Einstein-Maxwell-scalar black holes: the hot, the cold and the bald

The phenomenon of spontaneous scalarisation of charged black holes (BHs) has recently motivated studies of various Einstein-Maxwell-scalar models. Within these models, different classes of BH solutions are possible, depending on the non-minimal coupling function $f(\phi)$, between the scalar field and the Maxwell invariant. Here we consider the class wherein both the (bald) electrovacuum Reissner-Nordstr\"om (RN) BH and new scalarised BHs co-exist, and the former are never unstable against scalar perturbations. In particular we examine the model, within this subclass, with a quartic coupling function: $f(\Phi) = 1+\alpha \Phi ^4$. The domain of existence of the scalarised BHs, for fixed $\alpha$, is composed of two branches. The first branch (cold scalarised BHs) is continuously connected to the extremal RN BH. The second branch (hot scalarised BHs) connects to the first one at the minimum value of the charge to mass ratio and it includes overcharged BHs. We then assess the perturbative stability of the scalarised solutions, focusing on spherical perturbations. On the one hand, cold scalarised BHs are shown to be unstable by explicitly computing growing modes. The instability is quenched at both endpoints of the first branch. On the other hand, hot scalarised BHs are shown to be stable by using the S-deformation method. Thus, in the spherical sector this model possesses two stable BH local ground states (RN and hot scalarised). We point out that the branch structure of BHs in this model parallels the one of BHs in five dimensional vacuum gravity, with [Myer-Perry BHs, fat rings, thin rings] playing the role of [RN, cold scalarised, hot scalarised] BHs.Comment: 12 pages, 6 figure

Random-energy model in random fields

The random-energy model is studied in the presence of random fields. The problem is solved exactly both in the microcanonical ensemble, without recourse to the replica method, and in the canonical ensemble using the replica formalism. The phase diagrams for bimodal and Gaussian random fields are investigated in detail. In contrast to the Gaussian case, the bimodal random field may lead to a tricritical point and a first-order transition. An interesting feature of the phase diagram is the possibility of a first-order transition from paramagnetic to mixed phase.Comment: 18 pages, 5 figures (included

Spatial dynamics of labor markets in Brazil

There was substantial spatial variation in labor market outcomes in Brazil over the 1990s. In 2000, about one-fifth of workers lived in apparently economically stagnant municipios where real wages declined but employment increased faster than the national population growth rate. More than one-third lived in apparently dynamic municipios, experiencing both real wage growth and faster-than-average employment growth. These areas absorbed more than half of net employment growth over the period. To elucidate this spatial variation, the authors estimate spatial labor supply and demand equations describing wage and employment changes of Brazilian municipios. They use Conley's spatial GMM technique to allow for instrumental variable estimation in the presence of spatially autocorrelated errors. The main findings include: (1) a very strong influence of initial workforce educational levels on subsequent wage growth (controlling for possibly confounding variables such as remoteness and climate); (2) evidence of positive spillover effects of own-municipio growth onto neighbors'wage and employment levels; (3) an exodus from farming areas; (4) relatively elastic response of wages to an increase in labor supply; and (5) evidence of a local multiplier effect from government transfers.Labor Markets,Economic Theory&Research,Economic Growth,Municipal Financial Management,Achieving Shared Growth

Alignment tests for low CMB multipoles

We investigate the large scale anomalies in the angular distribution of the cosmic microwave background radiation as measured by WMAP using several tests. These tests, based on the multipole vector expansion, measure correlations between the phases of the multipoles as expressed by the directions of the multipole vectors and their associated normal planes. We have computed the probability distribution functions for 46 such tests, for the multipoles l=2-5. We confirm earlier findings that point to a high level of alignment between l=2 (quadrupole) and l=3 (octopole), but with our tests we do not find significant planarity in the octopole. In addition, we have found other possible anomalies in the alignment between the octopole and the l=4 (hexadecupole) components, as well as in the planarity of l=4 and l=5. We introduce the notion of a total likelihood to estimate the relevance of the low-multipoles tests of non-gaussianity. We show that, as a result of these tests, the CMB maps which are most widely used for cosmological analysis lie within the ~ 10% of randomly generated maps with lowest likelihoods.Comment: References added, updated discussion on alignment with Ecliptic Plane. 12 Pages, 6 Figures. Results for additional maps, the normalized frequencies for the tests and a Mathematica Notebook that computes the tests can be found on http://fma.if.usp.br/~abramo/MVA.htm

