Riemannian product (source code)

= Riemannian product

For Riemannian manifolds $(M,g)$ and $(N,h)$, the product metric on $M\times N$ is $g\oplus h$. Its Levi-Civita connection and curvature split by factors, so its Ricci and scalar curvatures are the corresponding sums.

This equips a <product manifold> with the direct-sum <Riemannian metric>.