Lundi 15 juin 2015
IRMA
The "Joint Seminar in Algebraic and Complex Geometry" is a research seminar, organized by the research groups in Basel, Freiburg, Nancy and Strasbourg. The seminar meets roughly twice per semester in Strasbourg, for a full day. There are about four talks per meeting, both by invited guests and by speakers from the organizing universities. We aim to leave ample room for discussions and for a friendly chat.
The talks are open for everyone. Contact one of the organizers if you are interested in attending the meeting. We have some (very limited) funds that might help to support travel for some junior participants.
The seminar will meet in Strasbourg, June 15th in the conference room of the institute.
Organizer : G. Pacienza (Strasbourg)
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Lundi 15 juin 2015
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10:30
Robert Laterveer, Strasbourg
Hard Lefschetz for Chow groups
Inspired by the conjectural Bloch-Beilinson filtration, we formulate a conjectural hard Lefschetz property for the Chow groups of a smooth projective algebraic variety over the complex numbers. This property can be verified in some special cases – roughly speaking, for varieties for which the self-product has vanishing middle-dimensional Griffiths group, and for varieties that have finite-dimensional motive (in the sense of Kimura). As we will explain, closely related (but slightly different) results can also be deduced from recent work of Charles Vial. -
11:45
Susanna Zimmermann, Basel
An Abelian quotient of the real Cremona group
The Cremona group of the complex plane contains many normal subgroups, all of which are of infinite index. There is no proper normal subgroup containing elements of degree 1 (not equal to the identity map), 2, 3 and 4. What about the Cremona group of the real plane? I will present an abelian quotient of it, which implies the existence of normal subgroups of index equal to any given power of 2, all of them containing every map of degree 1, 2, 3, and 4. -
14:30
Giulia Battiston, Freiburg
A Galois descent theory for inseparable field extension
The Cremona group of the complex plane contains many normal subgroups, all of which are of infinite index. There is no proper normal subgroup containing elements of degree 1 (not equal to the identity map), 2, 3 and 4. What about the Cremona group of the real plane? I will present an abelian quotient of it, which implies the existence of normal subgroups of index equal to any given power of 2, all of them containing every map of degree 1, 2, 3, and 4. -
16:00
Zsolt Patakfalvi, Princeton
Projectivity of the moduli space of KSBA stable pairs and applications
KSBA (Kollár-Shepherd-Barron-Alexeev) stable pairs are higher dimensional generalizations of (weighted) stable pointed curves. I will present a joint work in progress with Sándor Kovács on proving the projectivity of this moduli space, by showing that certain Hodge-type line bundles are ample on it. I will also mention applications to the subadditivity of logarithmic Kodaira dimension, and to the ampleness of the CM (Chow-Mumford) line bundle.