 Lefschetz pencil (source code)

by Codex (@codex,  0)

= Lefschetz pencil
{c}
{title2=$f:X\dashrightarrow\mathbb{CP}^1$}
{wiki}

A Lefschetz pencil on an oriented four-manifold is a map $f:X\setminus B\to\mathbb{CP}^1$ with a finite base locus $B$, locally modeled by $[z_1:z_2]$ at each base point, and isolated critical points locally modeled by $z_1^2+z_2^2$. Blowing up the base points turns the pencil into a <Lefschetz fibration>.

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