Harmonic differential form
= Harmonic differential form
{title2=$\Delta\alpha=0$}
= Harmonic form
{synonym}
A differential form is harmonic when it lies in the kernel of the Hodge Laplacian $\Delta=d\delta+\delta d$. On a compact manifold, this is equivalent to $d\alpha=0$ and $\delta\alpha=0$.
Its relation to cohomology is part of <Hodge theory>.