Quantitative games with interval objectives

Traditionally quantitative games such as mean-payoff games and discount sum games have two players -- one trying to maximize the payoff, the other trying to minimize it. The associated decision problem, "Can Eve (the maximizer) achieve, for example, a positive payoff?" can be thought of as one player trying to attain a payoff in the interval $(0,\infty)$. In this paper we consider the more general problem of determining if a player can attain a payoff in a finite union of arbitrary intervals for various payoff functions (liminf, mean-payoff, discount sum, total sum). In particular this includes the interesting exact-value problem, "Can Eve achieve a payoff of exactly (e.g.) 0?"Comment: Full version of CONCUR submissio

Looking at Mean-Payoff through Foggy Windows

Mean-payoff games (MPGs) are infinite duration two-player zero-sum games played on weighted graphs. Under the hypothesis of perfect information, they admit memoryless optimal strategies for both players and can be solved in NP-intersect-coNP. MPGs are suitable quantitative models for open reactive systems. However, in this context the assumption of perfect information is not always realistic. For the partial-observation case, the problem that asks if the first player has an observation-based winning strategy that enforces a given threshold on the mean-payoff, is undecidable. In this paper, we study the window mean-payoff objectives that were introduced recently as an alternative to the classical mean-payoff objectives. We show that, in sharp contrast to the classical mean-payoff objectives, some of the window mean-payoff objectives are decidable in games with partial-observation

Linear elastic fracture mechanics predicts the propagation distance of frictional slip

When a frictional interface is subject to a localized shear load, it is often (experimentally) observed that local slip events initiate at the stress concentration and propagate over parts of the interface by arresting naturally before reaching the edge. We develop a theoretical model based on linear elastic fracture mechanics to describe the propagation of such precursory slip. The model's prediction of precursor lengths as a function of external load is in good quantitative agreement with laboratory experiments as well as with dynamic simulations, and provides thereby evidence to recognize frictional slip as a fracture phenomenon. We show that predicted precursor lengths depend, within given uncertainty ranges, mainly on the kinetic friction coefficient, and only weakly on other interface and material parameters. By simplifying the fracture mechanics model we also reveal sources for the observed non-linearity in the growth of precursor lengths as a function of the applied force. The discrete nature of precursors as well as the shear tractions caused by frustrated Poisson's expansion are found to be the dominant factors. Finally, we apply our model to a different, symmetric set-up and provide a prediction of the propagation distance of frictional slip for future experiments

Short Note on the Unemployment Rate of the “French overseas regionsâ€

This article analyzes the hysteresis hypothesis in the unemployment rates of the four “French overseas regions†(Guadeloupe, Martinique, Guyana, Reunion) [FORs] over the period 1993-2008. We use standard univariate and panel unit root tests, among them Choi (2006) and Lopez (2009) that account for cross-sectional dependence and have improved performance when the number of countries and the time dimension of the data are limited. Our results cannot reject the null hypothesis of a unit root and so find evidence supporting hysteresis in the unemployment rates for the FORs.Hysteresis, Unemployment, Panel unit root test, cross-section dependence, convergence

The commitment of sheep and goat production systems in the agro-ecological transition:a collective participative approach in Corsica

OM 123The importance of environmental challenges in agriculture and livestock production requires an eco-logical transition of the production systems including the sheep and goat ones. In this context, establishing theconditions for agro – ecological changes and building innovative pathways of changes could favor this transi-tion. After a presentation of some theoretical concepts behind the idea of ecological transition and agro – ecol-ogy, the objective of this communication is to report the implementation of a participative approach involvingscientists, technicians, teachers and breeders in Corsica Island focusing on pastoral systems. This approachaims to design the performances of the systems from their triple social economic and environmental dimen-sions, how they are in line with the agro – ecological orientations and how to improve them. Inspired from pre-vious methodologies but innovating through a participative approach, an easy-to-implement method has beenadjusted to the characteristics of the local systems and agro-ecological criteria for sheep and goat herds andsystems, we designed 10 groups of indicators including societal dimensions integrated in an AgroecologicalLivestock Proximity Index (ALPI). The exchanges during the sessions have shown that agro-ecology is notonly an institutional injunction. It is also a collective methodological approach and pathway to design whichinnovations could support the sustainable development and changes in sheep and goat farming and special-ly, in pastoral systems. The utilization of this method and its further developments are evoked

Measuring the Sustainability of Cities: A Survey-Based Analysis of the Use of Local Indicators

We analyze 17 studies of the use of sustainable development indicators (SDI) in an urban setting. The analysis reveals a lack of consensus not only on the conceptual framework and the approach favored, but also on the selection and optimal number of indicators. First, by performing different classifications and categorizations of SDI we identify problems inherent in territorial practices that use SDI. Second, we argue that the lack of consensus in several steps of the creation of SDI stems notably from the ambiguity in the definitions of sustainable development, objectives for the use of such indicators, the selection method and the accessibility of qualitative and quantitative data. Third, we propose a selection strategy for SDI through which we demonstrate the need to adopt a parsimonious list of SDI covering the sustainable development components and their constituent categories as broadly as possible while minimizing the number of indicators retained. Nous analysons 17 études traitant de l’utilisation d’indicateurs de développement durable (IDD) en milieu urbain pour différents pays, provinces ou états occidentaux. 188 IDD différents sont recensés dans ces études dont 135 (72 %) ne sont utilisés qu’une ou deux fois. L’analyse de ces études révèle ainsi un faible consensus non seulement au niveau du cadre conceptuel ou de l’approche préconisée, mais aussi en ce qui concerne la sélection et le nombre d’indicateurs optimal. Premièrement, différents classements et catégorisations des IDD recensés nous permettent d’observer et d’identifier les problèmes inhérents aux pratiques territoriales ayant recours aux IDD. Deuxièmement, nous argumentons que l’absence de consensus à plusieurs étapes de la création des IDD émergent entre autres de l’ambiguïté occasionnée par la définition du développement durable, des objectifs visées par l’utilisation de tels indicateurs, de la méthode de sélection préconisée et de l’accessibilité des données qualitatives et quantitatives en cette matière. Troisièmement, nous proposons une stratégie de sélection des IDD (que nous appelons SuBSeleC) où nous démontrons la nécessité d’adoption d’une liste parcimonieuse d’IDD couvrant le plus largement possible les volets du développement durable et des catégories qui les composent tout en minimisant le nombre d’indicateurs retenus. Le résultat est une liste concise et moins redondante d’indicateurs moins sectoriels et plus intégrateurs ayant l’avantage d’englober les dimensions intégrées du développement durable.Cities, Indicators, Sustainable Development, Environment, Local Governance., Villes, indicateurs, développement durable, environnement, gouvernance locale.