Sur la dimension de certaines variétés de Kisin : le cas de la restriction des scalaires de GLd

Given a p-torsion representation of the absolute Galois group of a p-adic field, M. Kisin defines a moduli space, which was named Kisin variety afterwards by G. Pappas and M. Rapoport. These varieties were first introduced in order to prove several modularity results on Galois representations. They were also used for constructing certain Galois deformation rings and computing some of them. Besides, they were involved in a recent work aiming at defining an algebraic structure on the stack of torsion Galois representations. It turns out that these varieties are formally similar to affine Deligne-Lusztig varieties. In particular their definition extends to the framework of reductive groups. In this thesis, we study the dimension of some Kisin varieties corresponding to the scalar restriction of the general linear group GLd. Inspired by methods coming from Deligne-Lusztig theory and following works by E. Viehmann and X. Caruso, we define a stratification on the given Kisin variety. Then we bound from below and from above the dimension of the strata, and we address the problem of maximizing the dimension over all strata. This allows us to derive the announced bounds on the dimension. As for affine Deligne-Lusztig varieties, the sum of the positive roots appears in the bounds.A une représentation de p-torsion du groupe de Galois absolu d'un corps p-adique, M. Kisin associe un espace de modules, appelé par la suite variété de Kisin par G. Pappas et M. Rapoport. Ces variétés ont été introduites afin de démontrer plusieurs résultats de modularité sur les représentations galoisiennes. Elles se sont révélées utiles également pour construire certains anneaux de déformations voire les calculer. Plus récemment elles ont été utilisées pour munir le champ des représentations galoisiennes de torsion d'une structure algébrique. Par ailleurs ces variétés ressemblent formellement aux variétés de Deligne-Lusztig affines. En particulier leur définition s'étend dans le cadre de la théorie des groupes réductifs. Dans cette thèse, nous étudions la dimension de certaines variétés de Kisin dans le cas de la restriction des scalaires à la Weil du groupe linéaire général GLd. En nous basant sur des méthodes issues du cadre Deligne-Lusztig et en suivant les travaux de E. Viehmann et X. Caruso, nous définissons une stratification de la variété de Kisin. Nous encadrons ensuite la dimension des strates, puis étudions le problème de la maximisation de la dimension sur l'ensemble des strates. Cela permet de démontrer des encadrements pour la dimension des variétés de Kisin considérées. Comme dans le cas des variétés de Deligne-Lusztig affines, la somme des racines positives intervient dans l'encadrement de la dimension

Psychoacoustic investigation of auditory cues involved in human underwater sound localization

International audienceTheoretical arguments about underwater sound localization predict that auditory cuesused in air are impaired in water. However, long term acclimatization could emerge due toexposure to the environment. We have compared localization abilities of expert and novicedivers. The localization task was conducted for 8 azimuthal sound positions and 8 signals(0.4, 1, 2, 4, 6, 8, 10 kHz, white-noise). Results indicate that localization was better forexperts: they made more correct localizations and their directional response distribution wasless dispersed. These results demonstrate long term acclimatization in the processing oflocalization cues under water, particularly of interaural cues

Recognition of two new species of freshwater crabs from the Seychelles based on molecular evidence (Potamoidea: Potamonautidae).

The Afrotropical freshwater crab genus Seychellum is endemic to the granitic Seychelles in the Indian Ocean (Mahé, Silhouette, Praslin, La Digue and Frégate). Here we describe two new cryptic species of Seychellum that represent two evolutionarily separate lineages of a previously monotypic genus. This raises to three the number of species of freshwater crabs known from Seychelles. Each species is endemic to either one island (Silhouette) or to a pair of islands (Mahé and Frégate, or Praslin and La Digue). The three species can be clearly distinguished as separate lineages by DNA analysis, haplotyping and examination of gonopod characters. The recognition of S. silhouette, sp. nov. (endemic to Silhouette) and S. mahefregate, sp. nov. (endemic to Mahé and Frégate) reduces the range of the type species, S. alluaudi (A. Milne-Edwards & Bouvier, 1893) to La Digue and Praslin. Both dispersal and vicariance may have played a role in shaping the present distribution patterns of the Seychellois freshwater crabs

Dogs with hearing and/or visual impairment are as capable as any dogs to communicate and cooperate with humans.

