In mathematics — specifically, differential geometry — the Bochner identity is an identity concerning harmonic maps between Riemannian manifolds. The identity is named after the American mathematician Salomon Bochner.
Let M and N be Riemannian manifolds and let u : M â N be a harmonic map. Let du denote the derivative (pushforward) of u, â the gradient, àthe LaplaceâÂÂBeltrami operator, Riem<sub>N</sub> the Riemann curvature tensor on N and Ric<sub>M</sub> the Ricci curvature tensor on M. Then