# Talk

Talks and seminars, possibly part of a conference or series.

## Beauville decomposition: proof via Fourier-Mukai

Posted in
Speaker:
Mingjia Zhang
Zugehörigkeit:
Universität Bonn/MPIM
Datum:
Don, 2021-02-04 14:15 - 15:45

Meeting ID: 997 9940 1217
For passcode contact Christian Kaiser (kaiser@mpim...)

## Lie algebra action

Posted in
Speaker:
Till Wehrhan
Zugehörigkeit:
Universität Bonn/MPIM
Datum:
Don, 2021-01-28 14:15 - 15:45

Meeting ID: 997 9940 1217
For passcode contact Christian Kaiser (kaiser@mpim...)

## Chow rings and abelian varieties

Posted in
Speaker:
Grigory Andreychev
Zugehörigkeit:
Universität Bonn/MPIM
Datum:
Don, 2021-01-21 14:15 - 15:45

Meeting ID: 997 9940 1217
For passcode contact Christian Kaiser (kaiser@mpim...)

## tba

Posted in
Speaker:
Rosa Schwarz
Zugehörigkeit:
Leiden University
Datum:
Mon, 2021-01-25 10:30 - 12:00

## Properties of obstruction theories and virtual classes

Posted in
Speaker:
Reinier Kramer
Zugehörigkeit:
MPIM
Datum:
Mon, 2021-01-18 10:30 - 12:00

After a recap of last week's constructions of perfect obstruction theories and virtual fundamental classes, I will discuss their properties with respect to deformation, and construct virtual pullbacks, which are bivariant classes. Then I will discuss the behaviour of virtual classes under pushforwards and give computational examples.

## Second moment of the central values of Rankin--Selberg $L$-functions

Posted in
Speaker:
Subhajit Jana
Zugehörigkeit:
MPIM
Datum:
Mit, 2021-01-20 14:30 - 15:30
Parent event:
Number theory lunch seminar

Asymptotic evaluation of higher moments of higher degree $L$-values is an interesting problem and has potential applications towards many questions in analytic theory of automorphic forms, e.g. subconvexity of the central $L$-values. In this talk I will explain a recent result on asymptotic evaluation of the second moment of $\mathrm{GL}(n) \times \mathrm{GL}(n)$ Rankin--Selberg central $L$-values where one of the forms is a fixed cuspidal representation and the other form is varying in a family containing representations with analytic conductors bounded by $X$ and $X \to \infty$.

## Holomorphic curves, boundaries, skeins, and recursion

Posted in
Speaker:
Vivek Shende
Zugehörigkeit:
SDU Odense/Berkeley
Datum:
Die, 2021-02-16 14:00 - 15:30

I will explain how to define all genus open Gromov-Witten invariants for Calabi-Yau 3-folds.  The key idea is to count curves by their boundary in the skein modules of Lagrangians. Then I will prove the assertion of Ooguri and Vafa that the colored HOMFLYPT polynomials of a knot are exactly the counts of holomorphic curves in the resolved conifold with boundary on a Lagrangian associated to the knot.  In the process we will see the geometric origin of recursion relations for colored knot invariants.  This talk presents joint work with Tobias Ekholm.

## Non-abelian Abel's theorems and quaternionic rotation

Posted in
Speaker:
Vasily Golyshev
Zugehörigkeit:
MCCME, Moscow/MPIM
Datum:
Die, 2021-02-23 14:00 - 15:30

I will talk on a subject which has evolved over the years in discussions with M. Kontsevich, A. Mellit, V. Roubtsov, and D. van Straten.

## Macroscopic band width inequalities

Posted in
Speaker:
Daniel Räde
Zugehörigkeit:
Universität Augsburg
Datum:
Don, 2021-01-14 16:30 - 18:00

Inspired by Gromov's work on 'Metric inequalities with scalar
curvature' we establish band width inequalities for Riemannian bands of
the form $(V=M\times[0,1],g)$, where $M^{n-1}$ is a closed manifold. We
introduce a new class of orientable manifolds we call 'filling
enlargeable' and prove:
If $M$ is filling enlargeable and all unit balls in the universal cover
of $(V,g)$ have volume less than a constant $\frac{1}{2}\epsilon_n$, then $width(V,g)\leq1$.
We show that if a closed orientable manifold is enlargeable or

## Topological expansions, Random matrices and operator algebras theory

Posted in
Speaker:
Alice Guionnet
Zugehörigkeit:
ENS Lyon
Datum:
Die, 2021-01-19 14:00 - 15:30

