PU/IAS NUMBER THEORY | |

Topic: | Intersection Complex on the Baily-Borel Compactification of Siegel Modular Variety |

Speaker: | Sophie Morel |

Affiliation: | Université Paris 11, France and Member, School of Mathematics |

Date: | Thursday, November 16 |

Time/Room: | 4:30pm - 5:30pm/Princeton University, Fine Hall 214 |

In this talk, I will explain how to compute the trace of a power of the Frobenius endomorphism on the intersection cohomology of the Baily-Borel compactification of a Siegel modular variety. The main tools are : - Kottwitz's calculation of the number of points of PEL Shimura varieties over finite fields; - a theorem of Pink about the direct image in the Baily-Borel compactification of a local system on a Shimura variety; - a new construction of the intermediate extension of a pure perverse sheaf as a weight truncation of the full direct image.