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Center for Nonlinear Studies |
The Edwards-Anderson Ising spin glass in two dimensions possesses the disorder and frustration necessary to describe the rich behavior found in glassy materials with complex free-energy landscapes. It also finds application in other areas, such as the computation of error thresholds in models of topological quantum computers. Glassy models are typically NP-hard, so that their solutions are thought to require time exponential in the size of the problem, but the two-dimensional spin glass is a fortunate special case which permits efficient exact simulation. We use recently-developed algorithms to calculate partition functions and to sample configurations exactly from the Boltzmann distribution up to L=512 down to low temperatures. We find that the length scale at which entropy becomes important and produces "chaos", the extreme sensitivity of the state to temperature, is found to depend on the type of randomness. Although there is a type of universality, some critical exponents depend on the distribution of disorder, including the specific heat exponent.
Host: Misha Chertkov, chertkov@lanl.gov, 665-8119