Let $M$ be a manifold with the differential $d$ acting on exterior forms. A differential operator $\delta$ is defined by:
$$\delta (\alpha)= d \alpha \wedge \beta$$
with $\beta \wedge d \beta=0$, then we have $\delta \circ \delta =0$. The cohomology is defined:
$$ H^*_{\beta}(M,{\bf R})=Ker(\delta)/Im(\delta)$$
Can we find new topological invariants of manifolds?