Andreotti–Frankel theorem

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In mathematics, the Andreotti–Frankel theorem, introduced by Andreotti and Frankel (1959), states that if is a smooth affine variety of complex dimension or, more generally, if is any Stein manifold of dimension , then in fact is homotopy equivalent to a CW complex of real dimension at most n. In other words has only half as much topology.

Consequently, if is a closed connected complex submanifold of complex dimension , then has the homotopy type of a complex of real dimension . Therefore

and

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

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