Steady state behavior of mechanically perturbed spin glasses and ferromagnets - art. no. 046110

A zero temperature dynamics of Ising spin glasses and ferromagnets on rando m graphs of finite connectivity is considered. Like granular media, these s ystems have an extensive entropy of metastable states. We consider the prob lem of what energy a randomly prepared spin system falls to before becoming stuck in a metastable state. We then introduce a tapping mechanism, analog ous to that found in real experiments on granular media. This tapping, corr esponding to flipping each spin with probability p simultaneously, leads to a stationary regime with a steady state energy E(p). We explicitly solve t his problem for the one-dimensional ferromagnet and the +/-J spin glass, an d carry out extensive numerical simulations for spin systems of higher conn ectivity. In addition our simulations on the ferromagnetic systems reveal a first order transition, whereas the usual thermodynamic transition on thes e graphs is second order.