Generalized Langevin equations for a driven tracer in dense soft colloids: construction and applications

We describe a tracer in a bath of soft Brownian colloids by a particle coupled to the density field of the other bath particles. From the Dean equation, we derive an exact equation for the evolution of the whole system, and show that the density field evolution can be linearized in the limit of a dense bath. This linearized Dean equation with a tracer taken apart is validated by the reproduction of previous results on the mean-field liquid structure and transport properties. Then, the tracer is submitted to an external force and we compute the density profile around it, its mobility and its diffusion coefficient. Our results exhibit effects such as bias enhanced diffusion that are very similar to those observed in the opposite limit of a hard core lattice gas, indicating the robustness of these effects. Our predictions are successfully tested against molecular dynamics simulations.Comment: 21 pages, 7 figure

Sensitivity of synthetic aperture laser optical feedback imaging

In this paper we compare the sensitivity of two imaging configurations both based on Laser Optical Feedback Imaging (LOFI). The first one is direct imaging, which uses conventional optical focalisation on target and the second one is made by Synthetic Aperture (SA) Laser, which uses numerical focalisation. We show that SA configuration allows to obtain good resolutions with high working distance and that the drawback of SA imagery is that it has a worse photometric balance in comparison to conventional microscope. This drawback is partially compensated by the important sensitivity of LOFI. Another interest of SA relies on the capacity of getting a 3D information in a single x-y scan

Scaling of the glassy dynamics of soft repulsive particles: a mode-coupling approach

We combine the hyper-netted chain approximation of liquid state theory with the mode-coupling theory of the glass transition to analyze the structure and dynamics of soft spheres interacting via harmonic repulsion. We determine the locus of the fluid-glass dynamic transition in a temperature -- volume fraction phase diagram. The zero-temperature (hard sphere) glass transition influences the dynamics at finite temperatures in its vicinity. This directly implies a form of dynamic scaling for both the average relaxation time and dynamic susceptibilities quantifying dynamic heterogeneity. We discuss several qualitative disagreements between theory and existing simulations at equilibrium. Our theoretical results are, however, very similar to numerical results for the driven athermal dynamics of repulsive spheres, suggesting that `mean-field' mode-coupling approaches might be good starting points to describe these nonequilibrium dynamics.Comment: 11 pages, 8 figure

Multimodal counter-argumentation in the workplace : the contribution of gesture and gaze to the expression of disagreement

This paper examines argumentative talk-in-interaction in the workplace. It focuses on counter-argumentative references, which consist of the various resources that the opponent uses to refer to the origin/source of his/her opposition, namely the confronted position and the person who expressed it. Particular attention is paid to the relationship - in terms of sequential positioning and referential extension - between reported speech, polyphony, pointing gestures and shifts in gaze direction. Data are taken from workplace management meetings that have been recorded in New Zealand by the Language in the Workplace Project