Homotopy type of moduli spaces of G-Higgs bundles and reducibility of the nilpotent cone

Let G be a real reductive Lie group, and H-C the complexification of its maximal compact subgroup H subset of G. We consider classes of semistable G-Higgs bundles over a Riemann surface X of genus g >= 2 whose underlying H-C-principal bundle is unstable. This allows us to find obstructions to a deformation retract from the moduli space of G-Higgs bundles over X to the moduli space of H-C-bundles over X, in contrast with the situation when g = 1, and to show reducibility of the nilpotent cone of the moduli space of G-Higgs bundles, for G complex

Methodology for quality analysis of Regional Bathymetric Surfaces: From Brazilian South Coast to Hunter Channel

There are several projects looking for a better way to represent large areas of seabed mapping using Digital Terrain Models (DTMs). Nonetheless, the selection of a DTM becomes a challenge in which the result should reflect the model with the highest quality. Thus, this paper aims to promote the development of a methodology in order to apply a set of graphical and statistical tools capable of supporting quantitative and qualitative analysis by the comparison of one surface (called LEPLAC Sul) against other DTMs available (as ETOPO1 and GEBCO_2014) and against a bathymetric control data derived from hydrographic surveys. The outcomes show that LEPLAC Sul has achieved the highest index of quality, presenting itself as an efficient reference for further national scientific researches of middle scale, like those related to oceanographic and geomorphological modeling.Hay varios proyectos dedicados a investigar la mejor forma de mapear grandes regiones del fondo del mar y su representación a través de Modelos Digitales de Terreno (MDT). Sin embargo, al elegir el MDT se debe tener en cuenta el modelo de mayor calidad. Por lo tanto, este trabajo pretende promover el desarrollo de una metodología que utiliza un conjunto de herramientas gráficas y estadísticas las cuales auxilian en los análisis cuantitativos y cualitativos, por medio de la comparación de una superficie (LEPLAC Sul) con otros MDT disponibles (ETOPO1 y GEBCO_2014) y con un dato batimétrico de control recogido de los levantamientos hidrográficos. El resultado de las pruebas demuestra que la superficie batimétrica LEPLAC Sul alcanzó los mayores índices de calidad. Así, puede considerarse una referencia eficiente para los futuros análisis e investigaciones brasileñas de mediana escala, como el caso de los modelos oceanográficos o geomorfológicos submarinos.Il y a plusieurs projets qui visent la cartographie des fonds marins et sa représentation adéquate par les modèles de terrain numériques (MTN). Cependant, parmi les différentes options de surfaces marines disponibles, il est connu que le choix du MTN doit être basé sur la recherche du modèle de meilleure qualité. Ce travail a pour but de promouvoir le développement d’une méthodologie qui vise à l’application d’un ensemble d’outils graphiques et statistiques capables d’aider aux analyses quantitatives et qualitatives en comparant les surfaces d’intérêt (LEPLAC Sul) à d'autres dont l'accès est libre (ETOPO1 et GEBCO_2014) et aux données bathymétriques de contrôle dérivés des levés hydrographiques. Les résultats montrent que LEPLAC Sul a atteint l'indice de qualité le plus élevé et s'est présenté comme référence pour de futures analyses et études brésiliennes à moyenne échelle, telles que la modélisation océanographique et géomorphologiques

To each according to its degree: The meritocracy and topocracy of embedded markets

A system is said to be meritocratic if the compensation and power available to individuals is determined by their abilities and merits. A system is topocratic if the compensation and power available to an individual is determined primarily by her position in a network. Here we introduce a model that is perfectly meritocratic for fully connected networks but that becomes topocratic for sparse networks-like the ones in society. In the model, individuals produce and sell content, but also distribute the content produced by others when they belong to the shortest path connecting a buyer and a seller. The production and distribution of content defines two channels of compensation: a meritocratic channel, where individuals are compensated for the content they produce, and a topocratic channel, where individual compensation is based on the number of shortest paths that go through them in the network. We solve the model analytically and show that the distribution of payoffs is meritocratic only if the average degree of the nodes is larger than a root of the total number of nodes. We conclude that, in the light of this model, the sparsity and structure of networks represents a fundamental constraint to the meritocracy of societiesSupport from the MIT Media Lab Consortia, Fundación Caja Madrid (Spain), UAM-Santander (Spain) and CONICYT grants: Anillo en Complejidad Social SOC-1101 and Fondecyt 1110351 is gratefully acknowledge

Some apects of thermodinamic formalism of piecewise of smooth vector fields

In this paper we study some aspects of thermodynamic formalism, more specifically topological pressure and, as a consequence, topological entropy for piecewise smooth vector fields, using topological conjugation with shift maps and the Perron- Frobenius Operator. Some relationships between entropy and Hausdorff dimensions are also investigated

The Topology of Parabolic Character Varieties of Free Groups

Let G be a complex affine algebraic reductive group, and let K be a maximal compact subgroup of G. Fix elements h_1,...,h_m in K. For n greater than or equal to 0, let X (respectively, Y) be the space of equivalence classes of representations of the free group of m+n generators in G (respectively, K) such that for each i between 1 and m, the image of the i-th free generator is conjugate to h_i. These spaces are parabolic analogues of character varieties of free groups. We prove that Y is a strong deformation retraction of X. In particular, X and Y are homotopy equivalent. We also describe explicit examples relating X to relative character varieties.Comment: 16 pages, version 2 includes minor revisions and some modified proofs, accepted for publication in Geometriae Dedicat

Length-weight relationship of 11 fish species from a tributary of the Amazon river system in northern Brazil.

