Spring 2026
Seminar time and location:
Thursday 15:15-16:15, Jingchunyuan 77201
Information can also be found on Professor Qizheng Yin's webpage or the official webpage.
March 12th
Speaker: 范智庥 (Zhixiu Fan) (Fudan University)
Title: Volumes of foliations birationally bounded by algebraically integrable families
Abstract: In this talk, I will present a recent result regarding the volumes of foliations. We prove that for log canonical foliations which are birationally bounded by algebraically integrable families, the set of their volumes satisfies the DCC, answering a special case of a question posed by Cascini, Hacon, and Langer. As a key ingredient, I will discuss the deformation invariance of relative log canonical volumes for a family of weakly semistable morphisms, which can be viewed as a relative version of the result proved by Hacon, McKernan, and Xu.
March 19th
Speaker: 龚挺 (Ting Gong) (University of Washington)
Title: Moduli of twisted vector bundles and the period index problem
Abstract: The period index problem has been suggested by Colliot-Thélène in early 2000s, and some of its low dimensional cases has been solved by de Jong, Lieblich and more recently Perry-Hotchkiss. We adapt the point of view of moduli of twisted sheaves, and by combining classical results in the theory of moduli of vector bundles, we realize the moduli of twisted vector bundles as the obstruction class of descending the determinantal line bundle; thus giving a bound on the period index problem for genus 2 curves over an arbitrary field.
March 26th
Speaker: Salvatore Floccari (Humboldt-Universität zu Berlin)
Title: Weil fourfolds with discriminant 1 and singular OG6-varieties
Abstract: Markman and O'Grady uncovered a deep relation between abelian fourfolds of Weil type with discriminant 1 and hyper-Kähler varieties of generalized Kummer type, at the level of Hodge theory and period domains. Markman was able to use this to prove the Hodge conjecture for these fourfolds; he later found also a different proof which works for Weil fourfolds with arbitrary discriminant. In my talk I will explain how Weil fourfolds with discriminant 1 are very closely related to certain hyper-Kähler varieties of OG6-type, in a direct and geometric way. As a consequence, we obtain another proof of the Hodge conjecture for Weil fourfolds with discriminant 1, as well as for many families of hyper-Kähler varieties of OG6-type which form loci of codimension 1 in their moduli spaces. The results that I will discuss are joint work with Lie Fu.
April 2nd
Speaker: André Belotto da Silva (Université Paris Cité, Institut de Mathématiques de Jussieu-Paris Rive Gauche)
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April 9th
Speaker: Lena Ji (University of Illinois at Urbana-Champaign)
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April 16th
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April 23rd
Speaker: Jefferson Baudin (École Polytechnique Fédérale de Lausanne)
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April 30th
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May 7th
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May 14th
Cancelled due to the Beijing-Hangzhou-Zurich Moduli Workshop
May 21st
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May 28th
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June 4th
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June 11th
Speaker: 松澤陽介 (Yohsuke Matsuzawa) (Osaka Metropolitan University)
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