Martin Pelikan Jiri Ocenasek Simon Trebst Matthias Troyer Fabien Alet Computational complexity and simulation of rare events of Ising spin glasses http://arxiv.org/abs/cs.NE/0402030 2004 CoRR cs.NE/0402030 db/journals/corr/corr0402.html#cs-NE-0402030 informal publication