Dynamics and Coalitions in Sequential Games

Thomas Brihaye
Gilles Geeraerts
(Université libre de Bruxelles)
Marion Hallet
Stéphane Le Roux
(Université libre de Bruxelles)

We consider N-player non-zero sum games played on finite trees (i.e., sequential games), in which the players have the right to repeatedly update their respective strategies (for instance, to improve the outcome wrt to the current strategy profile). This generates a dynamics in the game which may eventually stabilise to a Nash Equilibrium (as with Kukushkin's lazy improvement), and we argue that it is interesting to study the conditions that guarantee such a dynamics to terminate.

We build on the works of Le Roux and Pauly who have studied extensively one such dynamics, namely the Lazy Improvement Dynamics. We extend these works by first defining a turn-based dynamics, proving that it terminates on subgame perfect equilibria, and showing that several variants do not terminate. Second, we define a variant of Kukushkin's lazy improvement where the players may now form coalitions to change strategies. We show how properties of the players' preferences on the outcomes affect the termination of this dynamics, and we thereby characterise classes of games where it always terminates (in particular two-player games).

In Patricia Bouyer, Andrea Orlandini and Pierluigi San Pietro: Proceedings Eighth International Symposium on Games, Automata, Logics and Formal Verification (GandALF 2017), Roma, Italy, 20-22 September 2017, Electronic Proceedings in Theoretical Computer Science 256, pp. 136–150.
Published: 6th September 2017.

ArXived at: http://dx.doi.org/10.4204/EPTCS.256.10 bibtex PDF
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