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A Branching Distributed Temporal Logic for Reasoning about Quantum State Transformations
No full textThe Distributed Temporal Logic DTL allows one to reason about temporal properties of a distributed system from the local point of view of the system's agents, which are assumed to execute independently and to interact by means of event sharing. In this paper, we introduce the Quantum Branching Distributed Temporal Logic QBDTL, a variant of DTL able to represent quantum state transformations in an abstract, qualitative way. In QBDTL, each agent represents a distinct quantum bit (the unit of quantum information theory), which evolves by means of quantum transformations and possibly interacts with other agents, and n-ary quantum operators act as communication/synchronization points between agents. We endow QBDTL with a DTL-style semantics, which fits the intrinsically distributed nature of quantum computing, we formalize a labeled deduction system for QBDTL, and we prove the soundness and completeness of this deduction system with respect to the given semantics. We give a number of examples and, finally, we discuss possible extensions of our logic in order to reason about entangle-ment phenomena
High-power, widely tunable, room-temperature picosecond optical parametric oscillator based on cylindrical 5%MgO:PPLN
No full textInternational audienceWe report a high-power picosecond optical parametric oscillator (OPO) based on cylindrical MgO:PPLN synchronously pumped by an Yb-fiber laser. The singly resonant OPO is tunable in the near-infrared signal across 1413–1900 nm and mid-infrared idler over 2418–4307 nm by angle tuning of the crystal at room temperature. With non-optimized output coupling of ∼10%, the OPO simultaneously delivers 2.4 W of signal at 1664 nm and 1.7 W of idler at 2950 nm at an overall extraction efficiency of ∼45% with high beam-pointing stability <30 μrad and <14 μrad for the signal and idler, respectively. The generated signal and idler exhibit passive power stability better than 1% rms and 0.8% rms over 15 h, respectively, in high beam quality with TEM00 profile. The extracted signal pulses from the OPO have duration of 15.2 ps with a spectral bandwidth of 0.7 nm, corresponding to a time-bandwidth product of ΔvΔtau∼1.2
The Mars Climate Database (MCD version 5.2)
No full textInternational audienceThe Mars Climate Database (MCD) is a database of meteorological fields derived from General Circulation Model (GCM) numerical simulations of the Martian atmosphere and validated using available observational data. The MCD includes complementary post-processing schemes such as high spatial resolution interpolation of environmental data and means of reconstructing the variability thereof. We have just completed (March 2015) the generation of a new version of the MCD, MCD version 5.2
Second order Pontryagin's principle for stochastic control problems
No full textWe discuss stochastic optimal control problems whose volatility does not depend on the control, and which have finitely many equality and inequality constraints on the expected value of functions of the final state, as well as control constraints. The main result is a proof of necessity of some second order optimality conditions involving Pontryagin multipliers
Equivalent Circuit Modeling for a High-Performance Large-Area Organic Photovoltaic Module
No full textInternational audienceFor organic photovoltaics (OPVs) to contribute significantly to energy generation, they need to be scaled to large areas, much like all organic electronics. Therefore, there is a need for the development of a specific model that describes the electrical properties related to the size effects and cell interconnections. We report here on the equivalent circuit models for a high-performance series-connected OPV module based on a polymer:fullerene bulkheterojunction formulation. We examine the validity of the effective single cell methodology in the conventional framework and suggest a modified model that includes the net series resistance and additional parasitic leakage conductions. The photocurrent is found to follow the diffusion-limited voltage dependence, for which an empirical treatment enables an improved reproduction of the measurement near the short-circuit point
Long Memory Through Marginalization of Large Systems and Hidden Cross-Section Dependence
No full textThis paper shows that large dimensional vector autoregressive (VAR) models of finite order can generate long memory in the marginalized univariate series. We derive high-level assumptions under which the final equation representation of a VAR(1) leads to univariate fractional white noises and verify the validity of these assumptions for two specific models. We consider the implications of our findings for the variances of asset returns where the so-called golden-rule of realized variances states that they tend always to exhibit fractional integration of a degree close to 0:4
Heavy-quark production and elliptic flow in Au + Au collisions at sNN−−−−√=62.4 GeV
No full textInternational audienceWe present measurements of electrons and positrons from the semileptonic decays of heavy-flavor hadrons at midrapidity (|y|< 0.35) in Au+Au collisions at sNN−−−−√=62.4 GeV. The data were collected in 2010 by the PHENIX experiment that included the new hadron-blind detector. The invariant yield of electrons from heavy-flavor decays is measured as a function of transverse momentum in the range 1<peT<5 GeV/c. The invariant yield per binary collision is slightly enhanced above the p+p reference in Au+Au 0%–20%, 20%–40%, and 40%–60% centralities at a comparable level. At this low beam energy this may be a result of the interplay between initial-state Cronin effects, final-state flow, and energy loss in medium. The v2 of electrons from heavy-flavor decays is nonzero when averaged between 1.3<peT<2.5 GeV/c for 0%–40% centrality collisions at sNN−−−−√=62.4 GeV. For 20%–40% centrality collisions, the v2 at sNN−−−−√=62.4 GeV is smaller than that for heavy-flavor decays at sNN−−−−√=200 GeV. The v2 of the electrons from heavy-flavor decay at the lower beam energy is also smaller than v2 for pions. Both results indicate that the heavy quarks interact with the medium formed in these collisions, but they may not be at the same level of thermalization with the medium as observed at sNN−−−−√=200 GeV
