduli. We find that the mass of the non-BPS black hole remains that of a marginal bound state of four basic constituents throughout the entire moduli space and that there is always a non-zero gap above the BPS bound.Comment: 29 pages, one appendix, no figures; v2. few comments and references added and a missing sign included; v3. further references adde

Promoção do crescimento em mudas micropropagadas de bananeira por rizobactérias.

A micropropagação in vitro constitui uma ferramenta eficiente na obtenção de mudas sadias e homogêneas. Entretanto, a micropropagação também elimina a microbiota benéfica ao crescimento vegetativo. (Lazarovits e Nowak, 1997). A re-introdução de certos microrganismos tanto de forma individual como misturas de isolados, via tratamento de explantes, podem promover o crescimento das futuras plântulas e protegê-las contra doenças (Lazarovits e Nowak, 1997; Siddiqui e Shaukat, 2002). Rizobactérias ou PGPR (plant growth-promoting rhizobacteria) são bactérias saprófitas que vivem na rizosfera das plantas, e têm sido relacionadas com o incremento da produção agrícola como promotoras do crescimento de plantas e como agentes de biocontrole de doenças (Chen et al., 1996; Liu et al., 1995)pdf 121

Quasi-normal modes of Schwarzschild-de Sitter black holes

The low-laying frequencies of characteristic quasi-normal modes (QNM) of Schwarzschild-de Sitter (SdS) black holes have been calculated for fields of different spin using the 6th-order WKB approximation and the approximation by the P\"{o}shl-Teller potential. The well-known asymptotic formula for large $l$ is generalized here on a case of the Schwarzchild-de Sitter black hole. In the limit of the near extreme $\Lambda$ term the results given by both methods are in a very good agreement, and in this limit fields of different spin decay with the same rate.Comment: 9 pages, 1 ancillary Mathematica(R) noteboo

Generic bounds on dipolar gravitational radiation from inspiralling compact binaries

Various alternative theories of gravity predict dipolar gravitational radiation in addition to quadrupolar radiation. We show that gravitational wave (GW) observations of inspiralling compact binaries can put interesting constraints on the strengths of the dipole modes of GW polarizations. We put forward a physically motivated gravitational waveform for dipole modes, in the Fourier domain, in terms of two parameters: one which captures the relative amplitude of the dipole mode with respect to the quadrupole mode ($\alpha$) and the other a dipole term in the phase ($\beta$). We then use this two parameter representation to discuss typical bounds on their values using GW measurements. We obtain the expected bounds on the amplitude parameter $\alpha$ and the phase parameter $\beta$ for Advanced LIGO (AdvLIGO) and Einstein Telescope (ET) noise power spectral densities using Fisher information matrix. AdvLIGO and ET may at best bound $\alpha$ to an accuracy of $\sim10^{-2}$ and $\sim10^{-3}$ and $\beta$ to an accuracy of $\sim10^{-5}$ and $\sim10^{-6}$ respectively.Comment: Matches with the published versio

Superpotentials from flux compactifications of M-theory

In flux compactifications of M-theory a superpotential is generated whose explicit form depends on the structure group of the 7-dimensional internal manifold. In this note, we discuss superpotentials for the structure groups: G_2, SU(3) or SU(2). For the G_2 case all internal fluxes have to vanish. For SU(3) structures, the non-zero flux components entering the superpotential describe an effective 1-dimensional model and a Chern-Simons model if there are SU(2) structures.Comment: 10 page

Avaliação e identificação de Pseudomonas sp. e Bacillus sp. dois isolados de rizobactérias antagônicas a Radopholus similis.

As rizobactérias PGPR (plant growth-promoting rhizobacteria) são microrganismos que podem promover o desenvolvimento e crescimento de plantas e atuar no controle biológico de doenças. Bactérias dos gêneros Pseudomonas e Bacillus são amplamente conhecidas pela capacidade de atuarem no biocontrole de fitopatógenos, dentre esses, nematóides. Isso se deve, principalmente, pela produção direta de compostos tóxicos, alteração dos exsudatos radiculares ou da indução de resistência na planta hospedeira. Assim, o uso desses microrganismos como agentes de biocotnrole do Radopholus similis, causador de necroses radiculares, em bananeira, é um alternativa a ser estudada. Visando a identificação de isolados com potencial uso no controle de fitopatógenos, o emprego de técnicas moleculares torna-se uma ferramenta indispensável. Nesse sentido, a técnica de PCR (reação em cadeia da polimerase) é uma forma rápida e eficiente de caracterizar isolados promissores. Dessa forma, este estudo teve como objetivo avaliar o potencial de biocontrole in vitro das rizobactérias ao R. Similis, e identificar por meio de PCR, a prevalência dos gêneros Pseudomonas e Bacillus entre isolados pré-selecionados.PDF. 071