title: Correlation Inequalities for the Quantum XY Model.
abstract: We show the positivity or negativity of truncated correlation functions in the quantum XY model with spin 1/2 (at any temperature) and spin 1 (in the ground state). These Griffiths-Ginibre inequalities of the second kind generalise an earlier result of Gallavotti.
authors.affiliation: Department of Mathematics, University of Warwick, Coventry, CV4 7AL UK.
authors.forename: Costanza
authors.initials: C
authors.lastname: Benassi
authors.affiliation: Department of Mathematics, University of Warwick, Coventry, CV4 7AL UK.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Lees
authors.affiliation: Department of Mathematics, University of Warwick, Coventry, CV4 7AL UK.
authors.forename: Daniel
authors.identifier: 0000-0003-1192-5378
authors.initials: D
authors.lastname: Ueltschi
keywords: Correlation inequalities; Griffiths inequalities; Quantum XY model