时间：2019年9月4日（周三）9:45—10:45
地点：南楼202
报告人：Takeshi Saito (斋藤毅 东京大学)
题目：Characteristic cycle of an l-adic sheaf
摘要：
For an l-adic sheaf on a smooth variety over a perfect field of characteristic p >= 0, its characteristic cycle is defined as a cycle supported on the singular support, defined by Beilinson as a conical closed subset of the cotangent bundle of the variety. This is an algebraic analogue of that constructed by Kashiwara-Schapira in a transcendental setting.

时间：2019年9月5日（周四）10:00—11:30
地点：南楼202
报告人：Takeshi Saito (斋藤毅 东京大学)
题目：Ramification groups of a local field (with Ahmed Abbes and Kazuya Kato)
摘要：
For a Galois extension of a discrete valuation field with not necessarily perfect residue field, two filtrations (logarithmic and non-logarithmic) by ramification groups are defined by a geometric method by Abbes and myself. For an abelian extension, another filtration is defined earlier by Kato by a cohomological method. After briefly recalling the definition, we discuss a recent result with Kato on the equality of Kato's filtration with the logarithmic filtration.