Andreotti–Frankel theorem

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In mathematics, the Andreotti–Frankel theorem states that if V is a smooth affine variety of complex dimension n or, more generally, if V is any Stein manifold of dimension n, then in fact V is homotopy equivalent to a CW complex of real dimension at most n. In other words V has only half as much topology.

Consequently, if V \subseteq C^r is a closed connected complex submanifold of complex dimension n. Then V has the homotopy type of a CW complex of real dimension \le n. Therefore

H^i(V; \bold Z)=0, for i > n

and

H_i(V; \bold Z)=0, for i > n.

This theorem applies in particular to any smooth affine variety of dimension n.