On the Hardness and Existence of Quasi-Strict Equilibria

  • Felix Brandt
  • Felix Fischer
Part of the Lecture Notes in Computer Science book series (LNCS, volume 4997)


This paper investigates the computational properties of quasi-strict equilibrium, an attractive equilibrium refinement proposed by Harsanyi, which was recently shown to always exist in bimatrix games. We prove that deciding the existence of a quasi-strict equilibrium in games with more than two players is NP-complete. We further show that, in contrast to Nash equilibrium, the support of quasi-strict equilibrium in zero-sum games is unique and propose a linear program to compute quasi-strict equilibria in these games. Finally, we prove that every symmetric multi-player game where each player has two actions at his disposal contains an efficiently computable quasi-strict equilibrium which may itself be asymmetric.


Nash Equilibrium Positive Probability Pure Nash Equilibrium Graphical Game Symmetric Game 
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© Springer-Verlag Berlin Heidelberg 2008

Authors and Affiliations

  • Felix Brandt
    • 1
  • Felix Fischer
    • 1
  1. 1.Institut für InformatikUniversität MünchenMünchenGermany

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