Peak exclusion, stochasticity and convergence of perturbative bias expansions in 1+1 gravity

The Lagrangian peaks of a 1D cosmological random field representing dark matter are used as a proxy for a catalogue of biased tracers in order to investigate the small-scale exclusion in the two-halo term. The two-point correlation function of peaks of a given height is numerically estimated and analytical approximations that are valid inside the exclusion zone are derived. The resulting power spectrum of these tracers is investigated and shows clear deviations from Poisson noise at low frequencies. On large scales, the convergence of a perturbative bias expansion is discussed. Finally, we go beyond Gaussian statistics for the initial conditions and investigate the subsequent evolution of the two-point clustering of peaks through their Zel'dovich ballistic displacement, to clarify how exclusion effects mix up with scale-dependencies induced by nonlinear gravitational evolution. While the expected large-scale separation limit is recovered, significant deviations are found in the exclusion zone that tends in particular to be reduced at later times. Even though these findings apply to the clustering of one-dimensional tracers, they provide useful insights into halo exclusion and its impact on the two-halo term.Comment: 16 pages, 9 figures, accepted for publication in MNRA

A Low Level Component Model enabling Resource Specialization of HPC Applications

Scientific applications are still getting more complex, e.g. to improve their accuracy by taking into account more phenomena. Moreover, computing infrastructures are continuing their fast evolution. Therefore, software engineering is becoming a major issue to achieve easiness of development, portability, simple maintenance, while achieving high performance. Software component model is a promising approach, which enables to manipulate the software architecture of an application. However, existing models do not capture enough resource specificities. This paper proposes a low level component model (L2C) that supports directly native connectors such as MPI, shared memory and method invocation. L2C is intended to be used as a back end by a ''compiler'' (such as HLCM) to generate an application assembly specific to a given machine. This paper shows on a typical domain decomposition use case that \llc can achieve the same performance as native implementations, while gaining benefits such as enabling resource specialization capabilities.Les applications scientifiques continuent de devenir de plus en plus complexes, par exemple pour améliorer leur précision en intégrant davantage de phénomènes à simuler. Par ailleurs, les infrastructures de calcul continuent leur rapide évolution. Ainsi, l'ingénierie logicielle devient un défi très important afin de permettre une facilité de développement, la portabilité des codes, et une maintenance acceptable tout en permettant de hautes performances. Les modèles de composants logiciels offrent une approche prometteuse en permettant de manipuler l'architecture logicielle d'une application. Cependant, les modèles existant ne permettent pas de capturer suffisamment les spécificités des ressources de calcul. Cet article propose un modèle de composant logiciel ''bas niveau'' (L2C) qui permet l'intègration native de connecteurs tels que MPI, la mémoire partagée ou l'invocation de méthode. L2C est destiné à être utilisé en tant que langage de sortie d'un ''compilateur'' (tel que HLCM) générant un assemblage d'une application spécifique à une machine et à une exécution. Cet article montre sur un cas d'étude typique de décomposition de domaines que L2C permet d'atteindre les même performances que les applications natives, tout en offrant des possibilités d'optimisation par rapport aux capacités des ressources

Intrinsic alignment of simulated galaxies in the cosmic web: implications for weak lensing surveys

The intrinsic alignment of galaxy shapes (by means of their angular momentum) and their cross-correlation with the surrounding dark matter tidal field are investigated using the 160 000, z=1.2 synthetic galaxies extracted from the high-resolution cosmological hydrodynamical simulation Horizon-AGN. One- and two-point statistics of the spin of the stellar component are measured as a function of mass and colour. For the low-mass galaxies, this spin is locally aligned with the tidal field `filamentary' direction while, for the high-mass galaxies, it is perpendicular to both filaments and walls. The bluest galaxies of our synthetic catalog are more strongly correlated with the surrounding tidal field than the reddest galaxies, and this correlation extends up to 10 Mpc/h comoving distance. We also report a correlation of the projected ellipticities of blue, intermediate mass galaxies on a similar scale at a level of 10^(-4) which could be a concern for cosmic shear measurements. We do not report any measurable intrinsic alignments of the reddest galaxies of our sample. This work is a first step toward the use of very realistic catalog of synthetic galaxies to evaluate the contamination of weak lensing measurement by the intrinsic galactic alignments.Comment: 15 pages, accepted for publication in MNRA

