Stability of Ferromagnetism in Many-Electron Systems

摘要

A new viewpoint of universality is introduced in strongly correlated electronsystems; Our description relies on the operator theoretic correlationinequalities. We explain the Marshall-Lieb-Mattis theorem and Liebq{}stheorem from a viewpoint of universality; in addition, from the newperspective, we prove that Liebq{}s theorem still holds true even if theelectron-phonon and electron-photon interactions are taken into account. Wealso study Nagaoka-Thoulessq{} theorem and its stabilities in terms ofuniversality.