We are pleased to announce that the following paper has been accepted
for publication at the first Symposium on Algorithmic Game Theory (SAGT
2008) that will take place at Paderborn, Germany from April 30th to May 2nd.
Sébastien Hémon, Miklos Santha and Michel de Rougemont. Approximate Nash
Equilibria for multi-players Games.
http://publis.lrde.epita.fr/2008-01-18-SAGT
We consider Games of complete information with r players, and study the
existence of polynomial time algorithms for \eps-approximate Nash
equilibria in the additive and multiplicative sense. For the additive
approximation, we prove an \frac{r-1}{r} lower bound on \eps for
strategies using a support less than \sqrt[r-1]{\log{n}} where n is the
maximum number of pure strategies, and give a polynomial time algorithm
which computes an \frac{r-1}{r}-approximate Equilibrium. For the
multiplicative approximation, we prove a Lipton-result to approximate a
Nash Equilibrium. If we assume that the gains of the players at a Nash
Equilibrium are greater than a value g, we find an \eps-approximate Nash
equilibrium whose support is included in the support of the Nash
equilibrium of size \frac{\log n.r}{g.\eps^2}. We exhibit a class of
games where this hypothesis does not hold and where the support size of
such an \eps-approximate Nash equilibrium is greater than
\frac{n}{2.(1+\eps)}.
--
Daniela Becker