Non-Equilibrium Statistical Mechanics of Strongly Anharmonic Chains of Oscillators

We study the model of a strongly non-linear chain of particles coupled to two heat baths at different temperatures. Our main result is the existence and uniqueness of a stationary state at all temperatures. This result extends those of Eckmann, Pillet, Rey-Bellet to potentials with essentially arbitrary growth at infinity. This extension is possible by introducing a stronger version of H\"ormander's theorem for Kolmogorov equations to vector fields with polynomially bounded coefficients on unbounded domains.Comment: ~60 pages, 3 figure

Uniqueness of the Invariant Measure for a Stochastic PDE Driven by Degenerate Noise

We consider the stochastic Ginzburg-Landau equation in a bounded domain. We assume the stochastic forcing acts only on high spatial frequencies. The low-lying frequencies are then only connected to this forcing through the non-linear (cubic) term of the Ginzburg-Landau equation. Under these assumptions, we show that the stochastic PDE has a unique invariant measure. The techniques of proof combine a controllability argument for the low-lying frequencies with an infinite dimensional version of the Malliavin calculus to show positivity and regularity of the invariant measure. This then implies the uniqueness of that measure.Comment: 45 pages, 0 figures, needs 3 latex run

Introduction : Bourdieu and the literary field

Pierre Bourdieu’s range as a thinker was extremely wide, and it would be misleading to present him primarily as a literary theorist. Trained as a philosopher, he became the leading French sociologist of his generation, and brought under the spotlight of his ‘critical sociology’ a whole series of institutional and discursive universes (education, art, linguistics, public administration, politics, philosophy, journalism, economics and others). Far from representing an intellectual dispersal, these manifold objects of enquiry allowed him to develop and refine a comprehensive theory of social process and power-relations based on distinctive concepts such as ‘field’, ‘habitus’, variously conceived notions of ‘capital’, and ‘illusio’ (all these concepts and others will be explicated and assessed in this issue). Yet Bourdieu’s analyses were scarcely ever received as neutral descriptions within the fields which he analysed. Bourdieu’s abiding agenda was to show how the discursive presuppositions and institutional logics at work in such fields carried but also masked certain social logics that a ‘critical sociology’ could disclose. Coupled with the inveterately combative drive seldom absent from Bourdieu’s objectifying analyses—and even setting aside the misprisions to which an external analyst is inevitably subject—this helps explain the resistance which his work recurrently provoked. In this respect, Bourdieu’s forays into the world of literary studies and his reception therein can be seen as part of a wider pattern

Charge Distribution on Annealed Polyelectrolytes

We investigate the equilibrium charge distribution along a single annealed polyelectrolyte chain under different conditions. The coupling between the conformation of the chain and the local charge distribution is described for various solvent qualities and salt concentration. In salt free solution, we find a slight charge depletion in the central part of the chain: the charges accumulate at the ends. The effect is less important if salt is added to the solution since the charge inhomogeneity is localized close to the chain ends over a distance of order of the Debye length. In the case of poor solvent conditions we find a different charging of beads and strings in the framework of the necklace model. This inhomogeneity leads to a charge instability and a first order transition between spherical globules and elongated chains.Comment: 20 pages, 4 figure

Towards an HLA Run-time Infrastructure with Hard Real-time Capabilities

Our work takes place in the context of the HLA standard and its application in real-time systems context. The HLA standard is inadequate for taking into consideration the different constraints involved in real-time computer systems. Many works have been invested in order to providing real-time capabilities to Run Time Infrastructures (RTI) to run real time simulation. Most of these initiatives focus on major issues including QoS guarantee, Worst Case Transit Time (WCTT) knowledge and scheduling services provided by the underlying operating systems. Even if our ultimate objective is to achieve real-time capabilities for distributed HLA federations executions, this paper describes a preliminary work focusing on achieving hard real-time properties for HLA federations running on a single computer under Linux operating systems. Our paper proposes a novel global bottom up approach for designing real-time Run time Infrastructures and a formal model for validation of uni processor to (then) distributed real-time simulation with CERTI

HP-CERTI: Towards a high performance, high availability open source RTI for composable simulations (04F-SIW-014)

Composing simulations of complex systems from already existing simulation components remains a challenging issue. Motivations for composable simulation include generation of a given federation driven by operational requirements provided "on the fly". The High Level Architecture, initially developed for designing fully distributed simulations, can be considered as an interoperability standard for composing simulations from existing components. Requirements for constructing such complex simulations are quite different from those discussed for distributed simulations. Although interoperability and reusability remain essential, both high performance and availability have also to be considered to fulfill the requirements of the end user. ONERA is currently designing a High Performance / High Availability HLA Run-time Infrastructure from its open source implementation of HLA 1.3 specifications. HP-CERTI is a software package including two main components: the first one, SHM-CERTI, provides an optimized version of CERTI based on a shared memory communication scheme; the second one, Kerrighed-CERTI, allows the deployment of CERTI through the control of the Kerrighed Single System Image operating system for clusters, currently designed by IRISA. This paper describes the design of both high performance and availability Runtime Infrastructures, focusing on the architecture of SHM-CERTI. This work is carried out in the context of the COCA (High Performance Distributed Simulation and Models Reuse) Project, sponsored by the DGA/STTC (Délégation Générale pour l'Armement/Service des Stratégies Techniques et des Technologies Communes) of the French Ministry of Defense

HLA high performance and real-time simulation studies with CERTI

Our work takes place in the context of the HLA standard and its application in real-time systems context. Indeed, current HLA standard is inadequate for taking into consideration the different constraints involved in real-time computer systems. Many works have been invested in order to provide real-time capabilities to Run Time Infrastructures (RTI). This paper describes our approach focusing on achieving hard real-time properties for HLA federations through a complete state of the art on the related domain. Our paper also proposes a global bottom up approach from basic hardware and software basic requirements to experimental tests for validation of distributed real-time simulation with CERTI