Cheap Talk, Gullibility, and Welfare in an Environmental Taxation Game

We consider a simple dynamic model of environmental taxation that exhibits time inconsistency. There are two categories of firms, Believers, who take the tax announcements made by the Regulator to face value, and Non-Believers, who perfectly anticipate the Regulator's decisions, albeit at a cost. The proportion of Believers and Non- Believers changes over time depending on the relative profits of both groups. We show that the Regulator can use misleading tax announcements to steer the economy to an equilibrium that is Pareto superior to the solutions usually suggested in the literature. Depending upon the initial proportion of Believers, the Regulator may prefer a fast or a low speed of reaction of the firms to differences in Believers/Non-Believers profits.Environmental policy, Emissions taxes, Time inconsistency, Heterogeneous agents, Bounded rationality, Learning, Multiple equilibria, Stackelberg games

GAMES AND STRATEGIES IN ANALYSIS OF SECURITY PROPERTIES

Information security problems typically involve decision makers who choose and adjust their behaviors in the interaction with each other in order to achieve their goals. Consequently, game theoretic models can potentially be a suitable tool for better understanding the challenges that the interaction of participants in information security scenarios bring about. In this dissertation, we employ models and concepts of game theory to study a number of subjects in the field of information security. In the first part, we take a game-theoretic approach to the matter of preventing coercion in elections. Our game models for the election involve an honest election authority that chooses between various protection methods with different levels of resistance and different implementation costs. By analysing these games, it turns out that the society is better off if the security policy is publicly announced, and the authorities commit to it. Our focus in the second part is on the property of noninterference in information flow security. Noninterference is a property that captures confidentiality of actions executed by a given process. However, the property is hard to guarantee in realistic scenarios. We show that the security of a system can be seen as an interplay between functionality requirements and the strategies adopted by users, and based on this we propose a weaker notion of noninterference, which we call strategic noninterference. We also give a characterisation of strategic noninterference through unwinding relations for specific subclasses of goals and for the simplified setting where a strategy is given as a parameter. In the third part, we study the security of information flow based on the consequences of information leakage to the adversary. Models of information flow security commonly prevent any information leakage, regardless of how grave or harmless the consequences the leakage can be. Even in models where each piece of information is classified as either sensitive or insensitive, the classification is “hardwired” and given as a parameter of the analysis, rather than derived from more fundamental features of the system. We suggest that information security is not a goal in itself, but rather a means of preventing potential attackers from compromising the correct behavior of the system. To formalize this, we first show how two information flows can be compared by looking at the adversary’s ability to harm the system. Then, we propose that the information flow in a system is effectively secure if it is as good as its idealized variant based on the classical notion of noninterference. Finally, we shift our focus to the strategic aspect of information security in voting procedures. We argue that the notions of receipt-freeness and coercion resistance are underpinned by existence (or nonexistence) of a suitable strategy for some participants of the voting process. In order toback the argument formally, we provide logical “transcriptions” of the informal intuitions behind coercion-related properties that can be found in the existing literature. The transcriptions are formulatedin the modal game logic ATL*, well known in the area of multi-agent systems

Game Theory Relaunched

The game is on. Do you know how to play? Game theory sets out to explore what can be said about making decisions which go beyond accepting the rules of a game. Since 1942, a well elaborated mathematical apparatus has been developed to do so; but there is more. During the last three decades game theoretic reasoning has popped up in many other fields as well - from engineering to biology and psychology. New simulation tools and network analysis have made game theory omnipresent these days. This book collects recent research papers in game theory, which come from diverse scientific communities all across the world; they combine many different fields like economics, politics, history, engineering, mathematics, physics, and psychology. All of them have as a common denominator some method of game theory. Enjoy

Strategic logics : complexity, completeness and expressivity

by transferring normative attributes from an agent to another. Such interactions are called delegation. Formal models of delegation and control were studied in, e.g., [189, 149, 191]. In this work, we consider the scenario where agents delegate control over propositions to other agents. The distinction between controllable and uncontrollable propositions stems from areas like discrete event systems and control theory, where, e.g., Boutilier [39] studied control in the context of deontic logic. Control and controllable propositions were also studied in [52, 66, 249, 248]. We now give an overview of the thesis. The main purpose of Chapter 2 is to introduce basic concepts and notation and to review relevant literature. The first section presents a brief survey on modal logic. Then, in sections 2.2, 2.3 and 2.4, we introduce epistemic, temporal and strategic modal logics and state known results that characterise their expressivity and computational complexity. In particular, we consider variants of ATL as extensions of branching-time logics. With such ATL-like logics we can describe dynamic multi-agent interactions. In Section 2.5, we discuss extensions of ATL with epistemic notions. Additionally, we suggest a framework for memory-bounded strategic reasoning. In particular, we introduce an epistemic variant of ATL that accounts for agents with limited memory resources as this case was neglected in the literature to date. In Chapter 3, we investigate the computational complexity of ATL and its epistemic extension ATEL. We show in detail how 'the complexity of the satisfiability problem for both logics can be settled at ExpTIME-complete. The part of the chapter about ATL is based on the paper 'ATL Satisfiability is Indeed ExpTIME-COmplete' by Walther, Lutz, Wolter and Wooldridge in the Journal of Logic and Computation, 2006 (265)' and the part about ATEL is based on the paper 'ATEL with Common and Distributed Knowledge is ExpTime-Complete' by Walther which was presented at the 4th Workshop on Methods for Modalities, Humbolt University, Berlin, December 1-2, 2005 [264]. In Chapter 4, we aim to extend the expressiveness of ATL without increasing its computational complexity. We introduce explicit names for strategies in the object language and extend modal operators with the possibility to bind agents to strategy names. In this way, we can fix the decisions of agents that possibly belong to several coalitions. By identifying the behaviqur of agents, we can reason about the effects of agents changing coalitions. Dynamic coalitions provide more flexibility to adapt abilities to a changing environment. We investigate the expressivity of the resulting logic ATLES and compare it to ATL and ATL*. Moreover, we formulate two model checking problems for ATLES and investigate their complexity as well as the complexity of the satisfiability problem for ATLES. Additionally, we present a complete axiomatisation. This chapter is based on the paper 'Alternating-time Temporal Logic with Explicit Strategies' by Walther, van der Hoek and Wooldridge which is going to presented at the 11th Conference on Theoretical Aspects of Rationality and Knowledge (TARK), Brussels, Belgium, June 25-27, 2007 [266]

