BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Viacheslav Nikulin (Steklov Mathematical Institute\, Russia\; Univ ersity of Liverpool\, UK) DTSTART:20201022T080000Z DTEND:20201022T090000Z DTSTAMP:20260422T212902Z UID:Nilkulin70/1 DESCRIPTION:Title: Classification of degenerations and Picard lattices of Kahlerian K3 sur faces with finite symplectic automorphism group\nby Viacheslav Nikulin (Steklov Mathematical Institute\, Russia\; University of Liverpool\, UK) as part of “Algebraic geometry and arithmetic” Viacheslav Nikulin’s 70th birthday conference\n\n\nAbstract\nI will speak about my results whic h I obtained during last years 2013-2020. This classification is almost fi nished now. Only for very small symplectic automorphism groups of order 4\ , 3\, 2 and 1 it is not completely finished now.\n LOCATION:https://researchseminars.org/talk/Nilkulin70/1/ END:VEVENT BEGIN:VEVENT SUMMARY:JongHae Keum (KIAS\, Korea) DTSTART:20201022T091500Z DTEND:20201022T101500Z DTSTAMP:20260422T212902Z UID:Nilkulin70/2 DESCRIPTION:Title: Automorphism groups of cubic surfaces in arbitrary characteristic\n by JongHae Keum (KIAS\, Korea) as part of “Algebraic geometry and arithm etic” Viacheslav Nikulin’s 70th birthday conference\n\nAbstract: TBA\n LOCATION:https://researchseminars.org/talk/Nilkulin70/2/ END:VEVENT BEGIN:VEVENT SUMMARY:Valery Gritsenko (Université de Lille\, France\; NRU HSE\, Russia ) DTSTART:20201022T121500Z DTEND:20201022T131500Z DTSTAMP:20260422T212902Z UID:Nilkulin70/3 DESCRIPTION:Title: Reflective modular forms\, Lorentzian Kac-Moody algebras and algebraic geometry\nby Valery Gritsenko (Université de Lille\, France\; NRU HSE \, Russia) as part of “Algebraic geometry and arithmetic” Viacheslav N ikulin’s 70th birthday conference\n\n\nAbstract\nIn my talk\, I will rev iew our recent joint results with Viacheslav Nikulin on Lorentzian Kac-Moo dy algebras\, reflexive automorphic forms and their applications to algebr aic geometry.\n LOCATION:https://researchseminars.org/talk/Nilkulin70/3/ END:VEVENT BEGIN:VEVENT SUMMARY:Yuri Prokhorov (Steklov Mathematical Institute\, NRU HSE\, Lomonos ov Moscow State University\, Russia)) DTSTART:20201023T080000Z DTEND:20201023T090000Z DTSTAMP:20260422T212902Z UID:Nilkulin70/4 DESCRIPTION:Title: On the rationality of Fano threefolds over non-closed fields\nby Yu ri Prokhorov (Steklov Mathematical Institute\, NRU HSE\, Lomonosov Moscow State University\, Russia)) as part of “Algebraic geometry and arithmeti c” Viacheslav Nikulin’s 70th birthday conference\n\n\nAbstract\nWe dis cuss rationality problem of smooth Fano threefolds of Picard number one ov er algebraically non-closed fields. The talk is based on a joint work with A. Kuznetsov.\n LOCATION:https://researchseminars.org/talk/Nilkulin70/4/ END:VEVENT BEGIN:VEVENT SUMMARY:Shigeyuki Kondo (Nagoya University\, Japan) DTSTART:20201023T091500Z DTEND:20201023T101500Z DTSTAMP:20260422T212902Z UID:Nilkulin70/5 DESCRIPTION:Title: Enriques surfaces and Leech lattice\nby Shigeyuki Kondo (Nagoya Uni versity\, Japan) as part of “Algebraic geometry and arithmetic” Viache slav Nikulin’s 70th birthday conference\n\n\nAbstract\nLet $L$ be an eve n unimodular lattice of signature $(1\,25)$ which is unique up to isomorph isms. J.H. Conway found a fundamental domain $C$ of the reflection group o f $L$ by using a theory of Leech lattice. Recently S. Brandhorst and I. Sh imada have classified all primitive embeddings of $E_{10}(2)$ into $L$\, w here $E_{10}(2)$ is the pullback of the Picard lattice of an Enriques surf ace to the covering K3 surface. There are exactly $17$ embeddings. By rest ricting $C$ to the positive cone of $E_{10}\\otimes {\\bf R}$ we obtain $1 7$ polyhedrons. In this talk I would like to discuss the automorphism grou ps of Enriques and Coble surfaces in terms of these polyhedrons.\n LOCATION:https://researchseminars.org/talk/Nilkulin70/5/ END:VEVENT BEGIN:VEVENT SUMMARY:Alessandra Sarti (Université de Poitiers\, France) DTSTART:20201023T121500Z DTEND:20201023T131500Z DTSTAMP:20260422T212902Z UID:Nilkulin70/6 DESCRIPTION:Title: K3 surfaces with maximal finite automorphism groups\nby Alessandra Sarti (Université de Poitiers\, France) as part of “Algebraic geometry and arithmetic” Viacheslav Nikulin’s 70th birthday conference\n\n\nAbs tract\nIn the 80's Nikulin classified all the finite abelian groups acting symplectically on a K3 surface and his results inspired an intensive stud y of automorphism groups of K3 surfaces. It was shown by Mukai that the ma ximum order of a finite group acting symplectically on a K3 surface is 960 and that the group is isomorphic to the Mathieu group $M_{20}$. Then Kond o showed that the maximum order of a finite group acting on a K3 surface i s 3840 and this group contains the Mathieu group with index four. Kondo sh owed also that there is a unique K3 surface on which this group acts\, whi ch is a Kummer surface. I will present recent results on finite groups act ing on K3 surfaces\, that contain strictly the Mathieu group and I will cl assify them. I will show that there are exactly three groups and three K3 surfaces with this property. This is a joint work with C. Bonnafé.\n LOCATION:https://researchseminars.org/talk/Nilkulin70/6/ END:VEVENT BEGIN:VEVENT SUMMARY:Valery Alexeev (University of Georgia\, USA) DTSTART:20201023T133000Z DTEND:20201023T143000Z DTSTAMP:20260422T212902Z UID:Nilkulin70/7 DESCRIPTION:Title: Degenerations of elliptic K3 surfaces\nby Valery Alexeev (Universit y of Georgia\, USA) as part of “Algebraic geometry and arithmetic” Via cheslav Nikulin’s 70th birthday conference\n\n\nAbstract\nI will describ e degenerations of elliptic K3 surfaces\, both via Weierstrass models and Kulikov models that lead to a geometrically meaningful toroidal compactifi cation of their moduli. Based on joint work with Engel and Brunyate.\n LOCATION:https://researchseminars.org/talk/Nilkulin70/7/ END:VEVENT END:VCALENDAR