The random field Ising model

S. I. Kubarev

Nikolaos G. Fytas, Víctor Martín-Mayor, Marco Picco +1 more

The random-field Ising model is one of the few disordered systems where the perturbative renormalization group can be carried out to all orders of perturbation theory. This analysis predicts dimensional reduction, i.e., that the critical properties of the random-field Ising model in D dimensions are identical to those of the pure Ising ferromagnet in D-2 dimensions. It is well known that dimensional reduction is not true in three dimensions, thus invalidating the perturbative renormalization group prediction. Here, we report high-precision numerical simulations of the 5D random-field Ising model at zero temperature. We illustrate universality by comparing different probability distributions for the random fields. We compute all the relevant critical exponents (including the critical slowing down exponent for the ground-state finding algorithm), as well as several other renormalization-group invariants. The estimated values of the critical exponents of the 5D random-field Ising model are statistically compatible to those of the pure 3D Ising ferromagnet. These results support the restoration of dimensional reduction at D=5. We thus conclude that the failure of the perturbative renormalization group is a low-dimensional phenomenon. We close our contribution by comparing universal quantities for the random-field problem at dimensions 3≤D<6 to their values in the pure Ising model at D-2 dimensions, and we provide a clear verification of the Rushbrooke equality at all studied dimensions.

Subir Sachdev A

Fangxuan Liu, L.-M. Duan

The Ising model is a widely studied class of models in quantum computation. In this paper, we investigate the computational characteristics of the random-field Ising model (RFIM) with long-range interactions that decays as an inverse polynomial of distance, which can be achieved in the current ion trap system. We prove that for an RFIM with long-range interaction embedded on a two-dimensional plane, solving its ground state is NP-complete for all diminishing exponents, and prove that the one-dimensional RFIM with long-range interaction can be efficiently approximated when the interaction decays fast enough.

Terufumi Yokota

Fluctuations can break down mean-field critical behaviour. For the random-field Ising model, fluctuations caused by the randomness are important. The Ginzburg criteria based on two kinds of mean-field theory are discussed. One is the mean-field theory using the replica method and the other is the site-dependent mean-field theory. An argument that justifies the use of the site-dependent mean-field theory to obtain critical properties for the random-field Ising model is given.

George Allen Baker Jr.