Seminars

2018 May 10

Groups & dynamics: Sanghoon Kwon (Kwandong University) - A combinatorial approach to the Littlewood conjecture in positive characteristic

10:30am to 11:30am

Location: 

Ross 70
The Littlewood conjecture is an open problem in simultaneous Diophantine approximation of two real numbers. Similar problem in a field K of formal series over finite fields is also still open. This positive characteristic version of problem is equivalent to whether there is a certain bounded orbit of diagonal semigroup action on Bruhat-Tits building of PGL(3,K).
2017 Nov 28

T&G: Benjamin Ackermann (Hebrew University), Kodaira's embedding theorem

12:00pm to 1:30pm

Location: 

Room 70A, Ross Building, Jerusalem, Israel
In this talk we present a proof of the Kodaira's theorem that gives a sufficient condition on the existence of an embedding of a Kahler manifold into CPn. This proof is based on the Kodaira Vanishing theorem, using a sheaf-cohomological translation of the embedding conditions. לאירוע הזה יש שיחת וידאו. הצטרף: https://meet.google.com/mcs-bwxr-iza
2015 Nov 09

Number theory: Ishai Dan-Cohen (Essen), "Towards Chabauty-Kim loci for the polylogarithmic quotient over an arbitrary number field"

4:00pm to 5:45pm

Location: 

Ross Building, room 70, Jerusalem, Israel
Title: Towards Chabauty-Kim loci for the polylogarithmic quotient over an arbitrary number field Abstract: Let K be a number field and let S be an open subscheme of Spec O_K. Minhyong Kim has developed a method for bounding the set of S-valued points on a hyperbolic curve X over S; his method opens a new avenue in the quest for an "effective Mordell conjecture". But although Kim's approach has lead to the construction of explicit bounds in special cases, the problem of realizing the potential effectivity of his methods remains a difficult and beautiful open problem.
2015 Dec 07

Number theory: Jean-Baptiste Teyssier (HUJI) "Kedlaya-Mochizuki theorem and applications"

4:00pm to 5:15pm

Location: 

Ross Building, room 70A
Let X be a complex manifold and let M be a meromorphic connection on X with poles along a normal crossing divisor D. Levelt-Turrittin theorem asserts that the pull-back of M to the formal neighbourhood of a codimension 1 point in D decom poses (after ramification) into elementary factors easy to work with. This decomposition may not hold at some other points of D. When it does, we say that M has good formal decomposition along D. A conjecture of Sabbah, recently proved by Kedlaya and Mochizuki independently, asserts roughly the
2017 Dec 19

T&G: Yakov Eliashberg (Stanford), Simplifying singularities of Lagrangian skeleta

1:00pm to 2:30pm

Location: 

Room 63, Ross Building, Jerusalem, Israel
I will discuss in the talk David Nadler’s “arborealizaton conjecture” and will sketch its proof. The conjecture states that singularities of a Lagrangian skeleton of a symplectic Weinstein manifold could be always simplified to a finite list of singularities, called ``arboreal”. This is a joint work with Daniel Albarez-Gavela, David Nadler and Laura Starkston.
2015 Nov 05

Groups & Dynamics : Ilya Khayutin (HUJI)

9:45am to 11:00am

Location: 

Manchester building, Hebrew University of Jerusalem, (Room 209)
Title: Arithmetic of Double Torus Quotients and the Distribution of Periodic Torus Orbits Abstract: In this talk I will describe some new arithmetic invariants for pairs of torus orbits on inner forms of PGLn and SLn. These invariants allow us to significantly strengthen results towards the equidistribution of packets of periodic torus orbits on higher rank S-arithmetic quotients. An important aspect of our method is that it applies to packets of periodic orbits of maximal tori which are only partially split.
2016 Jun 02

Groups & dynamics: Todor Tsankov (Paris-Diderot): On metrizable universal minimal flows

10:00am to 11:00am

Location: 

Ross building, Hebrew University of Jerusalem, (Room 70)
To every topological group, one can associate a unique universal minimal flow (UMF): a flow that maps onto every minimal flow of the group. For some groups (for example, the locally compact ones), this flow is not metrizable and does not admit a concrete description. However, for many "large" Polish groups, the UMF is metrizable, can be computed, and carries interesting combinatorial information. The talk will concentrate on some new results that give a characterization of metrizable UMFs of Polish groups. It is based on two papers, one joint
2015 Dec 17

Groups & dynamics: Rene Rühr, Distribution of Shapes of Orthogonal Lattices

10:00am to 11:30am

Location: 

Ross building, Hebrew University of Jerusalem, (Room 70)
To every topological group, one can associate a unique universal minimal flow (UMF): a flow that maps onto every minimal flow of the group. For some groups (for example, the locally compact ones), this flow is not metrizable and does not admit a concrete description. However, for many "large" Polish groups, the UMF is metrizable, can be computed, and carries interesting combinatorial information. The talk will concentrate on some new results that give a characterization of metrizable UMFs of Polish groups. It is based on two papers, one joint
2017 Dec 12

T&G: Yoel Groman (Columbia), Generation of the Fukaya category of a Lagrangian torus fibration by a section

1:00pm to 2:30pm

Location: 

Room 70A, Ross Building, Jerusalem, Israel
The (wrapped) Fukaya category of a symplectic manifold is a category whose objects are Lagrangian submanifolds and which contains a wealth of information about the symplectic topology. I will discuss the construction of the wrapped Fukaya category for certain completely integrable Hamiltonian systems. These are 2n-dimensional symplectic manifolds carrying a system of n commuting Hamiltonians surjecting onto Euclidean space. This gives rise to a Lagrangian torus fibration with singularities.

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