Surface Laplacian
= Surface Laplacian
{title2=$\Delta_s$}
The surface Laplacian is the <Laplace-Beltrami operator> of a surface with its induced <Riemannian metric>. It is $\Delta_sf=\nabla_s\cdot\nabla_sf$, using the <surface gradient> and <surface divergence>. On a sphere of radius $a$, a degree-$l$ <spherical harmonic> has <eigenvalue> $-l(l+1)/a^2$.