Monte Carlo Studies of “Random” Systems

Recent years have seen enormous activity on “random” systems: on the theoretical side, where models containing random parameters in the Hamiltonian are considered (for a magnetic system, one commonly considers randomness in the exchange interaction, in the anisotropy, in the field coupling to the order parameter, etc.); on the experimental side, systems with structural disorder (amorphous systems) as well as various sorts of randomly mixed crystals have been produced and extensively studied. A large number of new phenomena have been identified, some of which are quite different from the more “ideal” systems without such disorder, and many basic questions are still open. At the same time the theoretical methods for describing such systems are much less simple and well developed than for ideal systems, e.g., for systems such as spin glasses, even the proper formulation of a mean-field theory for infinite-range interactions has been a formidable problem, which still lacks a complete solution.