The Local Time Distribution of a Particle Diffusing on a Graph

We study the local time distribution of a Brownian particle diffusing along the links on a graph. In particular, we derive an analytic expression of its Laplace transform in terms of the Green's function on the graph. We show that the asymptotic behavior of this distribution has non-Gaussian tails characterized by a nontrivial large deviation function.Comment: 8 pages, two figures (included

Topological relaxation of entangled flux lattices: Single vs collective line dynamics

A symbolic language allowing to solve statistical problems for the systems with nonabelian braid-like topology in 2+1 dimensions is developed. The approach is based on the similarity between growing braid and "heap of colored pieces". As an application, the problem of a vortex glass transition in high-T_c superconductors is re-examined on microscopic levelComment: 4 pages (revtex), 4 figure

EMILIE BOURDU, MICHEL LALLEMENT, PIERRE VELTZ, THIERRY WEIL (DIR.), LE TRAVAIL EN MOUVEMENT

The digitization of productive processes leads to broad and deep reorganisations of professional activities, with new forms of engagement at work, more horizontal collaborations and changing societal regulations. This collective work analyzes these contemporary transformations by confronting theoretical conceptualizations with field experiments. The heuristic approach in the apprehension of the work is resolutely pluridisciplinary, combining the statistical observations with the results of experiments specific to certain workshops and territories and mobilizing a large panel of sources and experts of the social sciences to analyze the representations of the work, and its social or legal regulations. By investigating the transformations of work under the joint impact of the diffusion of digital technologies and the modification of the relationship of subordination in the context of an economy in the process of tertiarisation, the book is part of the pursuit of a questioning on the nature of the work, initiated by the colloquium of Cerisy in 2017. In the first place, the book describes the conditions of emergence of the responsibility of the agents in the classic organizations as well as its limits. Then, it examines the transformations of work induced by the digitization of activities in order to analyze the impact on the productive organization and the consequent consequences for salaried or self-employed workers. This is followed by the identification of new regulations emerging in response to these changes and the delineation of open negotiation spaces both nationally and internationally through this process. Finally, the experiments developing in the territories are described to pave the way for innovative forms of activity that stand out from the traditional professional methods.La numérisation des processus productifs entraîne de larges et profondes recompositions des activités professionnelles, avec des formes nouvelles d'engagement au travail, des collaborations plus horizontales et des régulations sociétales qui évoluent. Cet ouvrage collectif analyse ces transformations contemporaines en confrontant les conceptualisations théoriques aux expérimentations sur le terrain. L'approche heuristique dans l'appréhension du travail est résolument pluridisciplinaire, conjuguant les observations statistiques aux bilans d'expérimentations particulières à certains ateliers et territoires et mobilisant un large panel de sources et d'experts des sciences sociales pour analyser les représentations du travail, et ses régulations sociales ou juridiques. Par ses investigations sur les transformations du travail sous l'impact conjoint de la diffusion des technologies numériques et de la modification du lien de subordination dans le contexte d'une économie en voie de tertiarisation, l'ouvrage s'inscrit dans la poursuite d'un questionnement sur la nature du travail, initié par le colloque de Cerisy en 2017. En premier lieu, l'ouvrage décrit les conditions d'émergence de la responsabilité des agents dans les organisations classiques ainsi que ses limites. Puis, il examine les transformations du travail induites par la numérisation des activités pour analyser l'impact sur l'organisation productive et les conséquences qui en découlent pour les travailleurs salariés ou indépendants. S'en suit l'identification des nouvelles régulations émergeant en réponse à ces mutations et la délimitation des espaces de négociation ouverts tant au plan national qu'international par ce processus. Enfin, sont décrites les expérimentations se développant sur les territoires pour ouvrir la voie à des formes innovantes d'activité se démarquant des modalités professionnelles classiques

Jérôme Denis. Le Travail invisible des données. Eléments pour une sociologie des infrastructures

