Speaker
Description
Several recent experiments in atomic, molecular and optical systems motivated a huge interest in the study of quantum long-range spin systems, following a long-standing interest in classical interacting long-range systems. The goal of the talk is to present a general description of the critical behavior and phases of long-range systems. In the first part I will first discuss and review results on classical long-range systems. By introducing a convenient ansatz for the effective action, one can determine the phase diagram for the N-component quantum rotor model with long-range interactions, with N=1 corresponding to the Ising model. The phase diagram shows a non-trivial dependence on the power-law exponent of the spatial decay of the couplings.