2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/59465In the context of synthetic differential geometry, we study the Laplace operator an a Riemannian manifold. The main new aspect is a neighbourhood of the diagonal, smaller than the second neighbourhood usually required as support for second order differential operators. The new neighbourhood has the property that a function is affine on it if and only if it is harmonic.19 pagesCategory TheoryDifferential Geometry18F99;53B20text