Detection of a Moving Rigid Solid in a Perfect Fluid

In this paper, we consider a moving rigid solid immersed in a potential fluid. The fluid-solid system fills the whole two dimensional space and the fluid is assumed to be at rest at infinity. Our aim is to study the inverse problem, initially introduced in [3], that consists in recovering the position and the velocity of the solid assuming that the potential function is known at a given time. We show that this problem is in general ill-posed by providing counterexamples for which the same potential corresponds to different positions and velocities of a same solid. However, it is also possible to find solids having a specific shape, like ellipses for instance, for which the problem of detection admits a unique solution. Using complex analysis, we prove that the well-posedness of the inverse problem is equivalent to the solvability of an infinite set of nonlinear equations. This result allows us to show that when the solid enjoys some symmetry properties, it can be partially detected. Besides, for any solid, the velocity can always be recovered when both the potential function and the position are supposed to be known. Finally, we prove that by performing continuous measurements of the fluid potential over a time interval, we can always track the position of the solid.Comment: 19 pages, 14 figure

Towards a calcium-based rechargeable battery

The development of a rechargeable battery technology using light electropositive metal anodes would result in a breakthrough in energy density1. For multivalent charge carriers (Mn+), the number of ions that must react to achieve a certain electrochemical capacity is diminished by two (n = 2) or three (n = 3) when compared with Li+ (ref. 2). Whereas proof of concept has been achieved for magnesium3, 4, 5, the electrodeposition of calcium has so far been thought to be impossible6 and research has been restricted to non-rechargeable systems7, 8, 9, 10. Here we demonstrate the feasibility of calcium plating at moderate temperatures using conventional organic electrolytes, such as those used for the Li-ion technology. The reversibility of the process on cycling has been ascertained and thus the results presented here constitute the first step towards the development of a new rechargeable battery technology using calcium anodes.Authors are grateful to F. Fauth for his assistance during data collection at the ALBA Synchrotron. The authors thank the Toyota Battery Research division at Higashi Fuji (M6) for their financial support.Peer reviewe

Achados metálicos do Vouga e do Baixo Mondego (Centro de Portugal): contributos para a sua contextualização e interpretação

O objetivo deste texto é a apresentação do contexto físico de cinco achados ou conjuntos metálicos da bacia do Vouga e do Baixo-Mondego resultantes de trabalhos de prospeção efetuados no âmbito do projeto Enardas. Referimo-nos aos achados ou depósitos designados por Coles de Samuel e Vale Centeio, ambos no concelho de Soure; ao de Travassos, no concelho da Mealhada e ao de Baralhas, no concelho de Vale de Cambra. No primeiro foi possível identificar o local e o contexto cultural do conjunto metálico e perceber que este correspondia a um depósito fechado; no caso de Vale Centeio foi apenas identificado, no terreno, o local genérico do achado; no caso de Travassos foi relocalizado o achado e nos casos de Baralhas foram descritos com mais acuidade os contextos físicos dos locais de achado. Apesar das particularidades todos os achados apresentam alguns denominadores comuns em termos físicos: conectam-se, direta ou indiretamente, com pequenas bacias de receção ou nascentes, com sítios relativamente depressionários e com visibilidades restritas. Apesar desta última característica, todos estes locais se vinculam com vales agrícolas que visualizam. A conjugação da localização destes achados no espaço, com a sua morfologia e as suas características técnicas possibilitam-nos algumas interpretações de ordem cultural sobre as comunidades da Idade do Bronze que as depositaram.The aim of this paper is the presentation of the physical context of five metallic finds and hoards found in the Vouga and Lower Mondego basins and resulting from surveys made under the pro-ject Enardas. We refer to the findings and hoards called Coles de Samuel and Vale Centeio, both in the municipality of Soure; to Travassos, in the municipality of Aveiro and to Baralhas, in the municipality of Vale de Cambra. At first, it was possible to identify the location and the cultural context of the metallic hoard and realize that this corresponded to a closed deposit; in the case of Vale Centeio has been only identified in the field, the general location of the find; in hoard of Travassos has been relocated and the gold hoard of Baralhas the physical contexts of the find have been described more precisely. Although the specifics, all findings have some common denominators in physical terms: they are directly or indirectly connect with small watersheds or springs and in sites with restricted visibility. Despite this last feature, all these places are bound with agricultural valleys that visualize.The combination of the location of the finds in space, with its morphology and its technical characteris-tics, allow us some interpretations of cultural features of the Bronze Age communities that deposited them.Este trabalho foi efetuado no âmbito do projeto Espaços Naturais, Arquiteturas, Arte Rupestre e Deposições na Pré-história Recente da Fachada Ocidental do Centro e Norte Português: das Ações aos Significados - ENARDAS (PTDC/HIS-ARQ/112983/2009), financiado pelo Programa Operacional Temático Factores de Com-petitividade (COMPETE) e comparticipado pelo Fundo Comunitário Europeu FEDER.info:eu-repo/semantics/publishedVersio

