Sonali Sen Gupta

Improving Nash by coarse correlation

We consider a class of symmetric two-person quadratic games where coarse correlated equilibria – CCE – (Moulin and Vial [16]) can strictly improve upon the Nash equilibrium payoffs, while correlated equilibrium – CE – (Aumann [3,4]) cannot, because these games are potential games with concave potential functions. We compute the largest feasible total utility in any CCE in those games and show that it is achieved by a CCE involving only two pure strategy profiles. Applications include the Cournot duopoly and the game of public good provision, where the improvement over and above the Nash equilibrium payoff can be substantial.

Coarse correlated equilibria in linear duopoly games

For duopoly models, we analyse the concept of coarse correlated equilibrium using simple symmetric devices that the players choose to commit to in equilibrium. In a linear duopoly game, we prove that Nash-centric devices, involving a sunspot structure, are simple symmetric coarse correlated equilibria. Any small unilateral perturbation from such a structure fails to be an equilibrium.

Pricing toll roads under uncertainty

We study the toll pricing problem when the non-toll costs on the network are not fixed and can vary over time. We assume that users who take their decisions, after the tolls are fixed, have full information of all costs before making their decision. Toll-setter, on the other hand, do not have any information of the future costs on the network. The only information toll-setter have is historical information (sample) of the network costs. In this work we study this problem on parallel networks and networks with few number of paths in single origin-destination setting. We formulate toll-setting problem in this setting as a distributionally robust optimization problem and propose a method to solve to it. We illustrate the usefulness of our approach by doing numerical experiments using a parallel network.