Temperature Chaos and Bond Chaos in the Four-Dimensional
±J Ising Spin Glass : Domain-Wall Free-Energy Measurements
The statistics of domain walls for ground states of the 2D Ising spin glass with +1 and -1 bonds are studied for
L×L square lattices with
L≤20, and
x = 0.25 and 0.5, where
x is the fraction of negative bonds, using periodic and/or antiperiodic boundary conditions. Under these conditions, almost all domain walls have an energy
Edw equal to 0 or 4. The probability distribution of the entropy,
Sdw, is found to depend strongly on
Edw. The results for
Sdw when
Edw=4 agree with the prediction of the droplet model. Our results for
Sdw when
Edw=0 agree with those of Saul and Kardar. In addition, we find that the distributions do not appear to be Gaussian in that case. The special role of
Edw=0 domain walls is discussed, and the discrepancy between the prediction of Amoruso, Hartmann, Hastings and Moore and the result of Saul and Kardar is explained.
We study the scaling behavior of domain-wall energies in two-dimensional Ising spin glasses with Gaussian and bimodal distributions of the interactions and different types of boundary conditions. The domain walls are generated by changing the boundary conditions at
T=0 in one direction. The ground states of the original and perturbed system are calculated numerically by applying an efficient matching algorithm. Systems of size $L\ifmmode\times\else\texttimes\fi{}M$ with different aspect-ratios
1/8< L/M< 64 are considered. For Gaussian interactions, using the aspect-ratio scaling approach, we find a stiffness exponent $\ensuremath{\theta}=\ensuremath{-}0.287(4),$ which is independent of the boundary conditions in contrast to earlier results. Furthermore, we find a scaling behavior of the domain-wall energy as predicted by the aspect-ratio approach. Finally, we show that this approach does not work for the bimodal distribution of interactions.