Bell's inequalities for states with positive partial transpose - art. no. 062102

We study violations of n-particle Bell inequalities (as developed by Mermin and Klyshko) under the assumption that suitable partial transposes of the density operator are positive. If all transposes with respect to a partitio n of the system into p subsystems are positive, the best upper bound on the violation is 2((n-p)/2). In particular, if the partial transposes with res pect to all subsystems are positive, the inequalities are satisfied. This i s supporting evidence for a recent conjecture by Peres that positivity of p artial transposes could be equivalent to the existence of local classical m odels.