## Upcoming conferences & activities

## Higher Geometric Structures along the Lower Rhine XIV, March 12 - 13, 2020

This is the fourteenth of a series of short workshops jointly organized by the Geometry/Topology groups in Bonn, Nijmegen, and Utrecht, all situated along the Lower Rhine. The focus lies on the development and application of new structures in geometry and topology such as Lie groupoids, differentiable stacks, Lie algebroids, generalized complex geometry, topological quantum field theories, higher categories, homotopy algebraic structures, higher operads, derived categories, and related topics.

## A room of one's own. Writing workshop at MPIM

Do you have a paper in progress that you think you could finish if only you had an uninterrupted weekend to work on it? Do you struggle with carving out the time that you need because of childcare responsibilities at home, or because you are swamped with teaching and administrative duties at work? Click here for information on how you can apply to spend the weekend of April 24 - 26 at the Max Planck Institute for Mathematics finishing that paper!

For more information and application go here.

## Geometric Representation Theory

## Twinned conference "Geometric Representation Theory", June 22 - 26, 2020

This will be a twinned conference held simultaneously at Max Planck Institute in Bonn, Germany and Perimeter Institute in Waterloo, Canada. The two venues will be connected by live video streams, during both the talks themselves as well as informal discussion sessions.

## Workshop on "$\infty$-categories and their applications", August 17 - 21, 2020

The quest for solid foundations for $\infty$-categories started several decades ago, but from the mid-2000s there have been spectacular developments which excitingly accelerated the pace of progress. This workshop will focus on these objects, both in their foundations and in the applications to different fields of mathematics. There will be minicourses on $\infty$-categories, and also on $\infty$-operads, on algebraic K-theory and on parametrized homotopy theory, all three of which have benefited substantially from the $\infty$-categorical viewpoint.

## Upcoming Talks

Abstracts of upcoming talks at the MPIM. For an overview see also the calendar.

## Recent developments in Quantum Topology -- Cancelled --

We will review the basics of quantum topology such as the colored Jones polynomial of a knot, its standard conjectures relating to asymptotics, arithmeticity and modularity, as well as the recent quantum hyperbolic invariants of Kashaev et al, their state-integrals and their structural properties. The course is aimed to be accessible by graduate students and young researchers.

## Quantum group symmetry in CFT

I discuss applications of a hidden $U_q({sl}_2)$ symmetry in CFT with central charge $c \leq 1$ (focusing on the generic, semisimple case, withcirrational). This symmetry provides a systematic method for solving Belavin-Polyakov-Zamolodchikov PDE systems, and in partic-ular for explicit calculation of the asymptotics and monodromy properties of the solutions.Using a quantum Schur-Weyl duality, one can understand solution spaces of such PDE systems in a detailed way.

## On the representation of binary quadratic forms by quadratic forms

Let $Q$ and $T$ denote two matrices that represent positive integral quadratic forms. We are investigating the solubility of $X^T Q X = T$ for an integer matrix $X$. Therefore, we consider the Siegel theta series of degree two and derive an asymptotic formula for its Fourier coefficients in the level aspect. This involves computing inner-products of the cuspidal part of theta series and evaluating Fourier coefficients of Eisenstein-Klingen series.

## Braids

## Complex-valued harmonic morphisms from Lie groups and symmetric Spaces

The study of harmonic morphisms in the 3-dimensional Euclidean space goes back to a paper of Jacobi from 1848. This was then introduced into the setting of Riemannian geometry, in the late 1970s by Fuglede and Ishihara, independently. A harmonic morphism between two Riemannian manifolds (M, g) and (N, h) is a map that pulls back real-valued harmonic functions on (N,h) to harmonic functions on (M,g).

## New guests at the MPIM

## tba

## Free subgroups of Kleinian groups

We show that any cocompact Kleinian group $\Gamma$ has an exhaustive filtration by normal subgroups $\Gamma_i$ such that any subgroup of $\Gamma_i$ generated by $k_i$ elements is free, where $k_i \ge [\Gamma:\Gamma_i]^C$ and $C = C(\Gamma) > 0$. Together with this result we prove that $\log k_i \ge C_1 \mathrm{sys}_1(M_i)$, where $\mathrm{sys}_1(M_i)$ denotes the systole of $M_i$, thus providing a large set of new examples for a conjecture of Gromov. In the second theorem $C_1> 0$ is an absolute constant.

