Topological excitations near the local critical point in the dissipative two-dimensional XY model

The dissipative XY model in two spatial dimensions belongs to a new universality class of quantum-critical phenomena with the remarkable property of the decoupling of the critical fluctuations in space and time. We have shown earlier that the quantum-critical point is driven by proliferation in time of topological configurations that we termed warps. We show here that a warp may be regarded as a configuration of a monopoles surrounded symmetrically by antimonopoles so that the total charge of the configuration is zero. Therefore the interaction with other warps is local in space. They, however, interact with other warps at the same spatial point logarithmically in time. As a function of dissipation warps unbind leading to a quantum phase transition. The critical fluctuations are momentum independent but have power-law correlations in time.