Cet ouvrage part d’une impuissance à décrypter que beaucoup d’entre nous éprouvent dans leur quotidien en manipulant des informations écrites et plus encore chiffrées sans avoir le loisir ni les moyens de soupeser l’impact des conditions de leur production et de leur circulation : ce que l’on tient pour « données » l’est-il vraiment ? Comment s’agencent les infrastructures matérielles et logicielles qui peuplent nos mondes numériques pour faire advenir des informations au statut de « données », puis en organiser la diffusion ?This work starts from an inability to decrypt that many of us experience in their daily lives by manipulating written information and more quantified without having the leisure or the means to weigh the impact of the conditions of their production and circulation: what is held for "data" is it really? How do the hardware and software infrastructures that populate our digital worlds fit together to bring information to the status of "data" and then organize its dissemination

Flow effects on multifragmentation in the canonical model

A prescription to incorporate the effects of nuclear flow on the process of multifragmentation of hot nuclei is proposed in an analytically solvable canonical model. Flow is simulated by the action of an effective negative external pressure. It favors sharpening the signatures of liquid-gas phase transition in finite nuclei with increased multiplicity and a lowered phase transition temperature.Comment: 13 pages, 5 Post Script figures (accepted for publication in PRC

Brownian Motion in wedges, last passage time and the second arc-sine law

We consider a planar Brownian motion starting from $O$ at time $t=0$ and stopped at $t=1$ and a set $F= \{OI_i ; i=1,2,..., n\}$ of $n$ semi-infinite straight lines emanating from $O$. Denoting by $g$ the last time when $F$ is reached by the Brownian motion, we compute the probability law of $g$. In particular, we show that, for a symmetric $F$ and even $n$ values, this law can be expressed as a sum of $\arcsin$ or $(\arcsin)^2$ functions. The original result of Levy is recovered as the special case $n=2$. A relation with the problem of reaction-diffusion of a set of three particles in one dimension is discussed

Exit and Occupation times for Brownian Motion on Graphs with General Drift and Diffusion Constant

We consider a particle diffusing along the links of a general graph possessing some absorbing vertices. The particle, with a spatially-dependent diffusion constant D(x) is subjected to a drift U(x) that is defined in every point of each link. We establish the boundary conditions to be used at the vertices and we derive general expressions for the average time spent on a part of the graph before absorption and, also, for the Laplace transform of the joint law of the occupation times. Exit times distributions and splitting probabilities are also studied and several examples are discussed.Comment: Accepted for publication in J. Phys.

Scattering theory on graphs

We consider the scattering theory for the Schr\"odinger operator -\Dc_x^2+V(x) on graphs made of one-dimensional wires connected to external leads. We derive two expressions for the scattering matrix on arbitrary graphs. One involves matrices that couple arcs (oriented bonds), the other involves matrices that couple vertices. We discuss a simple way to tune the coupling between the graph and the leads. The efficiency of the formalism is demonstrated on a few known examples.Comment: 21 pages, LaTeX, 10 eps figure

Quasi-gaussian fixed points and factorial cumulants in nuclear multifragmentation

We re-analyze the conditions for the phenomenon of intermittency (self-similar fluctuations) to occur in models of multifragmentation. Analyzing two different mechanisms, the bond-percolation and the ERW (Elattari, Richert and Wagner) statistical fragmentation models, we point out a common quasi-gaussian shape of the total multiplicity distribution in the critical range. The fixed-point property is also observed for the multiplicity of the second bin. Fluctuations are studied using scaled factorial cumulants instead of scaled factorial moments. The second-order cumulant displays the intermittency signal while higher order cumulants are equal to zero, revealing a large information redundancy in scaled factorial moments. A practical criterion is proposed to identify the gaussian feature of light-fragment production, distinguishing between a self-similarity mechanism (ERW) and the superposition of independent sources (percolation).Comment: 20 pages, uuencoded .tex file including 16 figure