| Speaker: |
Takehiko Yasuda (Osaka University) |
| Title: |
Stringy invariants for singularities in positive and mixed characteristics |
| Date (JST): |
Thu, Jul 31, 2025, 15:30 - 17:00 |
| Place: |
Seminar Room A |
| Abstract: |
Stringy invariants have been used to get a few results on singularities that appear in the minimal model program, such as klt singularities, in positive and mixed characteristic settings. These invariants are particularly effective in studying such singularities in low characteristic cases, where many other techniques face obstacles. Recent results utilizing stringy invariants include the following. (1) Criteria for determining when quotients by cyclic groups of order $p^n$ give rise to klt singularities. (2) Quotient singularities arising from permutation representations are canonical. (3) The finiteness of the local étale fundamental group for 2-dimensional klt singularities. In this talk, I will provide an overview of the proofs of these results and discuss a few related open problems.
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