Local invariant cycle theorem
In mathematics, the local invariant cycle theorem was originally a conjecture of Griffiths which states that, given a surjective proper map p {\displaystyle p} from a Kähler manifold X {\displaystyle X} to the unit disk that has maximal rank everywhere except over 0, each cohomology class on p − 1 ( t ) , t ≠ 0 {\displaystyle p^{-1}(t),t\neq 0} is the restriction of some cohomology class on the entire X {\displaystyle X} if the cohomology class is invariant under a circle action (monodromy action); in short, H ∗ ( X ) → H ∗ ( p − 1 ( t ) ) S 1 {\displaystyle \operatorname {H} ^{*}(X)\to \operatorname {H} ^{*}(p^{-1}(t))^{S^{1}}} is surjective. The conjecture was first proved by Clemens.
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