A Labelled Semantics for Soft Concurrent Constraint Programming
No full textPart 3: ConstraintsInternational audienceWe present a labelled semantics for Soft Concurrent Constraint Programming (SCCP), a language where concurrent agents may synchronize on a shared store by either posting or checking the satisfaction of (soft) constraints. SCCP generalizes the classical formalism by parametrising the constraint system over an order-enriched monoid: the monoid operator is not required to be idempotent, thus adding the same information several times may change the store. The novel operational rules are shown to offer a sound and complete co-inductive technique to prove the original equivalence over the unlabelled semantic
Speed of coming down from infinity for birth and death processes
No full text30 pagesWe finely describe the speed of "coming down from infinity" for birth and death processes which eventually become extinct. Under general assumptions on the birth and death rates, we firstly determine the behavior of the successive hitting times of large integers. We put in light two different regimes depending on whether the mean time for the process to go from to is negligible or not compared to the mean time to reach from infinity. In the first regime, the coming down from infinity is very fast and the convergence is weak.In the second regime, the coming down from infinity is gradual and a law of large numbers and a central limit theorem for the hitting times sequence hold. By an inversion procedure, we deduce that the process is a.s. equivalent to a non-increasing function when the time goes to zero. Our results are illustrated by several examples including applications to population dynamics and population genetics. The particular case where the death rate varies regularly is studied in details
Sur des problèmes de contrôle stochastique avec contraintes sur l'état
No full textThis thesis deals with Hamilton-Jacobi-Bellman (HJB) approach for some stochastic control problems in presence of state-constraints. This class of problems arises in many challenging applications, and a wide literature has already analysed such problems under some strong compatibility conditions. The main features of the present thesis is to provide new ways to face the presence of constraints without assuming any controllability condition. The first contribution of the thesis in this direction is obtained by exploiting the existing link between backward reachability and optimal control problems. It is shown that by considering a suitable auxiliary unconstrained optimal control problem, the level set approach can be extended to characterize the backward reachable sets under state-constrained. On the other hand the value function associated with a general state constrained stochastic optimal control problem is characterized by means of a state constrained backward reachable set, enabling the application of the level set method for handling the presence of the state constraints. This link between optimal control problems and reachability sets led to the theoretical and numerical analysis of HJB equations with oblique derivative boundary conditions and problems with unbounded controls. Error estimates for Markov-chain approximation represent another contribution of this manuscript. Furthermore, the properties of asymptotic controllability of a stochastic system have also been studied. A generalization of the Zubov method to state constrained stochastic systems is presented. In the last part of the thesis an ergodic optimal control problems in presence of state-constraints are considered.Cette thèse concerne l'approche Hamilton-Jacobi-Bellman (HJB) pour des problèmes de contrôle stochastique en présence de contraintes sur l'état du système. Cette classe de problèmes se pose dans de nombreuses applications importantes, et une grande littérature les a déjà analysé sous des conditions de compatibilité fortes. La principale contribution de cette thèse est de fournir de nouvelles façons de affronter la présence de contraintes sans hypothèse de contrôlabilité. La première contribution de cette thèse est obtenue en exploitant le lien existant entre l'atteignabilité des systèmes stochastiques et des problèmes de contrôle optimal. Il est montré que en considérant un problème approprié auxiliaire de la commande optimale sans contraintes sur l'état, l'approche level-set peut être étendure pour caractériser les ensembles atteignables sous contrainte sur l'état. D'autre part l'épigraphe de la fonction valeur associée à un problème général de commande optimale stochastique sous contraintes d'état peut être caractérisée par un ensemble atteignable d'un système dynamique augmenté. Ce résultat permet l'application de la méthode level-set pour gérer la présence des contraintes sur l'état sans faire d'hypothèse de contrôlabilité. Ce lien entre les problèmes de contrôle optimalet les level-set a conduit à l'analyse théorique et numérique des équations HJB avec conditions aux limites de derivé obliques et de problèmes avec contrôles non bornés. Les estimations d'erreur d'approximation de type Chaine de Markov représentent une autre contribution de ce manuscrit. En outre, les propriétés de contrôlabilité asymptotique d'un système stochastique ont également été analysées. Une généralisation de la méthode de Zubov aux systèmes stochastiques contraints est étudiée dans le manuscrit. La dernière partie de la thèse est dédié à l'étude de problèmes de contrôle optimal ergodiques en présence de contraintes sur l'état