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Invited Speakers 

Invited Speaker 
Talk 
Roko Aliprantis Purdue University aliprantismgmt.purdue.edu 
Some applications of Riesz spaces to Economics, Finance, and Econometrics The mathematical theory of Riesz spaces (vector lattices) has been found to be very useful in many applied problems and optimization theory. In this general talk, we shall present several applications of Riesz spaces to economics, finance, and econometrics. The emphasis will be on the role of the lattice properties of Riesz spaces in these areas. 
Robert Aumann Hebrew University of Jerusalem raumannmath.huji.ac.il 
Assessing Strategic Risk [PDF]  joint work with Jacques H. Dreze In recent decades, the concept of subjective probability has been increasingly applied to an adversary's choices in strategic games. A careful examination reveals that the standard construction of subjective probabilities does not apply in this context. We show how the difficulty may be overcome by means of a different construction. 
Steven Brams New York University steven.bramsnyu.edu 
A Minimax Procedure for Electing Committees [PDF]  joint work with D. Marc Kilgour and M. Remzi Sanver A procedure for electing committees, called the minimax
procedure, is described. While based on approval voting (AV), it
chooses the committee that minimizes the maximum "Hamming distance" to
all voters (minimax outcome). Such an outcome may be diametrically
opposed to the usual AV outcome, which minimizes the sum of the Hamming
distances to all voters (minisum outcome). Computer simulation is used
to determine how much, on average, minimax and minisum outcomes
diverge. The manipulability of the minimax procedure is also
investigated. 
Stefano Demichelis University of Pavia stefanodnetcomp.it 
On some (mis)applications of topology to game theory The theory of nash equilibria is, formally, that of fixed points of continuous functions and correspondences, so it is not surprising that some properties of the latter are relevant to strategic behaviour. In my talk I will show how some elementary algebraic topological facts have can shed light on the relation between the different stability concepts, I shall also discuss more promising approaches to the analysis of strategic behaviour. 
Daniel Diermeier Northwestern University ddiermeierkellogg.northwestern.edu 
The talk will discuss recent applications of noncooperative gametheory and structural estimation techniques to study the design of political constitutions. 
Peter Eso Northwestern University esokellogg.northwestern.edu 
Information Disclosure in Auctions  joint work with Balazs Szentes We analyze a situation where a monopolist is selling an indivisible good to risk neutral buyers who only have an estimate of their private valuations. The seller can release, without observing, certain additional signals, which affect the buyers’ valuations. Our main result is that in the expected revenue maximizing mechanism, the seller makes available all the information that she can, and her expected revenue is the same as it would be if she could observe the released signals. We also show that this mechanism can be implemented by what we call a “handicap auction” in interesting applications (including one where the additional signal resolves an additive risk in the buyers’ valuations). In the first round of this auction, each buyer picks a price premium from a menu published by the seller (a smaller premium costs more). Then the seller releases the additional signals. In the second round, the buyers compete in a secondprice auction where the winner pays the sum of his premium and the second highest nonnegative bid. 
Arieh Gavious University of Toronto ariehgrotman.utoronto.ca 
Asymptotic Analysis of Large Auctions [PDF]  joint work with Gadi Fibich and Aner Sela We study privatevalue auctions with a large number of bidders. We first calculate asymptotic approximations of the equilibrium bids and the seller's revenue in firstprice auctions, regardless of whether the bidders are symmetric or asymmetric, riskneutral or risk averse. We then show that with n bidders, the effects of risk aversion and of asymmetry on the equilibrium bids and on the seller's revenue are only O(1/n^2). Furthermore, it is demonstrated that firstprice auctions with asymmetric bidders or with risk averse bidders are O(1/n^2) revenue equivalent to large classes of standard auctions. 
John Geanakoplos Yale University john.geanakoplosyale.edu 
Incentives in Games of Status: 100,99,...,1 or A,B,C? [PDF]  joint work with Pradeep Dubey We show that if students care primarily about their status (relative rank) in class, they are best motivated to work not by revealing their exact numerical exam scores (100,99,...,1), but instead by clumping them in broad categories (A,B,C). If their abilities are disparate, the optimal grading scheme awards fewer A's than there are alphaquality students, creating small elites. If their abilities are common knowledge, then it is better to grade them on an absolute scale (100 to 90 is an A, etc.) rather than on a curve (top 15% is an A, etc.). We develop criteria for optimal grading schemes in terms of the stochastic dominance between student performances. 
