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Cosmology with gamma-ray bursts: I. The Hubble diagram through the calibrated - correlation
No full textInternational audienceContext. Gamma-ray bursts (GRBs) are the most energetics explosions in the Universe. They are detectable up to very high redshifts. They may therefore be used to study the expansion rate of the Universe and to investigate the observational properties of dark energy, provided that empirical correlations between spectral and intensity properties are appropriately calibrated.Aims. We used the type Ia supernova (SN) luminosity distances to calibrate the correlation between the peak photon energy, Ep,i, and the isotropic equivalent radiated energy, Eiso in GRBs. With this correlation, we tested the reliability of applying these phenomena to measure cosmological parameters and to obtain indications on the basic properties and evolution of dark energy.Methods. Using 162 GRBs with measured redshifts and spectra as of the end of 2013, we applied a local regression technique to calibrate the Ep,i–Eiso correlation against the type Ia SN data to build a calibrated GRB Hubble diagram. We tested the possible redshift dependence of the correlation and its effect on the Hubble diagram. Finally, we used the GRB Hubble diagram to investigate the dark energy equation of state (EOS). To accomplish this, we focused on the so-called Chevalier-Polarski-Linder (CPL) parametrization of the dark energy EOS and implemented the Markov chain Monte Carlo (MCMC) method to efficiently sample the space of cosmological parameters.Results. Our analysis shows once more that the Ep,i–Eiso correlation has no significant redshift dependence. Therefore the high-redshift GRBs can be used as a cosmological tool to determine the basic cosmological parameters and to test different models of dark energy in the redshift region (z ≥ 3), which is unexplored by the SNIa and baryonic acoustic oscillations data. Our updated calibrated Hubble diagram of GRBs provides some marginal indication (at 1σ level) of an evolving dark energy EOS. A significant enlargement of the GRB sample and improvements in the accuracy of the standardization procedure is needed to confirm or reject, in combination with forthcoming measurements of other cosmological probes, this intriguing and potentially very relevant indication.Key words: cosmological parameters / dark energy / cosmology: theor
Contrasting evolutionary genome dynamics between domesticated and wild yeasts
No full textInternational audienceStructural rearrangements have long been recognized as an important source of genetic variation, with implications in phenotypic diversity and disease, yet their detailed evolutionary dynamics remain elusive. Here we use long-read sequencing to generate end-to-end genome assemblies for 12 strains representing major subpopulations of the partially domesticated yeast Saccharomyces cerevisiae and its wild relative Saccharomyces paradoxus. These population-level high-quality genomes with comprehensive annotation enable precise definition of chromosomal boundaries between cores and subtelomeres and a high-resolution view of evolutionary genome dynamics. In chromosomal cores, S. paradoxus shows faster accumulation of balanced rearrangements (inversions, reciprocal translocations and transpositions), whereas S. cerevisiae accumulates unbalanced rearrangements (novel insertions, deletions and duplications) more rapidly. In subtelomeres, both species show extensive interchromosomal reshuffling, with a higher tempo in S. cerevisiae. Such striking contrasts between wild and domesticated yeasts are likely to reflect the influence of human activities on structural genome evolution
Clustering multivariate functional data in group-specific functional subspaces
No full textWith the emergence of numerical sensors in many aspects of everyday life, there is an increasing need in analyzing multivariate functional data. This work fo-cuses on the clustering of those functional data, in order to ease their modeling and understanding. To this end, a novel clustering technique for multivariate functional data is presented. This method is based on a functional latent mixture model which fits the data in group-specific functional subspaces through a multivariate functional principal component analysis. A family of parsimonious models is obtained by constraining model parameters within and between groups. An EM-like algorithm is proposed for model inference and the choice of hyper-parameters is addressed through model selection. Numerical experiments on simulated datasets highlight the good performance of the proposed methodology compared to existing work. This algorithm is then applied for analyzing the pollution in U.S. cities for one year
Description-dependent Choices
No full textThe standard model of choice behavior relies on an implicit assumption that a decision maker is not affected by different descriptions of a given problem (description invariance). However, the behavioral economics and psychology literatures provide well-established evidence that descriptions do in fact influence decision makers. In this paper, we distinguish between descriptions of objects of choice and consequences of objects of choice in order to deduce a decision maker's preferences over the descriptions from observed choices over the consequences. We provide a choice theoretical foundation for maximizing preference relations subject to the class of framing effects where description invariance is violated. JEL Classification: D89, D90, D91
