2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/66200Suppose that Fourier transform of a function f is zero on the interval [-a,a]. We prove that the lower density of sign changes of f is at least a/pi, provided that f is a locally integrable temperate distribution in the sense of Beurling, with non-quasianalytic weight. We construct an example showing that the last condition cannot be omitted.1 FigureClassical Analysis and ODEsComplex Variables42A38 46F12 46F20text