The length?weight relationships (LWRs) of 11 freshwater fish for eight families (Leporinus friderici, Pterophyllum scalare, Geophagus camopiensis, Curimata incompta, Astyanax bimaculatus, Tetragonopterus chalceus, Moenkhausia lepidura, Metynnis lippincottianus, Plagioscion squamosissimus, Hemiodus unimaculatusandColomesus asellus) captured in tributary of the Amazon River system (Brazil) were investigated. These results represent the first reference on the LWRs for all 11 species in the eastern Amazon

Patterns of the parasite communities in a fish assemblage of a river in the Brazilian Amazon region.

This paper characterizes the pattern of ectoparasite and endoparasite communities in an assemblage of 35 sympatric fish from different trophic levels in a tributary from the Amazon River system, northern Brazil. In detritivorous, carnivorous, omnivorous and piscivorous hosts, the species richness consisted of 82 ectoparasites and endoparasites, but protozoan ectoparasites such as Ichthyophthirius multifiliis, Piscinoodinium pillulare and Tripartiella sp. were dominant species predominated, such that they were present in 80% of the hosts. The taxon richness was in the following order: Monogenea > Nematoda > Digenea > Crustacea > Protozoa > Acanthocephala = Cestoda > Hirudinea. Among the hosts, the highest number of parasitic associations occurred in Satanoperca jurupari, Aequidens tetramerus, Hoplerythrinus unitaeniatus, Hoplosternum littorale, Cichlasoma amazonarum, Chaetobranchus flavescens, Squaliforma emarginata, Chaetobranchopsis orbicularis and Hoplias malabaricus. A weak positive correlation between ectoparasite abundance and length of the hosts was observed. Ectoparasite communities of detritivorous, carnivorous and omnivorous hosts were similar, but these differed from the communities of piscivorous hosts. Larval endoparasite species with low host specificity were the main determinants of the parasite infracommunity structure of the fish assemblage. Fish assemblage had few species of helminth that were specialist endoparasites, while many were parasites at the larval stage, infecting intermediate and paratenic hosts. Finally, carnivorous and omnivorous hosts harbored endoparasite communities that were more heterogeneous than those of detritivorous and piscivorous hosts. This result lends supports to the notion that the feeding habits of the host species are a significant factor in determining the endoparasites fauna

Distribution pattern of crustacean ectoparasites of freshwater fish from Brazil.

The purpose of this study was to use the informations relating to parasite crustaceans species that was published over the course of one century (1913 to 2013), in order to search for infestation and distribution patterns among these ectoparasites in Brazilian freshwater fish species. This search was carried out on 445 samples of 119 host fish of 27 families within the orders Characiformes, Perciformes, Clupeiformes, Mugiliformes, Osteoglossiformes, Symbranchiformes, Tetraodontiformes and Siluriformes from various regions of Brazil. We organized different host-parasite systems into matrices grouping species at different taxonomic and infestation levels and according to host parameters. Five families of parasites (Ergasilidae, Argulidae, Lernaeidae, Lernaeopodidae and Cymothoidae) distributed into 76 species of 27 genera were analyzed in the host samples, which presented dominance of Ergasilidae species, mainly from the genus Ergasilus. Some crustaceans are host and site-specific, especially in relation to fish in particular habitats and lifestyles (e.g. Perulernaea gamitanae, Anphira branchialisand Riggia paranensis), while other parasites frequently have no preference (e.g. Lernaea cyprinaceaand Braga patagonica). We found broadly similar distribution patterns for some crustacean species among the different localities, whereas other species showed well-defined geographical patterns, and these findings were discussed

Deciphering past and present atmospheric metal pollution of urban environments: The role of black crusts formed on historical constructions

Construction materials affected by black crusts (BCs) can be subjected to restoration, demolition, recycling or even to their management as waste products. Therefore, the determination of their chemical features should be considered a crucial step before undertaking any action. In this work, we present the development of an analytical methodology useful to be implemented as a routine screening tool to detect recent and past atmospheric emissions of heavy metals, nowadays superficially deposited or even encapsulated in BCs. For its development, BCs together with the underneath original substrate/construction material were sampled from the historical construction Punta Begona Galleries (Getxo, Basque Country, North of Spain). In order to detect quickly and in a cost-effective way the stratification of the metallic deposits in the BCs over time (surface or external/recent and internal/past), thin sections were analyzed by elemental spectroscopic imaging techniques (SEM-EDS and mu-ED-XRF). In the external part of the BCs, iron particles were mainly identified, whereas in the inner areas (past deposition events) of the most exposed BCs to the atmosphere, lead accumulations together with zinc and copper were identified. Additional Raman imaging studies allowed to perform the molecular speciation study of lead, identifying mainly laurionite (PbClOH) together with hydrocerussite (Pb-3(CO3)(2)(OH)(2)). The presence of the mentioned lead chloride hydroxide confirms the role of the marine aerosol (chloride input) in the formation of the metallic compounds. These experimental evidences were used to assist the chemical equilibrium models developed to explain the reactivity pathway, which lead to the formation of the identified compounds. Through ICP-MS and lead isotopic ratio analysis, more than 3000 mg kg(-1) of lead were quantified in the BCs, probably coming from the old emissions conducted by the old power station close to the construction,. That lead content can be high enough to consider those crusts as a source of metallic contamination and a possible risk to the environment and human health