Regensburg 2004 – scientific programme

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DY: Dynamik und Statistische Physik

DY 26: General Statistical Physics

DY 26.2: Talk

Tuesday, March 9, 2004, 17:00–17:15, H2

Domain-Wall Energy Analysis of exact Ground States for ± J SG model in D=2 — •Amoruso Carlo and Alexander K.Hartmann — Institute for Theoretical Physics, Göttingen

Computing ground states of Spin Glasses is a NP-hard problem, this means that only algorithms are known, where the running time in the worst case increases exponentially with the system size. For the special case of two-dimensional spin glasses without an external field and with periodic boundary conditions in at most one direction, efficient polynomial algorithms for the calculation of exact ground states are available. By using a matching algorithm, we computed exact ground states of two dimensional Ising Spin Glasses with a certain concentration of antiferromagnetic bonds p up to size L=700. We calculated with high precision the critical concentration of p_c at which the ferromagnetic phase ceases to exist, obtaining p_c = 0.103(1). If the Nishimori point p_N is located on the phase boundary (as believed), the phase diagram has a small reentrance, since p_N ∼ 0.110. Besides we show that there is no spin-glass phase at finite temperature.