COIN@AAMAS2015

COIN@AAMAS2015 is the nineteenth edition of the series and the fourteen papers included in these proceedings demonstrate the vitality of the community and will provide the grounds for a solid workshop program and what we expect will be a most enjoyable and enriching debate.Peer reviewe

The efficacy of third-party interventions: international organization-led interventions into ongoing and post-conflict situations

The past 30 years have seen the international system undergo definite change in both the nature of conflict and the way in which it is responded to by international actors. Interstate wars have largely given way to civil conflicts, which have themselves arguably changed in character over the last few decades. International responses have turned towards third-party military interventions; although not a new expression of force, the rules upon which these interventions are based have changed, and so correspondingly have their form and targets. These military incursions by states, coalitions, and International Organizations (IOs) external to the conflict have taken on a new importance, an increasingly multilateral character, and a (nominally and truly) humanitarian bent. This increasing prevalence in IO-led interventions in particular has tapered off slightly since its peak in the 2000s, but the persistence of these missions around the world speaks volumes of their continued importance. Since the conditions prompting intervention have not been eradicated, and states and IOs still appear to be invested in intervening in these situations, understanding what a successful outcome looks like and what factors influence the effectiveness of these interventions is a task that holds not only theoretical but also practical value. This dissertation contributes to this strand of literature by explicitly theorizing about what effective means, introducing the explanatory variable level of formalization, and incorporating multiple IOs into a single analysis. Because the time horizons of an intervention into an ongoing conflict and a post-conflict situation are different, the measures of what makes an intervention "effective" and the factors influencing its effectiveness will also necessarily be different. Ongoing conflicts have shorter, more urgent time frames and shorter-term goals: reducing civilian casualties and achieving victory for whichever side is supported if the intervention in biased. Post-conflict situations have less urgent time frames and longer-term goals: rebuilding physical and political/social infrastructure. Fulfilling the mission's mandate applies to both ongoing and post-conflict missions. The level of formalization of an IO varies based on the unity and clarity of the mission's command and control structures, the severity of national caveats, and the number and integration of troop-contributing countries. Essentially, higher formalization shows a unity of effort that means the IO is able to effectively utilize the resources at its disposal to create a mission that is more than the sum of its parts. Greater levels of formalization increase the likelihood of the intervention achieving its goals, the ability to quickly and decisively determine where resources are best applied and move those resources where they are needed increases the mission's ability to reduce civilian casualties, help a chosen side achieve victory, fulfill its mandates, and rebuild the host state's infrastructure. To fully develop and test this theory, this dissertation uses a mixed-methods approach, first presenting a quantitative analysis that operationalizes the key concepts and explores through simple and multiple regression the relationship between a mission's level of formalization and to what extent it achieves its goals. This time-series cross-sectional analysis shows promise, but necessitates further research. To that end, the following chapters are case studies of interventions into Bosnia-Herzegovina in the early 1990s and Kosovo starting in the late 1990s respectively. Tracing each UN, NATO, and EU mission's level of formalization across its lifespan and how that relates to the mission's outcomes is one benefit of utilizing case study research, and in this instance, shows more clearly and in greater detail how higher levels of formalization increase a mission's ability to achieve its goals, while lower levels of formalization can make a mission less effective.Includes bibliographical references

Proceedings of The Multi-Agent Logics, Languages, and Organisations Federated Workshops (MALLOW 2010)

http://ceur-ws.org/Vol-627/allproceedings.pdfInternational audienceMALLOW-2010 is a third edition of a series initiated in 2007 in Durham, and pursued in 2009 in Turin. The objective, as initially stated, is to "provide a venue where: the cost of participation was minimum; participants were able to attend various workshops, so fostering collaboration and cross-fertilization; there was a friendly atmosphere and plenty of time for networking, by maximizing the time participants spent together"