Cap product
= Cap product
{title2=$\frown$}
{wiki}
The cap product pairs a homology class and a cohomology class to lower degree:
$$
H_p(X;R)\otimes H^k(X;R)\longrightarrow H_{p-k}(X;R).
$$
= Cap product
{title2=$\frown$}
{wiki}
The cap product pairs a homology class and a cohomology class to lower degree:
$$
H_p(X;R)\otimes H^k(X;R)\longrightarrow H_{p-k}(X;R).
$$