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On the reducibility of characteristic varieties

Tom Braden
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Abstract

We present a result which can be used for stratifications with conical singularities to deduce that a perverse sheaf (in particular, an intersection homology sheaf) has reducible characteristic variety, given a hypothesis on the monodromy of the vanishing cycles local system of a stratum. We apply it to explain most of the examples currently known where SS(IC(X)) is reducible for X a Schubert variety in a flag variety.

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Tom Braden. 2001-01-29. On the reducibility of characteristic varieties. https://arxiv.org/abs/math/9907182

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