## Absolute algebraic geometry using gamma sets, after A.Connes and C.Consani

This is an expository talk on Connes-Consani's theory of geometry over field with one element. It is based on Segal's theory of gamma sets (see arXiv:1502.05585 [math.AG]). I will explain the background, the basic constructions and some interesting examples.

## Foliated Open Books -- or, How I Learned to Stop Worrying About How to Glue Open Books, I

In this talk, I'll discuss recent joint work with Vera Vertesi to develop a new version of an open book decomposition for contact three-manifolds. Our foliated open books join a zoo of existing types of open books, so I'll focus on the senses in which ours is a natural construction which provides a user-friendly approach to cutting and gluing.

## Mathematical events in Bonn

##### Bonn Mathematics Calendar

All mathematical events in Bonn are listed in the Bonn Mathematics Calendar. For directions see the map.

##### University Calendar

All lectures and courses at Bonn University can be found in the university calendar.

## Recurring seminars, series and courses

Detailed list of recurring seminars, series of talks, and courses or lectures comprising multiple talks. For an overview see also the calendar.

## Friedrich Hirzebruch Lecture

The annual Friedrich Hirzebruch Lecture is a series of lectures started in 2007 on the occasion of the 80th birthday of Prof. Friedrich Hirzebruch. The lectures address a general audience and aim at illustrating the relation between mathematics and art, society and other fields.

## MPI-Oberseminar

The Oberseminar is a very long running seminar at MPI (‘Ober‘ standing for 'upper'). Its idea is that the guests of the MPI speak in this seminar (hopefully early in their stay) and get the chance to explain their work to the other guests.

## IMPRS Minicourse

## IMPRS seminar on various topics: Hitchin systems

## Representation theory learning seminar

## Extra talk

## A study group on Milnor invariants

## Archived Events

To narrow the list of events displayed please select year and event type or fill the search fields, then press *Apply*.

## MPI-Oberseminar

The Oberseminar is a very long running seminar at MPI (‘Ober‘ standing for 'upper'). Its idea is that the guests of the MPI speak in this seminar (hopefully early in their stay) and get the chance to explain their work to the other guests.

## Friedrich Hirzebruch Lecture

The annual Friedrich Hirzebruch Lecture is a series of lectures started in 2007 on the occasion of the 80th birthday of Prof. Friedrich Hirzebruch. The lectures address a general audience and aim at illustrating the relation between mathematics and art, society and other fields.

## Workshop on "$\infty$-categories and their applications", August 17 - 21, 2020

The quest for solid foundations for $\infty$-categories started several decades ago, but from the mid-2000s there have been spectacular developments which excitingly accelerated the pace of progress. This workshop will focus on these objects, both in their foundations and in the applications to different fields of mathematics. There will be minicourses on $\infty$-categories, and also on $\infty$-operads, on algebraic K-theory and on parametrized homotopy theory, all three of which have benefited substantially from the $\infty$-categorical viewpoint.

## Geometric Representation Theory

## Twinned conference "Geometric Representation Theory", June 22 - 26, 2020

This will be a twinned conference held simultaneously at Max Planck Institute in Bonn, Germany and Perimeter Institute in Waterloo, Canada. The two venues will be connected by live video streams, during both the talks themselves as well as informal discussion sessions.

## tba

## A room of one's own. Writing workshop at MPIM

Do you have a paper in progress that you think you could finish if only you had an uninterrupted weekend to work on it? Do you struggle with carving out the time that you need because of childcare responsibilities at home, or because you are swamped with teaching and administrative duties at work? Click here for information on how you can apply to spend the weekend of April 24 - 26 at the Max Planck Institute for Mathematics finishing that paper!

For more information and application go here.

## tba

## tba

## Reading group on geometric group theory

## Special cycles on orthogonal Shimura varieties

Extending on the work of Kudla-Millson and Yuan-Zhang-Zhang, together with Yott we are constructing special cycles for a specific orthogonal Shimura variety. We further construct a generating series that has as coefficients the cohomology classes corresponding to

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