Contribution à la conception à base de composants logiciels d'applications scientifiques parallèles

La conception d'applications scientifiques à base de couplage de code est une tâche complexe car elle demande de concilier une facilité de programmation et une obtention de haute performance. En outre, les ressources matérielles (supercalculateurs, grappes de calcul, grilles) permettant leur exécution forment un ensemble hétérogène en constante évolution. Les modèles à base de composants logiciels forment une piste prometteuse pour gérer ces deux sources de complexité car ils permettent d exprimer les interactions entre les différents constituants d une application tout en offrant des possibilités d'abstraction des ressources. Néanmoins, les modèles existants ne permettent pas d'exprimer de manière satisfaisante les applications constituées de motifs répliqués dynamiques et hiérarchiques. Ainsi, cette thèse vise à améliorer l'existant et en particulier la plate-forme générique de simulation numérique SALOME pour une classe d'applications très répandue : les applications à base de décomposition de domaine et la variante utilisant le raffinement de maillage adaptatif. Tout d'abord, nous avons proposé d étendre le modèle de composition spatial et temporel de SALOME en ajoutant la possibilité de définir dynamiquement la cardinalité des composants. Cela demande en particulier de gérer les communications de groupes ainsi induites. La proposition a été implémentée dans SALOME et validée via une application de décomposition de domaine à base de couplage de plusieurs instances de Code_Aster. Ensuite, nous avons étudié la pertinence d'utiliser un modèle de composant supportant des connecteurs natifs (MPI, mémoire partagée, appel de méthode) pour permettre une composition plus fine des interactions entre composants. Les résultats d'expériences montrent que des performances équivalentes aux versions natives sont obtenues tout en permettant de manipuler facilement l'architecture de l'application. Enfin, nous avons étudié les extensions nécessaires aux modèles à composants (abstraction,hiérarchie, dynamicité) pour la conception d applications de raffinement de maillage adaptatif. Les modèles de composants spatio-temporels les plus avancés permettent ainsi d'exprimer ce type d'application mais les performances sont limitées par leur mise en œuvre centralisée ainsi que par le manque de moyens efficaces pour modifier à la volée des assemblages de composants.Designing scientific applications based on code coupling is a complex task. It requires both an easy programming process and high-performance. In addition, execution resources (supercomputers, computer clusters, grids) are heterogeneous and constantly evolving. Software components models offer a promising perspective to manage this double complexity because they can express interactions between the different parts of an application while providing abstraction of resources. However, existing models cannot accurately express the applications made of dynamic and hierarchical patterns. The aim of this thesis is to improve the existing models, and in particular the generic platform for numerical simulation SALOME, for a class of widespread applications : applications based on domain decomposition, and its dynamic variant using adaptive mesh refinement. Firstly, we proposed to extend the spatial and temporal composition model provided by SALOME, by adding the ability to dynamically set component cardinality. This requires in particular to manage group communications induced. The proposal has been implemented into SALOME and validated via a domain decomposition application based on coupling several instances of Code_Aster.Then, we have studied the relevance of using a component model supporting native connectors (MPI, shared memory, method invocation), in order to allow finer composition interactions between components.The experiment results show that performances obtained are equivalent to those of the native versions, while allowing to easily manipulate the application architecture. Finally, we studied the necessary component models extensions (abstraction, hierarchy, dynamicity) for designing adaptative mesh refinement applications. The most advanced spatio-temporal component models can express this type of application but performances are limited by their centralized implementation and by the lack of efficient ways of modifying component assembling at execution time.LYON-ENS Sciences (693872304) / SudocSudocFranceF

