Reasoning about Knowledge and Strategies under Hierarchical Information

Two distinct semantics have been considered for knowledge in the context of strategic reasoning, depending on whether players know each other's strategy or not. The problem of distributed synthesis for epistemic temporal specifications is known to be undecidable for the latter semantics, already on systems with hierarchical information. However, for the other, uninformed semantics, the problem is decidable on such systems. In this work we generalise this result by introducing an epistemic extension of Strategy Logic with imperfect information. The semantics of knowledge operators is uninformed, and captures agents that can change observation power when they change strategies. We solve the model-checking problem on a class of "hierarchical instances", which provides a solution to a vast class of strategic problems with epistemic temporal specifications on hierarchical systems, such as distributed synthesis or rational synthesis

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

The Two Triangles: what did Wicksell and Keynes know about macroeconomics that modern economists do not (consider)?

The current consensus in macroeconomics, as represented by the New Neoclassical Synthesis, is to work within frameworks that combine intertemporal optimization, imperfect competition and sticky prices. We contrast this “NNS triangle” with a model in the spirit of Wicksell and Keynes that sets the focus on interest-rate misalignments as problems of intertemporal coordination of consumption and production plans in imperfect capital markets. We show that, with minimal deviations from the standard perfect competition model, a model structure can be derived that looks similar to the NNS triangle, but yields substantially different conclusions with regard to the dynamics of inflation and output gaps and to the design of the appropriate rule for monetary policy.

How to Handle Assumptions in Synthesis

The increased interest in reactive synthesis over the last decade has led to many improved solutions but also to many new questions. In this paper, we discuss the question of how to deal with assumptions on environment behavior. We present four goals that we think should be met and review several different possibilities that have been proposed. We argue that each of them falls short in at least one aspect.Comment: In Proceedings SYNT 2014, arXiv:1407.493

Games on graphs with a public signal monitoring

We study pure Nash equilibria in games on graphs with an imperfect monitoring based on a public signal. In such games, deviations and players responsible for those deviations can be hard to detect and track. We propose a generic epistemic game abstraction, which conveniently allows to represent the knowledge of the players about these deviations, and give a characterization of Nash equilibria in terms of winning strategies in the abstraction. We then use the abstraction to develop algorithms for some payoff functions.Comment: 28 page

Getting rid of Keynes ? A survey of the history of macroeconomics from Keynes to Lucas and beyond

The aim of this paper is to recount the ebbs and flows of Keynesianism over the history of macroeconomics. The bulk of the paper consists of a discussion of the main episodes of the unfolding of macroeconomics (Keynesian macroeconomics, monetarism, new classical macroeconomics, real business cycle models and new neoclassical synthesis models) against the background of a distinction between Keynesianism as a ‘moderately conservative’ (Keynes’s words) vision about the working of the market system and as a conceptual apparatus. Particular attention is given to the contrast between Keynesian and Lucasian macroeconomics. The paper ends with a few remarks about the impact of the present crisis on the development of macroeconomic theoryKeynes, Lucas, history of macroeconomics

Computing Weakest Strategies for Safety Games of Imperfect Information

CEDAR (Counter Example Driven Antichain Refinement) is a new symbolic algorithm for computing weakest strategies for safety games of imperfect information. The algorithm computes a fixed point over the lattice of contravariant antichains. Here contravariant antichains are antichains over pairs consisting of an information set and an allow set representing the associated move. We demonstrate how the richer structure of contravariant antichains for representing antitone functions, as opposed to standard antichains for representing sets of downward closed sets, allows CEDAR to apply a significantly less complex controllable predecessor step than previous algorithms

Back to Keynes?

After a brief review of classical, Keynesian, New Classical and New Keynesian theories of macroeconomic policy, we assess whether New Keynesian Economics captures the quintessential features stressed by J.M. Keynes. Particular attention is paid to Keynesian features omitted in New Keynesian workhorses such as the micro-founded Keynesian multiplier and the New Keynesian Phillips curve. These theories capture wage and price sluggishness and aggregate demand externalities by departing from a competitive framework and give a key role to expectations. The main deficiencies, however, are the inability to predict a pro-cyclical real wage in the face of demand shocks, the absence of inventories, credit constraints and bankruptcies in explaining the business cycle, and no effect of the nominal as well as the real interest rate on aggregate demand. Furthermore, they fail to allow for quantity rationing and to model unemployment as a catastrophic event. The macroeconomics based on the New Keynesian Phillips curve has quite a way to go before the quintessential Keynesian features are captured.Keynesian economics, New Keynesian Phillips curve, monopolistic competition, nominal wage rigidity, welfare, pro-cyclical real wage, inventories, liquidity, bankruptcy, unemployment, monetary policy

The New Keynesian Approach to Business Cycle Theory: Nominal and Real Rigidities

At the heart of the Neoclassical synthesis lies the assumption that prices do not adjust instantly to equilibrate supply and demand. Under these circumstances, once the synthesis failed, economists naturally started to investigate whether the imperfect adjustment of prices could be logically inferred from realistic assumptions regarding the microeconomic environment, and subsequent research led to a variety of new non-walrasian theories regarding the functioning of markets. Thus, the non-walrasian analyses of the labour market suggested that wages could perform other functions than to equilibrate labour supply and demand. For instance, in models focused on labour contracts, wages are regarded as an „insurance” provided by the employer to the workers, while in efficiency wage models, wages are determinants of labour productivity. Such models have the ability to account for unemployment, but they are not able to explain the failure of the classical dichotomy. The paper aims to investigate the theoretical progress achieved during the past 3 decades, to clarify nominal and real rigidities and evaluate their impact on the business cycle and finally, to evaluate the theoretical aspects which need further analyses and refinements.nominal rigidities, real rigidities, menu costs, efficiency wages, near rationality.