Tri-critical behavior of the Blume–Emery–Griffiths model on a Kagomé lattice: Effective-field theory and Rigorous bounds

Abstract

Spin correlation identities for the Blume–Emery–Griffiths model on Kagomé lattice are derived and combined with rigorous correlation inequalities lead to upper bounds on the critical temperature. From the spin correlation identities the mean field approximation and the effective field approximation results for the magnetization, the critical frontiers and the tricritical points are obtained. The rigorous upper bounds on the critical temperature improve over those effective-field type theories results.