Paris West University Nanterre La Défense

About: Paris West University Nanterre La Défense is a education organization based out in Paris, France. It is known for research contribution in the topics: Computer science & Politics. The organization has 895 authors who have published 1430 publications receiving 21712 citations.

The mean field Schrödinger problem: ergodic behavior, entropy estimates and functional inequalities

Abstract: We study the mean field Schrodinger problem (MFSP), that is the problem of finding the most likely evolution of a cloud of interacting Brownian particles conditionally on the observation of their initial and final configuration Its rigorous formulation is in terms of an optimization problem with marginal constraints whose objective function is the large deviation rate function associated with a system of weakly dependent Brownian particles We undertake a fine study of the dynamics of its solutions, including quantitative energy dissipation estimates yielding the exponential convergence to equilibrium as the time between observations grows larger and larger, as well as a novel class of functional inequalities involving the mean field entropic cost (ie the optimal value in (MFSP)) Our strategy unveils an interesting connection between forward backward stochastic differential equations and the Riemannian calculus on the space of probability measures introduced by Otto, which is of independent interest

‘Il m'a sauté dessus’, ‘je lui ai couru après’: un cas de postposition en français

Abstract: Le debat sur le statut grammatical en francais (adverbes ou prepositions ?) de certains elements de la phrase a souvent porte sur le cas des ‘prepositions orphelines’. Dans ce cadre, on s'interesse au cas particulier des structures du type: ‘il m'a saute dessus’, ‘je lui ai couru apres’, ‘elle me tourne autour’, etc., ou un element prepositionnel (ou adverbial ?) se trouve postpose au pronom qu'il regit. Un examen systematique de ce type de constructions, tres frequentes en francais parle, met en evidence, sur la base d'inventaires et d'un corpus de francais parle et ecrit, leur statut particulier, du double point de vue syntaxique et semantique. Au-dela du strict point de vue syntaxique, l'examen debouche sur plusieurs observations: inventaire et nature des verbes et elements prepositionnels, domaines semantiques, statut lexical des unites ‘VII’ inventoriees.

Design and validation of a metasurface lens for converging vortex beams

Abstract: In this letter, a phase-gradient metasurface (MS) lens whose elements satisfy high transmittance and desired transmission phase is proposed to achieve collimation of vortex beams generated by an orbital angular momentum (OAM) radiating source. Two different phase profiles, hyperbolic and conical, are calculated and simulated. In addition, a prototype based on the conical phase profile is fabricated and experimentally tested, which verifies that the MS lens can realize effective collimation functionality. The proposed integrated lens-antenna system is able to provide new possibilities for OAM applications in radio wireless communication, imaging, and sensing.

Information Circulation in times of Ebola: Twitter and the Sexual Transmission of Ebola by Survivors

Abstract: INTRODUCTION The 2013-2015 outbreak of Ebola was by far the largest to date, affecting Guinea, Liberia, Sierra Leone, and secondarily, Nigeria, Senegal and the United States. Such an event raises questions about the circulation of health information across social networks. This article presents an analysis of tweets concerning a specific theme: the sexual transmission of the virus by survivors, at a time when there was a great uncertainty about the duration and even the possibility of such transmission. METHODS This article combines quantitative and qualitative analysis. From a sample of 50,000 tweets containing the words "Ebola" in French and English, posted between March 15 and November 8, 2014, we created a graphic representation of the number of tweets over time, and identified two peaks: the first between July 27 and August 16, 2014 (633 tweets) and the second between September 28 and November 8, 2014 (2,577 tweets). This sample was divided into two parts, and every accessible publication was analyzed and coded according to the authors' objectives, feelings expressed and/or publication type. RESULTS While the results confirm the significant role played by mainstream media in disseminating information, media did not create the debate around the sexual transmission of Ebola and Twitter does not fully reflect mainstream media contents. Social media rather work like a "filter": in the case of Ebola, Twitter preceded and amplified the debate with focusing more than the mainstream media on the sexual transmission, as expressed in jokes, questions and criticism. DISCUSSION Online debates can of course feed on journalistic or official information, but they also show great autonomy, tinged with emotions or criticisms. Although numerous studies have shown how this can lead to rumors and disinformation, our research suggests that this relative autonomy makes it possible for Twitter users to bring into the public sphere some types of information that have not been widely addressed. Our results encourage further research to understand how this "filter" works during health crises, with the potential to help public health authorities to adjust official communications accordingly. Without a doubt, the health authorities would be well advised to put in place a special watch on the comments circulating on social media (in addition to that used by the health monitoring agencies).

Could short selling make financial markets tumble

Abstract: It is suggested to consider long term trends of financial markets as a growth phenomenon. The question that is asked is what conditions are needed for a long term sustainable growth or contraction in a financial market? The paper discuss the role of traditional market players of long only mutual funds versus hedge funds which take both short and long positions. It will be argued that financial markets since their very origin and only till very recently, have been in a state of ``broken symmetry'' which favored long term growth instead of contraction. The reason for this ``broken symmetry'' into a long term ``bull phase'' is the historical almost complete dominance by long only players in financial markets. Dangers connected to short trading are illustrated by the appearence of long term bearish trends seen in analytical results and by simulation results of an agent based market model. Recent short trade data of the Nasdaq Composite index show an increase in the short activity prior to or at the same time as dips in the market, and reveal an steadily increase in the short trading activity, reaching levels never seen before.