Publication: Ground States and Defect Energies of the Two-dimensional XY Spin Glass from a Quasi-Exact Algorithm

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Title	Ground States and Defect Energies of the Two-dimensional XY Spin Glass from a Quasi-Exact Algorithm
Authors/Editors*	M Weigel, M Gingras
Where published*	Physical Review Letters
How published*	Journal
Year*	2006
Volume	96
Number
Pages	097206
Publisher	American Physical Society
Keywords	spin glass; planar model; ground states; domain walls
Link	http://link.aps.org/doi/10.1103/PhysRevLett.96.097206
Abstract	We employ a novel algorithm using a quasiexact embedded-cluster matching technique as minimization method within a genetic algorithm to reliably obtain numerically exact ground states of the Edwards-Anderson XY spin-glass model with bimodal coupling distribution for square lattices of up to 28Ã28 spins. Contrary to previous conjectures, the ground state of each disorder replica is nondegenerate up to a global O(2) rotation. The scaling of spin and chiral defect energies induced by applying several different sets of boundary conditions exhibits strong crossover effects. This suggests that previous calculations have yielded results far from the asymptotic regime. The novel algorithm and the aspect-ratio scaling technique consistently give thetas=-0.308(30) and thetac=-0.114(16) for the spin and chiral stiffness exponents, respectively.