Title: Ramification groups of a local field (with Ahmed Abbes and Kazuya Kato) Speaker: Takeshi Saito (斋藤毅 东京大学) Time: 2019-9-5, 10:00—11:30 Place: N202 Abstract: 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. Attachment: