Information Trading in Social Networks (job market paper, 2007)

This paper considers information trading in fixed networks of economic agents who can only observe and trade with other agents with whom they are directly connected. We study the nature of price competition for information in this environment. The linear network, when the agents are located at the integer points of the real line, is a specific example I completely characterize. For the linear network there always exists a stationary equilibrium, where the strategies do not depend on time. I show that there is an equilibrium where any agent has a nonzero probability of staying uninformed forever. Under certain initial conditions this equilibrium is a limit of equilibria of finite-horizon games. The role of a transversality condition is emphasized, namely that the price in the transaction should not exceed the expected utility of all the agents who will get the information due to the transaction. I show that the price offered does not converge to zero with time.

A Theory of Continuum Economies with Idiosyncratic Shocks and Random Meetings

Many economic models use a continuum of agents to avoid considering one agent's effect on others. Along with a continuum of agents, these models also incorporate independent shocks and random meetings over time (Edward J. Green, Ruilin Zhou, 2002. "Dynamic Monetary Equilibrium in a Random Matching Economy". Econometrica, vol. 70). Questions have been raised about the mathematical consistency of the assumptions used. In this paper we demonstrate that it is possible to construct a framework in which the desirable properties, including no aggregate uncertainty and mixing, hold. The main new idea is that the agents live in the probability space, and the probability distribution for each agent is replaced by the population distribution over the states. Although each agent knows his history of shocks and meetings, he does not know his "location" in this space.

Limit Epsilon-Equilibria (With Sophie Bade) (will be available soon)

It has been suggested to use epsilon-equilibrium as a solution concept for the games without Nash equilibria. A strategy profile is called an epsilon-equilibrium if no player can improve his utility by more than epsilon given all other players' strategies. To mitigate the dependence of the arbitrarily picked epsilon, it seems appropriate to focus on strategy profiles that are limits of sequences of epsilon-equilibria with epsilon converging to 0. To calculate such limits of epsilon-equilibria, one needs to first calculate epsilon-equilibria as fixed points of epsilon-best response correspondences for every epsilon in a sequence that converges to 0. Next, one needs to search for all converging subsequences of such sequences of epsilon-equilibria.

In this paper, we investigate the conditions under which this procedure can be inverted. According to the "inverted procedure," one would first calculate the limits of epsilon-best response correspondences, and then calculate the set of fixed points of these limits. This inversion simplifies the analysis; it requires only one calculation of the set of fixed points. We show that, while the "inverted procedure" does not generally yield the set of limit epsilon-equilibria, it can be used to establish an upper bound on the set of all epsilon-equilibria. Then, we determine the sufficient conditions for the result of the "inverted procedure" to coincide with the set of limit epsilon-equilibria.

"Pareto Effectiveness of Equilibria in Active Systems with Distributed Control." (translated from Russian) Automation and Remote Control, 63 (12), 2002, pp. 1880-1895

"Coordination of Interests in the Matrix Control Structures" (with M. Gubko). (translated from Russian) Automation and Remote Control, 62 (10), 2001, pp. 1658-1672

"Uniform Stimulation Systems." (translated from Russian) Automation and Remote Control, 64 (1), 2003, pp. 104-137