title: Dipolar spin correlations in classical pyrochlore magnets.
abstract: We study spin correlations for the highly frustrated classical pyrochlore lattice antiferromagnets with O(N) symmetry in the limit T-->0. We conjecture that a local constraint obeyed by the extensively degenerate ground states dictates a dipolar form for the asymptotic spin correlations, at all N not equal 2 for which the system is paramagnetic down to T=0. We verify this conjecture in the cases N=1 and N=3 by simulations and to all orders in the 1/N expansion about the solvable N=infinity limit. Remarkably, the N=infinity formulas are an excellent fit, at all distances, to the correlators at N=3 and even at N=1. Thus we obtain a simple analytical expression also for the correlations of the equivalent models of spin ice and cubic water ice, Ic.
authors.affiliation: Department of Physics, AlbaNova, Stockholm University, SE-10691 Stockholm, Sweden.
authors.forename: S V
authors.initials: SV
authors.lastname: Isakov
authors.forename: K
authors.initials: K
authors.lastname: Gregor
authors.forename: R
authors.initials: R
authors.lastname: Moessner
authors.forename: S L
authors.initials: SL
authors.lastname: Sondhi