Simulation Toolbox for Studying Energy Consumption in Wired Networks
No full textInternational audienceNetworking infrastructures are considered to consume as much energy as terminal end-user equipment or data-centers. While energy consumption of wireless networks is a matter of concern since their beginning, it is not the case for wired networks as they do not rely on batteries, but on plugged equipment. Yet, facing growing consumption, energy-efficient techniques start to be implemented in wired networks. However, measuring the end-to-end energy consumption of wired networking infrastructures remains a real challenge for network operators and scientists. This article presents the ECOFEN (Energy Consumption mOdel For End-to-end Networks) framework which allows to support precise simulation of energy consumption of large-scale complex wired networks. The experimental validation shows that Ecofen provides accurate energy consumption values
Report on GRASTA 2017, 6th Workshop on GRAph Searching, Theory and Applications, Anogia, Crete, Greece, April 10 – April 13, 2017
No full textGraph searching involves a team of mobile agents (called searchers or pursuers or cops) that aims at capturing a set of escaping agents (called evaders or fugitives or robbers) that hide in a network modeled by a graph. There are many variants of graph searching studied in the literature, often referred to as a pursuit-evasion game or cops and robbers game. These variants are either application driven, i.e. motivated by problems in practice, or are inspired by foundational issues at the intersection of Computer Science, Discrete Mathematics, and Artificial Inteligence. As a result, many researchers from different areas of Mathematics, Computer Science and Operations Research are interested in problems related to graph searching.GRASTA 2017 is the main forum on graph searching and was held at the Anogia Academic Village, Anogia, Crete, Greece.It gathered 39 researchers from diverse areas of Theoretical Computer Science and Discrete Mathematics related to Graph Searching Games and their Applications both from the applied and the theoretical point of view. The scientific program of the workshop consisted of 18 regular talks, and an open problem session
Posters de médiation scientifique II : Tour de Magie et Binaire
No full textPosters de médiation scientifiquesCes posters font partie d'une série de posters que nous présentons lors de divers interventions de médiation (vulgarisation) scientifique (Fête de la Science, intervention dans des écoles, etc.). Nous essayons d'y présenter des bases théoriques (mathématiques) de l'algorithmique (Un algorithme est une suite finie et non ambiguë d'opérations ou d'instructions permettant de résoudre un problème ou d'obtenir un résultat) et structures de données (comment " coder " un nombre, une image, etc.).. Ici, nous présentons le codage binaire grâce à un tour de magie. Cela est généralisé à tout changement de bases. Une partie du contenu de ces posters est accessible dès l'école primaire (les parties concernant les puissances et les changements de bases peuvent être mises de côté sans problème). Les parties plus " mathématiques " peuvent être présentées à un niveau collège
Electoral basis of populist parties
No full textInternational audienceThe electoral success of populism has been one of the most significant political developments of recent decades, which has accelerated dramatically in the 2010s. While most of the research on populism has concentrated on conceptual issues, the analysis of populist discourse or explaining the rise of populist parties, the relevance of the ‘demand-side’ of populist politics is increasingly recognized in the literature on this subject (Pauwels 2014; Van Kessel 2013). This article engages in a review of that literature on the basis of electoral support for populist parties, and the motives of voters for supporting those parties. Working from the predominance of populism being defined as a ‘thin ideology’ (Mudde 2004), it addresses two dominant strands of research, which relate to the radical right-wing and left-wing manifestations of populism, to propose a review of current knowledge on the social and attitudinal basis of voting for radical populist parties. The last section identifies future research avenues in the field of populist electoral politics
Législatives 2017 : répercussions de la présidentielle et contre-performance du Front National
No full textNational audienceAu lendemain de l’échec présidentiel de Marine Le Pen, le Front national est entré très affaibli dans la campagne des législatives de juin 2017. A l’issue d’une campagne quasi-inexistante sur le terrain, sur fond de tensions internes, le FN recule fortement au soir du 11 juin, totalisant un peu plus de 2,9 millions de voix et 13,2% des suffrages. Une nouvelle fois, le FN s’est heurté en 2017 à la mécanique d’un scrutin législatif arrimé institutionnellement à la présidentielle. Présent dans 120 circonscriptions au second tour, il emporte au total 8 sièges au sein de la nouvelle Assemblée Nationale