2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/56709It is generally believed that the ground state of the ferromagnetic Heisenberg-Dirac-Van Vleck Hamiltonians acting on s=1/2 spins of a lattice with N sites has the maximal possible value of the total spin S=N/2 and is N+1 times degenerate. We present a rigorous proof of this statement, independent of the lattice dimension and topology.7 pagesMathematical Physics81V99text