In this lecture, I will discuss the remarkable connection between random
matrices and the enumeration of maps and some applications to sub-factor theory and  physics.
https://hu-berlin.zoom.us/j/61339297016

## Topological expansions, Random matrices and operator algebras theory

Posted in
Speaker:
Alice Guionnet
Zugehörigkeit:
ENS Lyon
Datum:
Die, 2021-01-19 14:00 - 15:00

In this lecture, I will discuss the remarkable connection between random
matrices and the enumeration of maps and some applications to sub-factor theory and  physics.
https://hu-berlin.zoom.us/j/61339297016

## tba

Posted in
Speaker:
Gunja Sachdeva
Zugehörigkeit:
Indian Institute of Science Education and Research/MPIM
Datum:
Mit, 2021-01-27 14:30 - 15:30
Parent event:
Number theory lunch seminar

Zoom Meeting ID: 919 6497 4060
For password see the email or contact Pieter Moree (moree@mpim...).

## Defining perfect obstruction theories and virtual fundamental classes

Posted in
Speaker:
Nitin Chidambaram
Zugehörigkeit:
MPIM
Datum:
Mon, 2021-01-11 10:30 - 12:00

I will talk about obstruction bundles and use them to give a preliminary definition of virtual fundamental classes. We will use this notion to compute the virtual fundamental class explicitly in some examples. Then, we will define virtual fundamental classes more generally as in Behrend-Fantechi using the notion of perfect obstruction theories.

## Mock Modular Forms

Posted in
Speaker:
Matthias Storzer
Zugehörigkeit:
MPIM
Datum:
Don, 2021-01-14 14:15 - 15:45

Meeting ID: 997 9940 1217
For passcode contact Christian Kaiser (kaiser@mpim...).

## Maass Forms and 2-dimensional Artin Representations

Posted in
Speaker:
Kilian Boenisch
Zugehörigkeit:
MPIM
Datum:
Don, 2021-01-07 14:15 - 15:45

Meeting ID: 997 9940 1217
For passcode contact Christian Kaiser (kaiser@mpim...).

## Dynamical irreducibility of polynomials modulo primes

Posted in
Speaker:
Alina Ostafe
Zugehörigkeit:
University of New South Wales, Sydney
Datum:
Mit, 2021-01-13 13:30 - 14:30
Parent event:
Number theory lunch seminar

Zoom ID: 919 6497 4060
For password contact Pieter Moree (moree@mpim...).

## tba

Posted in
Speaker:
Alina Ostafe
Zugehörigkeit:
University of New South Wales, Sydney
Datum:
Mon, 2020-01-13 14:30 - 15:30
Parent event:
Number theory lunch seminar

## Prismatic cohomology of classifying stacks

Posted in
Speaker:
Dmitry Kubrak
Zugehörigkeit:
MPIM
Datum:
Mon, 2020-12-21 14:30 - 14:50
Parent event:
MPIM Topology Seminar

I will tell about the theory of prismatic cohomology (developed recently by Bhatt and Scholze) and what it gives when applied to the classifying stack of a reductive group.

## Khovanov homology and invariants of 4-manifolds

Posted in
Speaker:
Paul Wedrich
Zugehörigkeit:
MPIM
Datum:
Mon, 2020-12-21 14:00 - 14:20
Parent event:
MPIM Topology Seminar

Roughly twenty years ago, two homology theories for knots and links were developed, which can be seen as categorifications of the Alexander polynomial and the Jones polynomial. Knot Floer homology is derived from the Heegaard--Floer 3-manifold invariants, while Khovanov homology has its origin in the (higher) representation theory of quantum groups. It is a natural question, whether Khovanov homology also has an associated manifold invariant. In this talk I will sketch the construction of a candidate Khovanov homology for 4-manifolds''.

## A multi-Frey approach to the Darmon program for the Generalized Fermat Equation

Posted in
Speaker:
Nunos Freitas
Zugehörigkeit:
University of Barcelona/MPIM
Datum:
Mit, 2020-12-16 14:30 - 15:30
Parent event:
Number theory lunch seminar

In 2000, Darmon described a remarkable program to study the Generalized
Fermat equation Ax^r + By^q = Cz^p using modularity of abelian varieties
of GL_2-type over totally real fields. However, his program relies on hard
open conjectures, which has made it difficult to apply in practice, and so
far the only successes were in cases where the Frey varieties are elliptic
curves.

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