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Search options not deleted user 919
14 votes
2 answers
935 views

Non semi-simple monodromy in an algebraic family

of a (edit: projective) family $f : X \to Y$ of complex algebraic varieties which is a topologically locally trivial fibration in (singular) varieties and such that there exists an $q$ such that the monodromy … Indeed, if $Y = \mathbb{A}^1 \setminus \{ x_1, \dots, x_n \}$ and $f$ is smooth then the monodromy around any $x_i$ will be quasi-unipotent. …
Geordie Williamson's user avatar
4 votes

Non semi-simple monodromy in an algebraic family

So it seems passerby's example can be modified to give a projective example. (Thanks for de Cataldo and Migliorini for some of the following. All mistakes are mine.) Fix $E$ an elliptic curve and …
Geordie Williamson's user avatar
27 votes
0 answers
953 views

Nearby cycles without a function

Firstly, $\psi_f(\mathbb{Q}_X)$ is a perverse sheaf, and it comes with a monodromy endomorphism $\mu$. I assume that $\mu$ is unipotent. … Secondly, $\psi_f(\mathbb{Q}_X)$ carries a weight filtration $W$, and a deep theorem of Gabber states that the weight filtration agrees with the monodromy filtration. …
Geordie Williamson's user avatar