International audienc

Investigation of auditory cues involved in human underwater sound localization

International audienceTheoretical arguments about underwater sound localization predict that auditory cues used in air areimpaired in water, resulting in a theoretical inability to locate sounds under water. An azimuth identification task wasconducted under water for 8 positions (0°, 45°, 90°, 135°, 180°, 225°, 270°, 315°) and 3 signals (400 Hz sine, 6 kHzsine, white-noise). Results demonstrate that localization was possible, at least for lateral positions, indicating thatinteraural cues are processed. The absence of spectral pinna cues may explain a large front/back confusion pattern

BINAURAL LOUDNESS OF MOVING SOURCES IN FREE FIELD: PERCEPTUAL MEASUREMENTS VERSUS AT-EAR LEVELS

International audienceMost investigations on the variations of loudness with the spatial position of a sound source have been made for static sounds. The purpose of this work was to study the loudness of a moving source. By analogy with studies on difference in loudness between sounds increasing or decreasing in intensity (without movement of the source), we studied the global loudness of a moving sound. The analogy with the sounds whose intensity varies is direct because the at-ear level depends on the position of the source, so a moving sound will create levels that vary over time at the entrance of the auditory canal. We measured the overall loudness of a moving source as a function of the starting and ending positions of the stimulus and of its direction of rotation. Overall, we did not find any overall loudness difference according to the direction of variation of the source. Moreover, the results obtained with a static sound seem to confirm, with absolute magnitude estimation, the amount of directional loudness sensitivity measured previously with an adaptive method. In free field, loudness depends on the position of the sound source (Sivonen and Ellermeier, 2006). In order to quantify the effect of the incidence angle on loudness, the directional loudness sensitivity (DLS) is measured. DSL is defined as the level difference required for equal loudness between a frontal reference sound (azimuth 0°, elevation 0°) and a test sound at a given position. A negative DLS means that the test sound has been perceived softer than the frontal sound and vice versa. In a previous study, we showed a decrease in DLS with an increase in azimuth of an amount of more than 10 dB on average (25 listeners, Meunier et al., 2016). Different studies have also examined the loudness of sounds that increase and sounds that decrease in level. For sounds that only differ in temporal envelop, it has been shown that the global loudness of a sound whose level increases is greater than the global loudness of a sound whose level decreases (Ponsot et al., 2015a, 2015b). This phenomenon has been called asymmetry in loudness. When a sound source is moving around a listener, the at-ear level of the sound varies. Moreover, if we refer to the studies on directional loudness, its loudness should also vary. The aim of the work presented here was to explore how global loudness of moving sounds is formed and the main point was to determine whether there is an asymmetry between sounds that move in opposite directions as their level and loudness also vary in opposite directions

Allozyme variation amongst populations of the freshwater crab, Potamonautes perlatus (Decapoda: Potamonautidae) in the Berg River system, Western Cape

The Cape river crab, Potamonautes perlatus, is widely distributed in streams and rivers of the Western Cape where it exhibits considerable morphological variation. Recent genetic work on populations in the Olifants River system has demonstrated the existence of a new cryptic species of river crab, while populations of P. perlatus in the nearby Berg River system remained uninvestigated. Six populations of P. perlatus  were collected from along the length of the Berg River system (125 km) and the genetic structure was investigated using allozyme electrophoresis. Results from 14 allozyme loci showed that the populations were genetically invariant across the river system. It is suggested that gene flow may be responsible for the poor genetic differentiation amongst populations in the Berg River system. The implication for future management of the system is briefly discussed