Olivier Gossner CERAS Olivier.Gossnermail.enpc.fr 
Incentives to innovation activities are tied to the value of
information. In general, private benefits and social benefits to more
information are not equal. Arrow (1962) shows that the private value of
invention can be lower than its social value, which results in
underinvestment in innovation activities. Hirshleifer (1971) exhibits
situations where private value of information is positive whereas
social value is null, which can result in overivestment in research, as
well as situations in which private value for information is negative. 
John Hillas University of Auckland j.hillasauckland.ac.nz 
On the relation between backward and forward induction We consider the relation between forward and backward induction. An example shows that a strong relation, previously conjectured by one of the authors, is incorrect. Two weaker results, one restricting attention to two player games and one weakening the notion of forward induction, are shown. 
Sergei Izmalkov MIT izmalkovMIT.EDU 
Shillbidding and optimal auctions A single object is for sale to N asymmetric buyers in the
independent private values setting by means of an English auction. We
consider implications of seller's active participation in the bidding
process, or shill bidding. Our main result is that the English auction
with shill bidding has an equilibrium that is outcome equivalent to the
optimal mechanism of Myerson (1981). Thus, not only the optimal auction
can be implemented by a detailedfree mechanism, this is done by the
most common of auction forms. 
Ehud Kalai Northwestern University kalaikellogg.northwestern.edu 
Extensive Robustness Revisited Being extensively robust means that an equilibrium of a
simultaneous move game G survives even if the simultaneous move
assumption is relaxed (e.g., it allows for variations in the order of
moves, information leakage, revisions, commitments, control over
opponents’ moves, cheaptalk announcements etc.). In a recent paper the
author shows that the equilibria of games with many semi anonymous
players are extensively robust. 
Vijay Krishna Penn State University vkrishnapsu.edu 
Mechanism Design under Imperfect Commitment Mechanism design theory rests on the assumption that the designer can commit tothat is, contract onthe workings of the mechanism. In practice, the power or willingness to commit is rarely absolute and in its absence many insights of mechanism design theory are no longer valid. For instance, the celebrated revelation principle no longer holds. We investigate a model of optimal contracting between an uninformed principal and an informed agent where the principal's commitment power is imperfectwhile the principal can contract on the agent's compensation, he is unable to, or unwilling to, contract on other decisions. As a first step, we establish a limited revelation principle that applies in this context . We then exhibit some features of the optimal contractwhile full alignment of interests combined with delegation of authority is feasible, it is never optimal. The optimal contract is "bangbang"in one region of the state space, full alignment takes place, in the the other, no alignment takes place. These contracts are then to those in which the principal has full commitment power as well as to several "informal" institutional arrangements. 
Michael Maschler Hebrew University of Jerusalem maschlervms.huji.ac.il 
Applying the Reduced Game Property to Analyze Cores and Nucleoli of Various Enterprizes [PDF] Cooperative game theory faces two serious problem whenever
there is a need to apply it: 
Wojciech Olegewski Northwestern University wonorthwestern.edu 
The Folk Theorem for All Games with Almost Perfect Monitoring  joint work with Johannes Horner We study repeated games in which monitoring is private. We prove the folk theorem for all twoplayer games assuming that the monitoring is almost perfect, but not necessarily almost public. 
Thomas Palfrey CalTech trphss.caltech.edu 
SelfCorrecting Information Cascades [PDF]  joint work with Jacob Goeree, Brian Rogers, and Richard McKelvey In laboratory experiments, information cascades are ephemeral
phenomena, collapsing soon after they form, and then 
Jerome Renault CEREMADE, University Paris 9 renaultceremade.dauphine.fr 
Multicast communication in networks: reliability and security of information transmission  joint work with T. Tomala This work takes place in the general context of strategic transmission of information. We concentrate on a simple model of multicast communication, where the players are distant nodes in some network modelled by a graph, and player a (the sender) wants to send some information to player b (the receiver). The network is said to be Treliable if no malevolent adversary controlling T nodes can prevent player a to send some information to player b. It is said to be Tsecure if no malevolent adversary controlling T nodes can prevent player a to send privately some information to player b. Reliability and security are studied, and a few links with the existence of equilibria in repeated games with incomplete information, and with computer science problems are presented. 