Worldwide phylogeny of three-spined sticklebacks

Stickleback fishes in the family Gasterosteidae have become model organisms in ecology and evolutionary biology. However, even in the case of the most widely studied species in this family – the three-spined stickleback (Gasterosteus aculeatus) – the worldwide phylogenetic relationships and colonization history of the different populations and lineages remain poorly resolved. Using a large collection of samples covering most parts of the species distribution range, we subjected thousands of single nucleotide polymorphisms to coalescent analyses in order to reconstruct a robust worldwide phylogeny of extant G. aculeatus populations, as well as their ancestral geographic distributions using Statistical-Dispersal Vicariance and Bayesian Binary MCMC analyses. The results suggest that contemporary populations originated from the Pacific Ocean in the Late Pleistocene, and the Atlantic was colonized through the Arctic Ocean by a lineage that diverged from Pacific sticklebacks ca 44.6 Kya. This lineage contains two branches: one that is distributed in the Mediterranean area, from the Iberian Peninsula to the Black Sea (‘Southern European Clade’), and another that is comprised of populations from northern Europe and the east coast of North America (‘Trans-Atlantic Clade’). Hence, the results suggest that the North American East Coast was colonized by trans-Atlantic migration. Coalescence-based divergence time estimates suggest that divergence among major clades is much more recent than previously estimated.Peer reviewe

Virial identities in relativistic gravity: 1D effective actions and the role of boundary terms

Virial (aka scaling) identities are integral identities that are useful for a variety of purposes in nonlinear field theories, including establishing no-go theorems for solitonic and black hole solutions, as well as for checking the accuracy of numerical solutions. In this paper, we provide a pedagogical rationale for the derivation of such integral identities, starting from the standard variational treatment of particle mechanics. In the framework of one-dimensional (1D) effective actions, the treatment presented here yields a set of useful formulas for computing virial identities in any field theory. Then, we propose that a complete treatment of virial identities in relativistic gravity must take into account the appropriate boundary term. For General Relativity this is the Gibbons-Hawking-York boundary term. We test and confirm this proposal with concrete examples. Our analysis here is restricted to spherically symmetric configurations, which yield 1D effective actions (leaving higher-D effective actions and in particular the axially symmetric case to a companion paper). In this case, we show that there is a particular “gauge” choice, i.e. a choice of coordinates and parametrizing metric functions, that simplifies the computation of virial identities in General Relativity, making both the Einstein-Hilbert action and the Gibbons-Hawking-York boundary term noncontributing. Under this choice, the virial identity results exclusively from the matter action. For generic “gauge” choices, however, this is not the case.publishe