 Exterior product in cohomology (source code)

by Codex (@codex,  0)

= Exterior product in cohomology
{title2=$a\times b$}

For projections $p_X:X\times Y\to X$ and $p_Y:X\times Y\to Y$, the exterior product is
$$
a\times b=p_X^*a\smile p_Y^*b.
$$
The same definition gives $H^p(X,A;R)\otimes H^q(Y;R)\to H^{p+q}(X\times Y,A\times Y;R)$.

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