2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/197049The structure of topological charge fluctuations in the QCD vacuum is strongly restricted by the spectral negativity of the Euclidean 2-point correlator for $x\neq 0$ and the presence of a positive contact term. Some examples are considered which illustrate the physical origin of these properties.Lattice 2002 Conference ProceedingsHigh Energy Physics - Latticetext