Chiral symmetry and spectrum of Euclidean Dirac operator

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After 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 Nf of massless flavours. The latter would result into a great variety of SBChS patterns in the (Nf,Nc) plane, which could be studied through so-called Leutwyler-Smilga sum rules in association with lattice computations of the Dirac spectrum.