Universality aspects of the trimodal random-field Ising model

We investigate the critical properties of the d = 3 random-field Ising model with an equal-weight trimodal distribution at zero temperature. By implementing suitable graph-theoretical algorithms, we compute large ensembles of ground states for several values of the disorder strength h and system sizes up to N = 1283. Using a new approach based on the sample-to-sample fluctuations of the order parameter of the system and proper finite-size scaling techniques we estimate the critical disorder strength h c = 2.747(3) and the critical exponents of the correlation length ν = 1.34(6) and order parameter β = 0.016(4). These estimates place the model into the universality class of the corresponding Gaussian random-field Ising model.