title: Quantum phase transitions and the extended coupled cluster method.
abstract: We discuss the application of an extended version of the coupled cluster method to systems exhibiting a quantum phase transition. We use the lattice O(4) nonlinear sigma model in (1+1) and (3+1) dimensions as an example. We show how simple predictions get modified, leading to the absence of a phase transition in (1+1) dimensions, and strong indications for a phase transition in (3+1) dimensions.
authors: Department of Physics, University of Manchester Institute of Science, P.O. Box 88, Manchester, M60 1QD, United Kingdom. ligterin@ect.it
authors: N E
authors: NE
authors: Ligterink
authors: N R
authors: NR
authors: Walet
authors: R F
authors: RF
authors: Bishop