Uniform Strategies

We consider turn-based game arenas for which we investigate uniformity properties of strategies. These properties involve bundles of plays, that arise from some semantical motive. Typically, we can represent constraints on allowed strategies, such as being observation-based. We propose a formal language to specify uniformity properties and demonstrate its relevance by rephrasing various known problems from the literature. Note that the ability to correlate different plays cannot be achieved by any branching-time logic if not equipped with an additional modality, so-called R in this contribution. We also study an automated procedure to synthesize strategies subject to a uniformity property, which strictly extends existing results based on, say standard temporal logics. We exhibit a generic solution for the synthesis problem provided the bundles of plays rely on any binary relation definable by a finite state transducer. This solution yields a non-elementary procedure.Comment: (2012

The Complexity of Synthesizing Uniform Strategies

We investigate uniformity properties of strategies. These properties involve sets of plays in order to express useful constraints on strategies that are not \mu-calculus definable. Typically, we can state that a strategy is observation-based. We propose a formal language to specify uniformity properties, interpreted over two-player turn-based arenas equipped with a binary relation between plays. This way, we capture e.g. games with winning conditions expressible in epistemic temporal logic, whose underlying equivalence relation between plays reflects the observational capabilities of agents (for example, synchronous perfect recall). Our framework naturally generalizes many other situations from the literature. We establish that the problem of synthesizing strategies under uniformity constraints based on regular binary relations between plays is non-elementary complete.Comment: In Proceedings SR 2013, arXiv:1303.007

Automata Techniques for Epistemic Protocol Synthesis

International audienceIn this work we aim at applying automata techniques to problems studied in Dynamic Epistemic Logic, such as epistemic planning. To do so, we first remark that repeatedly executing ad infinitum a propositional event model from an initial epistemic model yields a relational structure that can be finitely represented with automata. This correspondence, together with recent results on uniform strategies, allows us to give an alternative decidability proof of the epistemic planning problem for propositional events, with as by-products accurate upper-bounds on its time complexity, and the possibility to synthesize a finite word automaton that describes the set of all solution plans. In fact, using automata techniques enables us to solve a much more general problem, that we introduce and call epistemic protocol synthesis

Folie, théâtre et politique dans Caligula d'Albert Camus

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal

Colour maps for fisheries acoustic echograms

Echograms are used to visualize fisheries acoustic data, but choice of colour map has a significant effect on appearance. Quantitative echograms should use colour maps, which are colourful (have a perceived variety and intensity of colours), sequential (have monotonic lightness), and perceptually uniform (have consistency of perceived colour contrast over their range). We measure whether colour maps are colourful (⁠Mˆ(3)>0⁠), sequential (⁠rs=±1⁠), and perceptually uniform (ρ = 1) using an approximately perceptually uniform colour space (CIELAB). Whilst all the fisheries acoustic colour maps tested are colourful, none is sequential or perceptually uniform. The widely used EK500 colour map is extremely colourful (⁠Mˆ(3)=186⁠), not sequential (⁠rs=0.06⁠), and has highly uneven perceptual contrast over its range (⁠ρ=0.26⁠). Of the fisheries acoustic colour maps tested, the Large Scale Survey System default colour map is least colourful (⁠Mˆ(3)=79⁠), but comes closest to being sequential (⁠rs=−0.94⁠), and perceptually uniform (⁠ρ=0.95⁠). Modern colour maps have been specifically designed for colour contrast consistency, accessibility for viewers with red-green colour-blindness, and legibility when printed in monochrome, and may be better suited to the presentation and interpretation of quantitative fisheries acoustic echograms

Coherence-enhanced, phase-dependent dissipation in long SNS Josephson junctions: revealing Andreev Bound States dynamics

One of the best known causes of dissipation in ac driven quantum systems stems from photon absorption. Dissipation can also be caused by the retarded response to the time-dependent excitation, and in general gives insight into the system's relaxation times and mechanisms. We address the dissipation in a mesoscopic normal wire with superconducting contacts, that sustains a supercurrent at zero frequency and that may be expected to remain dissipationless at frequency lower than the superconducting gap. We probe the high frequency linear response of a Normal/Superconductor ring to a time-dependent flux by coupling it to a highly sensitive multimode microwave resonator. Far from being the simple derivative of the current-phase relation, the ring's ac susceptibility also displays a dissipative component whose phase dependence is a signature of the dynamical processes occurring within the Andreev spectrum. We show how dissipation is driven by the competition between the two aforementioned mechanisms. Depending on the relative strength of those contributions, dissipation can be maximal at $\pi$, when the minigap closes, or can be maximal near $\pi/2$, when the dc supercurrent is maximal. We also find that the dissipative response increases at low temperature and can even exceed the normal state conductance. The results are confronted with predictions of the Kubo linear response and time-dependent Usadel equations. This experiment shows the power of the ac susceptibility measurement of individual hybrid mesoscopic systems in probing in a controlled way the quantum dynamics of ABS. By spanning different physical regimes, our experiments provide a unique access to inelastic scattering and spectroscopy of an isolated quantum coherent system. This technique should be a tool of choice to investigate topological superconductivity and detect the topological protection of edge states

Opacity Issues in Games with Imperfect Information

We study in depth the class of games with opacity condition, which are two-player games with imperfect information in which one of the players only has imperfect information, and where the winning condition relies on the information he has along the play. Those games are relevant for security aspects of computing systems: a play is opaque whenever the player who has imperfect information never "knows'' for sure that the current position is one of the distinguished "secret'' positions. We study the problems of deciding the existence of a winning strategy for each player, and we call them the opacity-violate problem and the opacity-guarantee problem. Focusing on the player with perfect information is new in the field of games with imperfect-information because when considering classical winning conditions it amounts to solving the underlying perfect-information game. We establish the EXPTIME-completeness of both above-mentioned problems, showing that our winning condition brings a gap of complexity for the player with perfect information, and we exhibit the relevant opacity-verify problem, which noticeably generalizes approaches considered in the literature for opacity analysis in discrete-event systems. In the case of blindfold games, this problem relates to the two initial ones, yielding the determinacy of blindfold games with opacity condition and their PSPACE-completeness.Nous étudions en détail la classe des jeux à condition d'opacité, qui sont des jeux à deux joueurs à information imparfaite dans lesquels seul l'un des joueurs n'a pas information parfaite, et où la condition de gain dépend de l'information que celui-ci a au cours du jeu. Ces jeux sont liés à des aspects de sécurité des systèmes informatiques : une partie est opaque si le joueur à information imparfaite ne "sait" jamais avec certitude que la position courante est l'une des positions spéciales dites "secrètes". Nous étudions les problèmes de décision d'existence de stratégie gagnante pour chaque joueur, et nous les appellons opacity-violate problem et opacity-guarantee problem. Le fait de s'intéresser au joueur à information parfaite est nouveau en théorie des jeux à information imparfaite car lorsqu'on considère des conditions de gain classiques cela revient à considérer le jeu à information parfaite sous-jacent. Nous établissons que les deux problèmes sus-mentionnés sont EXPTIME-complets, montrant ainsi que notre condition de gain apporte un saut de complexité pour le joueur à information parfaite, et nous exhibons le problème opacity-verify qui, de manière intéressante, généralise des approches considérées dans la littérature pour l'analyse d'opacité des systèmes à événements discrets. Dans le cas des jeux en aveugle, ce problème se relie aux deux problèmes initiaux, de telle sorte que les jeux en aveugle à condition d'opacité sont déterminés et que les trois problèmes sont PSPACE-complets