2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/49605After recalling some connections between the Spontaneous Breakdown of Chiral Symmetry (SBChS) and the spectrum of the Dirac operator for Euclidean QCD on a torus, we use this tool to reconsider two related issues : the Zweig rule violation in the scalar channel and the dependence of SBChS order parameters on the number N_f of massless flavours. The latter would result into a great variety of SBChS patterns in the (N_f,N_c) plane, which could be studied through so-called Leutwyler-Smilga sum rules in association with lattice computations of the Dirac spectrum.6 pages, no figure, class file included. Talk given at the XVII International School of Physics "QCD: Perturbative or Nonperturbative", Lisbon, Portugal, 29 September - 4 October 1999, to appear in the ProceedingsHigh Energy Physics - PhenomenologyHigh Energy Physics - Latticetext