Pure motives with representable Chow groups

Let $k$ be an algebraically closed field. We show using Kahn's and Sujatha's theory of birational motives that a Chow motive over $k$ whose Chow groups are all representable belongs to the full and thick subcategory of motives generated by the twisted motives of curves. -- Motifs purs dont les groupes de Chow sont repr\'esentables. Soit $k$ un corps alg\'ebriquement clos. Nous prouvons, en nous servant de la th\'eorie des motifs birationnels d\'evelopp\'ee par Kahn et Sujatha, qu'un motif de Chow d\'efini sur $k$ dont les groupes de Chow sont tous repr\'esentables appartient \`a la sous-cat\'egorie pleine et \'epaisse des motifs engendr\'ee par les motifs de courbes tordus.Comment: 7 page

Testing Invariance in Risk Taking: A Comparison Between Anglophone and Francophone Groups

This article investigates the measurement invariance of 3 related constructs across 2 groups sampled from Anglophone and Francophone adult populations. Multiple-group confirmatory factor analyses explored the factor structures of the Domain-Specific Risk-Taking (DOSPERT) Scale (Weber, Blais, & Betz, 2002), the Risk-Taking scale of the Jackson Personality Inventory (Jackson, 1994), and the Sensation-Seeking Scale (Zuckerman, 1980; 1994) both within and between the 2 groups of 172 Anglophone and 187 Francophone participants. The psychometric properties of the original and translated instruments are discussed, as is the meaningfulness of using these scales in these populations. Le présent article se penche sur l’invariance des mesures de trois construits corrélés pour deux groupes échantillonnés issus de populations adultes anglophones et francophones. Des analyses factorielles confirmatoires de groupes multiples ont été conduites sur les structures factorielles de l’échelle Domain-Specific Risk-Taking (DOSPERT) (Weber, Blais, et Betz, 2002), de l’échelle de prise de risque de l’inventaire de personnalité (Personality Inventory) de Jackson (Jackson, 1994), et de l’échelle de recherche de sensations (Sensation-Seeking Scale) de Zuckerman (Zuckerman, 1980; 1994) aussi bien à l’intérieur de deux groupes de 172 participants anglophones et de 187 participants francophones qu’entre ces deux mêmes groupes. Nous discutons des propriétés psychométriques des instruments originaux et traduits, de même que de la pertinence d’utiliser ces échelles au sein des populations en question.measurement invariance, psychometric scale, risk taking, sensation seeking, échelle psychométrique, invariance des mesures, prise de risques, recherche de sensations

Homology and K-theory of the Bianchi groups

We reveal a correspondence between the homological torsion of the Bianchi groups and new geometric invariants, which are effectively computable thanks to their action on hyperbolic space. We use it to explicitly compute their integral group homology and equivariant $K$-homology. By the Baum/Connes conjecture, which holds for the Bianchi groups, we obtain the $K$-theory of their reduced $C^*$-algebras in terms of isomorphic images of the computed $K$-homology. We further find an application to Chen/Ruan orbifold cohomology. % {\it To cite this article: Alexander D. Rahm, C. R. Acad. Sci. Paris, Ser. I +++ (2011).

Some extremely amenable groups

A topological group $G$ is extremely amenable if every continuous action of $G$ on a compact space has a fixed point. Using the concentration of measure techniques developed by Gromov and Milman, we prove that the group of automorphisms of a Lebesgue space with a non-atomic measure is extremely amenable with the weak topology but not with the uniform one. Strengthening a de la Harpe's result, we show that a von Neumann algebra is approximately finite-dimensional if and only if its unitary group with the strong topology is the product of an extremely amenable group with a compact group.Comment: 7 pages, English with abridged French versio

Maximality of hyperspecial compact subgroups avoiding Bruhat-Tits theory

Let $k$ be a complete non-archimedean field (non trivially valued). Given a reductive $k$-group $G$, we prove that hyperspecial subgroups of $G(k)$ (i.e. those arising from reductive models of $G$) are maximal among bounded subgroups. The originality resides in the argument: it is inspired by the case of $\textrm{GL}_n$ and avoids all considerations on the Bruhat-Tits building of $G$.Comment: To appear at "Annales de l'Institut Fourier". This version avoids completely Berkovich geometr

La Responsabilité Sociétale de L'entreprise et Les Réactions des Parties Prenantes : le Cas de L'opérateur Téléphonique Mtn et des Utilisateurs de Téléphonie Mobile au Bénin

The purpose of this research is to understand the mechanisms by which the actions of corporate social responsibility can affect organizational commitment and organizational identification consumers. From an experiment performed with video support of social responsibility of the telephone operator MTN Benin, data were collected from a sample of judgment seven hundred and ten mobile phone users. The analysis shows that the consumer perception of the actions of social responsibility of the company affects their commitment and organizational identification. Socially responsible consumption appears as a moderating variable to put direct links days. However, the communication by the company on its "good deeds" does not seem to affect these relationships

Lorentzian Flat Lie Groups Admitting a Timelike Left-Invariant Killing Vector Field

We call a connected Lie group endowed with a left-invariant Lorentzian flat metric Lorentzian flat Lie group. In this Note, we determine all Lorentzian flat Lie groups admitting a timelike left-invariant Killing vector field. We show that these Lie groups are 2-solvable and unimodular and hence geodesically complete. Moreover, we show that a Lorentzian flat Lie group $(\mathrm{G},\mu)$ admits a timelike left-invariant Killing vector field if and only if $\mathrm{G}$ admits a left-invariant Riemannian metric which has the same Levi-Civita connection of $\mu$. Finally, we give an useful characterization of left-invariant pseudo-Riemannian flat metrics on Lie groups $\mathrm{G}$ satisfying the property: for any couple of left invariant vector fields $X$ and $Y$ their Lie bracket $[X,Y]$ is a linear combination of $X$ and $Y$