Title

Quantum cohomology of toric bundles

Date

April 30 (Tuesday), 13:00--14:30, 2024

Place

Room 011, RIMS

Speaker

Yuki Koto

Title

Realization of A^{(1)*}_2-surfaces as the moduli spaces of connections

Date

April 17 (Wed), 13:30--15:00, 2024

Place

Room 206, RIMS

Speaker

Takafumi Matsumoto (RIMS)

Title

On the WKB approximation and the Riemann-Hilbert problem of meromorphic linear systems with Poncaré rank 1.

Date

August 18 (Friday), 10:00--12:00, 2023

Place

Room 006, RIMS

Speaker

Xiaomeng Xu (Peking University)

Abstract

This talk first gives an introduction to the Stokes matrices of meromorphic linear systems with Poncaré rank 1. It then express explicitly the Stokes matrices via the leading asymptotics of solutions of the associated isomonodromy equation at a critical point. Such an expression of Stokes matrices can be understood as a perfect analytic model from various perspective. In particular, the expression is used to study the WKB approximation of the Stokes matrices, and its relation with Cauchy interlace inequalities, the spectral network and so on. If time allows, the talk discusses the WKB approximation and Stokes matrices of a quantum meromorphic linear systems with Poncaré rank 1, with a relation to quantum groups and crystal basis.

Title

Wall-crossing for framed quiver moduli

Date

May 12 (Thu), 17:00-18:30, 2022

Room

Zoom

Speaker

Ryo Ohkawa (Osaka Metropolitan University)

Title

Stokes filtered sheaves and differential-difference modules

Date

September 10 (Thu), 13:30-15:30, 2020

Room

Zoom

Speaker

Yota Shamoto (Kavli IPMU)

Title

Sheaves and symplectic geometry of cotangent bundles

Date

February 19 (Mon), 10:00-12:00, 15:00-17:00, 2018
February 20 (Tue), 10:00-12:00, 15:00-17:00, 2018

Room

RIMS, Rm 110

Speaker

Stéphane Guillermou (Université Grenoble Alpes Institut Fourier)

Abstract

We will explain how the microlocal theory of sheaves, introduced by Kashiwara and Schapira in the 80's, is used in symplectic geometry (mainly of cotangent bundles), since works of Nadler-Zaslow and Tamarkin in 2008. In particular we will sketch a proof of the following result: a compact exact Lagrangian submanifold of a cotangent bundle $T^*M$ is homotopically equivalent to the base $M$, through the natural projection from $T^*M$ to $M$.
The lectures will be a more detailed exposition of the topics introduced in the first talk (Feb. 2):
-- (constructible) sheaves and microsupport; operations
-- sheaves associated with a Hamiltonian isotopy of a cotangent bundle; first applications (maybe the non squeezing lemma)
-- Sato's microlocalization and the muhom functor
-- study of compact exact Lagrangian submanifolds of a cotangent bundle.

Title

Sheaves and symplectic geometry of cotangent bundles

Date

February 2 (Fri), 15:00-17:00, 2018

Room

RIMS, Rm 110

Speaker

Stéphane Guillermou (Université Grenoble Alpes Institut Fourier)

Abstract

We will explain how the microlocal theory of sheaves, introduced by Kashiwara and Schapira in the 80's, is used in symplectic geometry (mainly of cotangent bundles), since works of Nadler-Zaslow and Tamarkin in 2008. In particular we will sketch a proof of the following result: a compact exact Lagrangian submanifold of a cotangent bundle $T^*M$ is homotopically equivalent to the base $M$, through the natural projection from $T^*M$ to $M$.
In the course of the talk we will quickly recall the main notions of the microlocal theory of sheaves and give examples.

Title

Period maps, spectral numbers and Stokes matrices of isolated hypersurface singularities.

Date

July 6 (Thu), 15:00-17:00, 2017
July 7 (Fri), 15:00-17:00, 2017

Room

RIMS, Rm 111

Speaker

Claus Hertling (University of Mannheim)

Abstract

Holomorphic function germs with isolated singularities have been studied since the end of the 1960ies. A lot is known about their topology, their Milnor lattices, their Gauss-Manin connections and induced Hodge structures, and the behaviour of these data in families of functions. But also a lot is still not well understood, basic properties of the integral monodromy and Seifert form, a mysteriously well working interplay between lattice data and period maps for families, the spectral numbers.
The talk will give an introduction to the playing characters in the theory of isolated hypersurface singularities and will present a bouquet of old and new conjectures and related results. The first talk will focus on single singularities and mu-constant families, the second talk on universal unfoldings and Stokes structures of generic members.
For unmarked as well as marked singularities, moduli spaces, period maps, Torelli conjectures and Torelli results will be presented. An old conjecture on the integral monodromy of quasihomogeneous singularities will be recalled. Results and conjectures on the spectral numbers will be given. This will be useful for a conjectural characterization of the Stokes matrices and Coxeter-Dynkin diagrams of singularities.

Title

Topological recursion, WKB analysis and Painlevé equations

Date

June 22 (Thu), 13:30-15:30, 2017

Room

RIMS, Rm 006

Speaker

Kohei Iwaki (Nagoya University)

Title

Differential equations and algebraic points on transcendental varieties

Date

April 6 (Thu), 13:30-15:00, 2017

Room

RIMS, Rm 110

Speaker

Gal Binyamini (Weizmann Institute)

Abstract

The problem of bounding the number of rational or algebraic points of a given height in a transcendental set has a long history. In 2006 Pila and Wilkie made fundamental progress in this area by establishing a sub-polynomial asymptotic estimate for a very wide class of transcendental sets. This result plays a key role in Pila-Zannier's proof of the Manin-Mumford conjecture, Pila's proof of the Andre-Oort conjecture for modular curves, Masser-Zannier's work on torsion anomalous points in elliptic families, and many more recent developments. I will briefly sketch the Pila-Wilkie theorem and the way it enters into the arithmetic applications. I will then discuss recent work on an effective form of the Pila-Wilkie theorem (for certain sets) which leads to effective versions of many of the applications. I will also discuss a joint work with Dmitry Novikov on sharpening the asymptotic from sub-polynomial to poly-logarithmic for certain structures, leading to a proof of the restricted Wilkie conjecture. The structure of the systems of differential equations satisfied by various transcendental functions play the main role for both of these directions.

Title

Filtered holonomic D-modules in dimension one

Date

December 1 (Thu), 15:00-17:00, 2016
December 2 (Fri), 15:00-17:00, 2016

Room

RIMS, Rm 110

Speaker

Claude Sabbah

Abstract

Holonomic D-modules on the affine complex line offer a simple prototype of various properties also occurring in higher dimensions. We will focus on filtered holonomic D-modules from various points of view.

In the first lecture, we start from a filtered regular holonomic D-module M underlying a Hodge module, and we explain the construction an some properties of the associated Deligne filtration on the D-module obtained from M by applying an exponential twist. This is strongly related to considering the Laplace transform of M. We will give motivations for considering such a filtration.

In the second lecture, we focus on rigid irreducible holonomic D-modules on the affine line. Generic (possibly confluent) hypergeometric differential equations give naturally rise to examples of such objects. After having explained the Katz algorithm (respectively the Arinkin-Deligne algorithm) for reducing the regular (respectively possibly irregular) such D-modules to ones having generic rank one, we will consider the behaviour of Hodge (respectively Deligne) filtrations along the algorithm (joint work with M. Dettweiler) and we will explain some examples.