Ocean-Atmosphere Application Scheduling within DIET

In this report, we tackle the problem of scheduling an Ocean-Atmosphere application in an heterogeneous environment. The application is used for long term climate forecast. In this context, we analyzed the execution of an experiment. An experiment is composed of several identical simulations composed of parallel tasks. On homogeneous platforms, we propose a heuristic and its optimizations, all based on the same idea: we divide the processors into disjoint sets, each group executing parallel tasks. On heterogeneous platforms the algorithm presented is applied on subsets of simulations. The computation of the subsets is done greedily and aims at minimizing the execution time by sending each subset on a cluster. We performed experiments on the french research grid \emph{Grid'5000} which exhibited some technical difficulties. We also present some modifications done to the heuristics to minimize the impact of these technical difficulties. Our simulations are then validated by experimentations

RadTalks: What Could Be Possible if the Law Really Stood for Black Lives?

A Series of Talks Delivered at the Law for Black Lives Convening, Organized by the Bertha Justice Institute at the Center for Constitutional Right

Coherent emotional perception from body expressions and the voice

Perceiving emotion from multiple modalities enhances the perceptual sensitivity of an individual. This allows more accurate judgments of others’ emotional states, which is crucial to appropriate social interactions. It is known that body expressions effectively convey emotional messages, although fewer studies have examined how this information is combined with the auditory cues. The present study used event-related potentials (ERP) to investigate the interaction between emotional body expressions and vocalizations. We also examined emotional congruency between auditory and visual information to determine how preceding visual context influences later auditory processing. Consistent with prior findings, a reduced N1 amplitude was observed in the audiovisual condition compared to an auditory-only condition. While this component was not sensitive to the modality congruency, the P2 was sensitive to the emotionally incompatible audiovisual pairs. Further, the direction of these congruency effects was different in terms of facilitation or suppression based on the preceding contexts. Overall, the results indicate a functionally dissociated mechanism underlying two stages of emotional processing whereby N1 is involved in cross-modal processing, whereas P2 is related to assessing a unifying perceptual content. These data also indicate that emotion integration can be affected by the specific emotion that is presented

Characterizing swells in the southern Pacific from seismic and infrasonic noise analyses

International audienceA temporary network of 10 broad-band seismic stations has been installed in French Polynesia for the Polynesian Lithosphere and Upper Mantle Experiment (PLUME). All the seismic stations were installed either on volcanic islands or on atolls of the various archipelagos of French Polynesia in a manner which complements the geographic coverage provided by the regional permanent stations. The primary aim of PLUME is to image the upper mantle structures related to plate motion and hotspot activity. However, because of its proximity to all sites, the ocean is responsible for a high level of noise in the seismic data and we show that these data can also be used to analyse ocean wave activity. The power spectral density (PSD) analyses of the seismic data recorded in French Polynesia show clear peaks in the 0.05– 0.10 Hz band (periods between 10 and 20 s), which corresponds to swell frequencies. Clear peaks in this frequency band are also observed in infrasonic data recorded on Tahiti. Ground motion analysis shows that the swell-related seismic noise (SRSN) is linearly polarized in the horizontal plane and its amplitude decreases rapidly with the distance from the shore. The microseismic and the infrasonic 'noise' amplitudes show very similar variations from station to station and both are strongly correlated with the swell amplitudes predicted by the National Oceanic and Atmospheric Administration (NOAA), wind-forced, 'WaveWatch' models. The swell direction can be estimated from SRSN polarization analysis but this has to be done with care since, for some cases, the ground motions are strongly controlled by the islands' anisometric shapes and by swell refraction processes. We find cases, however, such as Tahiti or roughly circular Tuamotu atolls, where the azimuth of the swell is in good agreement with the seismic estimates. We, therefore, demonstrate that the SRSN and the infrasonic signal observed in French Polynesia can be used in such cases as a proxy for swell amplitude and azimuth. From the continuous analysis of the data recorded in 2003 at the permanent seismic station PPTL in Tahiti, transfer functions have been obtained. This could provide a way to quantify the swell activity during the last two decades and, therefore, assist in the investigation of climate changes