Symmetric‐group algebraic variational solutions for Heisenberg models at finite temperature

Abstract

AbstractThe Heisenberg spin Hamiltonian for a collection of N spin‐1/2 sites is viewed, as favored by Professor Matsen, to be an element of the group algebra of the symmetric group 𝒮N. Several computationally tractable, variational group–algebraic approximations for the finite‐temperature density matrix are made so as to minimize the Gibb's free–energy functional. Relations to previous quite differently motivated approximations are identified, though improvements are noted with the present approach.