2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/159384In this note we present some gradient estimates for the diffusion equation $\partial_t u=Δu-\nabla ϕ\cdot \nabla u $ on Riemannian manifolds, where $ϕ$ is a C^2 function, which generalize estimates of R. Hamilton's and Qi S. Zhang's on the heat equation.3 pagesDifferential Geometry58J35text