Decay of charged scalar field around a black hole: quasinormal modes of R-N, R-N-AdS and dilaton black holes

It is well known that the charged scalar perturbations of the Reissner-Nordstrom metric will decay slower at very late times than the neutral ones, thereby dominating in the late time signal. We show that at the stage of quasinormal ringing, on the contrary, the neutral perturbations will decay slower for RN, RNAdS and dilaton black holes. The QN frequencies of the nearly extreme RN black hole have the same imaginary parts (damping times) for charged and neutral perturbations. An explanation of this fact is not clear but, possibly, is connected with the Choptuik scaling.Comment: 10 pages, LaTeX, 4 figures, considerable changes made and wrong interpretation of computations correcte

Quasi-Normal Modes of Schwarzschild Anti-De Sitter Black Holes: Electromagnetic and Gravitational Perturbations

We study the quasi-normal modes (QNM) of electromagnetic and gravitational perturbations of a Schwarzschild black hole in an asymptotically Anti-de Sitter (AdS) spacetime. Some of the electromagnetic modes do not oscillate, they only decay, since they have pure imaginary frequencies. The gravitational modes show peculiar features: the odd and even gravitational perturbations no longer have the same characteristic quasinormal frequencies. There is a special mode for odd perturbations whose behavior differs completely from the usual one in scalar and electromagnetic perturbation in an AdS spacetime, but has a similar behavior to the Schwarzschild black hole in an asymptotically flat spacetime: the imaginary part of the frequency goes as 1/r+, where r+ is the horizon radius. We also investigate the small black hole limit showing that the imaginary part of the frequency goes as r+^2. These results are important to the AdS/CFT conjecture since according to it the QNMs describe the approach to equilibrium in the conformal field theory.Comment: 2 figure

Probabilistic Non-Linear Registration with Spatially Adaptive Regularisation

This paper introduces a novel method for inferring spatially varying regularisa- tion in non-linear registration. This is achieved through full Bayesian inference on a probabilistic registration model, where the prior on the transformation parameters is parameterised as a weighted mixture of spatially localised com- ponents. Such an approach has the advantage of allowing the registration to be more flexibly driven by the data than a traditional globally defined regularisation penalty, such as bending energy. The proposed method adaptively determines the influence of the prior in a local region. The strength of the prior may be reduced in areas where the data better support deformations, or can enforce a stronger constraint in less informative areas. Consequently, the use of such a spatially adaptive prior may reduce unwanted impacts of regularisation on the inferred transformation. This is especially important for applications where the deformation field itself is of interest, such as tensor based morphometry. The proposed approach is demonstrated using synthetic images, and with application to tensor based morphometry analysis of subjects with Alzheimer’s disease and healthy controls. The results indicate that using the proposed spatially adap- tive prior leads to sparser deformations, which provide better localisation of regional volume change. Additionally, the proposed regularisation model leads to more data driven and localised maps of registration uncertainty. This paper also demonstrates for the first time the use of Bayesian model comparison for selecting different types of regularisation.<br/

The what, how, and why of trait‐based analyses in ecology

Functional diversity is increasingly used alongside taxonomic diversity to describe populations and communities in ecology. Indeed, functional diversity metrics allow researchers to summarise complex occupancy patterns in space and/or time across communities and/or populations in response to various stressors. In other words, investigating what, how, and why something is changing in an ecosystem by looking at changes of patterns under a certain process through a specific mechanism. However, as the diversity of functional diversity metrics and methods increases, it is often not directly clear which metric is more readily appropriate for which question. We studied the ability of different functional diversity metrics to recover patterns and signals from different processes linked to common assembly mechanisms in community ecology, such as environmental filtering, competitive exclusion, equalising fitness, and facilitation. Using both simulated data and an empirical dataset affected by more complex and nuanced mechanisms, we tested the effectiveness of different space occupancy metrics to recover the simulated or empirical changes. We show that different metrics perform differently when trying to capture signals from different approximations of common mechanisms relative to no mechanism at all (null). For example, competition was harder to disentangle from the null mechanisms compared to facilitation in our simulations. This emphasises the importance of not using a one-size-fits-all metric. Instead, researchers should carefully consider and test whether a particular metric will be effective in capturing a pattern of interest

Measurement of CP observables in B± → D(⁎)K± and B± → D(⁎)π± decays

Measurements of CP observables in B ± →D (⁎) K ± and B ± →D (⁎) π ± decays are presented, where D (⁎) indicates a neutral D or D ⁎ meson that is an admixture of D (⁎)0 and D¯ (⁎)0 states. Decays of the D ⁎ meson to the Dπ 0 and Dγ final states are partially reconstructed without inclusion of the neutral pion or photon, resulting in distinctive shapes in the B candidate invariant mass distribution. Decays of the D meson are fully reconstructed in the K ± π ∓ , K + K − and π + π − final states. The analysis uses a sample of charged B mesons produced in pp collisions collected by the LHCb experiment, corresponding to an integrated luminosity of 2.0, 1.0 and 2.0 fb −1 taken at centre-of-mass energies of s=7, 8 and 13 TeV, respectively. The study of B ± →D ⁎ K ± and B ± →D ⁎ π ± decays using a partial reconstruction method is the first of its kind, while the measurement of B ± →DK ± and B ± →Dπ ± decays is an update of previous LHCb measurements. The B ± →DK ± results are the most precise to date

Microbiological quality in the flour and starch cassava processing in traditional and model unit

O objetivo deste trabalho foi avaliar a qualidade microbiológica de farinha e fécula durante as diferentes etapas do processamento de mandioca, em unidades tradicionais e em uma unidade modelo. Foram determinados índices de coliformes totais e termotolerantes, Bacillus cereus, Salmonela spp., bactérias e fungos nas farinhas e féculas. Não foram observadas presenças de B. cereus e Salmonella spp. na farinha e fécula de mandioca produzidas nas unidades estudadas. A incidência microbiana diminui com o avanço da etapa do processamento para obtenção de farinha e foi menor na unidade modelo. Após o processo de torra, a carga microbiana estava de acordo com os valores preconizados pela legislação brasileira, concluindo-se que essa etapa pode ser considerada como crítica na obtenção de farinha. Na obtenção de fécula, a carga microbiana nas unidades tradicionais são maiores que na modelo, e o aumento do número de extrações promove o aumento da incidência de microrganismos, sendo recomendadas apenas quatro extrações. ______________________________________________________________________________________ ABSTRACT: The objective of this research was to evaluate microbiological contamination in the flour and starch during cassava processing in traditional and model units. The total and fecal coliforms indexes, Bacillus cereus, Salmonella, bacteria, yeast and fungi were determined. Bacillus cereus and Salmonella were not detected in any sample. The incidence of microorganisms decreased along the processing to obtain cassava flour, and is lower in model unit. After the roasting process, the microbial load was below the values established by the Brazilian legislation, and can be regarded as a critical step in obtaining cassava flour. Concerning starch production, the microbial load in the traditional units was higher than in the model units, and the increase of the extraction steps has promoted the growth of microorganisms. It’s recommended the used of only 4 extractions