Andrew Schotter New York University andrew.schotternyu.edu 
We present an intergenerational version of the Van Huyck et al.'s (1990) Minimum Game. 8 subjects play the game for 10 periods. Afterwards each participant is replaced by another agent, his laboratory descendent, who then plays the game for another 10 periods with a group of new subjects. The generations are nonoverlapping. Advice from a member of one generation is passed along to his successor via freeform messages that generation t players leave for their generation t+1 successors. It was our conjecture that using such an intergenerational design subjects would be able to "talk themselves to efficiency" in the sense of converging to the payoffdominant outcome. What we find is that there is a quality threshold with advice. If the advice offered to subjects is sufficiently strong in urging them to cooperate then as long as that advice is offered in a public manner (either as common knowledge or as what we call "almost common knowledge") we can expect cooperation to follow. However, if the advice quality is below a threshold then cooperation is likely to result only if the advice is not only public but also distributed in a manner that makes it common knowledge. 
Lloyd Shapley UCLA . 
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Sylvain Sorin U. Pierre et Marie Curie sorinmath.jussieu.fr 
Differential inclusions, stochastic approximations and dynamics in games [PDF]  joint work with M. Benaim and J. Hofbauer The dynamical systems approach to stochastic approximation is
generalized to the case where the mean differential equation is
replaced by a differential inclusion. 
William Sudderth University of Minnesota billstat.umn.edu 
Strategic Market Games with Production [PDF] We consider several models of a simple economy in which a
single nondurable good is produced and consumed in each of a countable
number of time periods. The agents seek to maximize the expectation of
their total discounted utility derived from consumption of the good. 
Moshe Tennenholtz Technion moshetie.technion.ac.il 
Computation Social Systems: Reputations Systems and NonCoperative Computation The Internet exhibits forms of interactions which are not captured by existing models in economics, computer science, artificial intelligence and game theory. New models are needed in order to deal with these multiagent interactions. In this talk we discuss two such models: reputation systems and noncooperative computation. In reputation systems we are given a reputation graph, where the nodes are agents and the edges correspond to feedback by the agents on the importance/reliability of other agents. The objective is to rank the agents based on this information, in order to cature their importance or reaibility. An example is Google's page rank, where pages are ranked based on the Internet link structure. In the talk we will briefly present an axiomatic approach to the above problem. In noncooperative computation the objective is to compute a function based on private information held by the agents (e.g. each agent may have a private bit of information: 0 or 1, and the objective is to compute the majority function). However, although agents may wish to compute the result of the function, they may have a secondary objective of misleading others, and (if access to infromation is costly) might freeride on other agents' computations. In the talk we briefly discuss few results about which (and how) functions can be correctly computed taking such incentives into account. Together, the talk will expose the audience to several challenges for the theories of social choice and mechanism design, bridging some of the gap between computer science and game theory. The part of presentation dealing with noncooperative computation is based on joint work with Yoav Shoham and Rann Smorodinsky 
Nicolas Vieille Université Montesquieu Bordeaux IV vieillepoly.polytechnique.fr 
Timing games with informational externalities [PDF]  joint work with Dinah Rosenberg (Paris 13) and Eilon Solan (Tel Aviv University and Northwestern University) We analyze the following game of timing with incomplete
information. At each stage n in N, each (of finitely many) player i has
to choose whether to stay in or to drop out from the game. If she stays
in, she receives a random payoff X_i^n. Once out, she receives 0
forever. The various payoffs X_i^n are conditionally independent given
a state of nature £, selected at stage 0 according to some prior
distribution. 
Myrna Wooders University of Warwick M.Wooderswarwick.ac.uk 
Behavioural Conformity and Purification in Games with Many Players [PDF]  joint work with Edward Cartwright and Reinhard Selden This presentation, based on joint research with Edward Cartwright and, in part, with Reinhard Selten, addresses the question of whether behavioural conformity can be consistent with (approximate) Nash equilibrium in pure strategies in strategic games with many players. A major focus of the presentation will be purification results for incomplete information games with countable action sets and countable (Harsanyi) types and a new mathematical result underlying the game theoretic results. Finally, expost Nash equilibria are related to approximate Bayesian equilibria. 
Muhamet Yildiz MIT myildizmit.edu 
Finiteorder implications of any equilibrium [PDF]  joint work with Jonathan Weinstein Present economic theories make a commonknowledge assumption that implies that the first or the secondorder beliefs determine all higherorder beliefs. We analyze the role of such closing assumptions at finite orders by instead allowing higher orders to vary arbitrarily. Assuming that the space of underlying uncertainty is sufficiently rich, we show that the resulting set of possible outcomes, under an arbitrary fixed equilibrium, must include all outcomes that survive iterated elimination of strategies that are never a strict best reply. For many games, this implies that, unless the game is dominancesolvable, every equilibrium will be highly sensitive to higherorder beliefs, and thus economic theories based on such equilibria may be misleading. Moreover, every equilibrium is discontinuous at each type for which two or more actions survive our elimination process. 