## Upcoming conferences & activities

## Metric Measure Spaces and Ricci Curvature

## Hirzebruch colloquium talk by Walter Neumann

## "Descartes, Euler, Gauss: From surfaces to integers". Hirzebruch lecture by Werner Ballmann on Monday, November 13

Geometric quantities of a surface, like distance, angle, or area, change when the surface is deformed. Euler discovered a quantity, the Euler characteristic, which remains unchanged. The formula of Gauss-Bonnet, a landmark result of mathematics, relates Euler characteristic with geometry. In the talk, I will present ideas of Descartes, Euler, and Gauss related to this formula.

## 3rd Japanese-German Number Theory Workshop, November 20 - 24, 2017

**3rd Japanese-German Number Theory Workshop**

**November 20 - 24, 2017**

Here you can find the official homepage

#### Organizers

- German Organizers : Jonas Kaszian (University of Cologne), Pieter Moree (MPIM)
- Japanese Organaizers : Hiroki Aoki (Tokyo University of Science), Koji Tasaka (MPIM/Aichi Prefectural University)

#### Speakers

Sho Takemori (MPIM)

Tomomi Ozawa (Univ. Paris 13)

Kenji Makiyama (Kyoto Sangyo Univ.)

Ren-he Su (Kyoto Univ.)

Nobuo Sato (Kyoto Univ.)

Hiraku Atobe (Tokyo Univ.)

Shingo Sugiyama (Kyushu Univ.)

Minoru Hirose (Kyushu Univ.)

Toshiki Matsusaka (Kyushu Univ.)

Shun'ichi Yokoyama (Kyushu Univ.)

Hiroshi Sakata (Waseda Univ Senior High School)

Hidetaka Kitayama (Wakayama Univ.)

Hiro-aki Narita (Kumamoto Univ.)

Takashi Nakamura (Tokyo Univ. of Science)

Shuichi Hayashida (Joetsu Univ. of Education)

Hiroki Aoki (Tokyo Univ. of Science)

Claudia Alfes-Neumann (University of Cologne)

Jan Bruinier (TU Darmstadt)

Steffen Löbrich (University of Cologne)

Markus Schwagenscheidt (TU Darmstadt)

Annalena Wernz (RWTH Aachen)

## Workshop "Young Researchers in String Mathematics", November 27 - 30, 2017

**Workshop "Young Researchers in String Mathematics"**

**November 27 - 30, 2017**

The workshop is an occasion to foster interactions and initiate new collaborations between young researchers active in Germany and nearby countries, who are all interested in mathematical aspects of string theory: mirror symmetry, enumerative geometry of curves (Gromov-Witten theory, Donaldson-Thomas, stable pair invariants, ...) and their modularity, integrability, and algebraic properties, tropical geometry, topological recursion, wall-crossing phenomena and Bridgeland stability conditions, relations to gauge theory, geometric quantization, conformal field theory, etc.

#### Organizers

Murad Alim (Universität Hamburg) and Gaëtan Borot (MPIM)

#### Speakers

Murad Alim (Universität Hamburg)

Gaëtan Borot (MPIM)

Andrea Brini* (CNRS Montpellier/Imperial College)

Miranda Cheng (University of Amsterdam)

Sara Angela Filippini (Cambridge University)

Michel van Garrel (Universität Hamburg)

Owen Gwilliam (MPIM)

Lotte Hollands (Heriot-Watt University, Edimburgh)

Victoria Hoskins (Humboldt Universität, Berlin)

Hans Jockers (Universität Bonn)

Christian Lehn (Universität Chemnitz)

Jan Manschot (Trinity College Dublin)

Elli Pomoni (DESY Hamburg)

Johannes Rau (Universität Tübingen)

Thomas Reichelt (Universität Heidelberg)

Helge Ruddat (Universität Mainz)

Sarah Scherotzke (Bristol University)

Maxim Smirnov (Universität Augsburg/MPIM)

Piotr Sułkowski (University of Warsaw)

Di Yang (MPIM)

* = to be confirmed

## Conference on Arithmetic and Automorphic Forms on the occasion of Günter Harder's 80th birthday, March 12 - 14, 2018

**Conference on **

**Arithmetic and Automorphic Forms **

**on the occasion of Günter Harder's 80th birthday**

**March 12 - 14, 2018**

#### Scientific Committee

Werner Ballmann, Michael Rapoport, and Joachim Schwermer

#### Local Organizer

Werner Ballmann and Christian Blohmann

#### Speakers

Kai Behrend (U British Columbia)

Spencer Bloch (U Chicago)

Gaetan Chenevier (U Paris-Sud, Orsay)

Mark Goresky (IAS Princeton)

Tasho Kaletha (U Michigan)

Stephen S. Kudla (U Toronto)

Richard Pink (ETH Zürich)

Anantharam Raghuram (IISER Pune)

Andrei Rapinchuk (U Virginia)

Peter Scholze (U Bonn)

Carlos Simpson (U Nice)

Gerard van der Geer (U Amsterdam)

## Upcoming Talks

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

## Seminar on Kac-Moody algebras and related topics

## The Globalization Theorem for the Curvature-Dimension Condition

The Lott-Sturm-Villani Curvature-Dimension condition provides a synthetic notion for a metric-measure space to have Ricci-curvature bounded from below and dimension bounded from above.

## Differential calculus on RCD spaces - part 1

In the lecture I will survey recent advances on calculus on RCD spaces. I shall start recalling how the concept of `L2-normed L1 module' allows to give a reasonable definition of

(co)tangent space and to build a first-order theory on abstract metric measure spaces. The Bochner inequality, which properly interpreted defines RCD spaces, will then allow

to build a second order calculus in such setting: we shall review it and, if time permits, see some applications to the study of geometry of RCD spaces.

## Non-commutative transport metrics, gradient flow and functional inequalities - part 2

The space of positive semi-definite $n\times n$ matrices with unit trace, or more generally, the space of states on a $C^*$ algebra can be made into a metric space using constructions that a analogous to the transportation-theoretic constructions that make spaces of probability measures into metric spaces.

## A categorical approach to universal knot invariants

## Quantitative Isoperimetry à la Levy-Gromov

On a Riemannian manifold with a positive lower bound on the Ricci tensor, the distance of isoperimetric sets from geodesic balls is quantitatively controlled in terms of the gap between the isoperimetric profile of the manifold and that of a round sphere of suitable radius. The deficit between the diameters of the manifold and of the corresponding sphere is bounded likewise.

## Harmonic maps between Riemannian manifolds

## Differential calculus on RCD spaces - part 2

In the lecture I will survey recent advances on calculus on RCD spaces. I shall start recalling how the concept of `L2-normed L1 module' allows to give a reasonable definition of

(co)tangent space and to build a first-order theory on abstract metric measure spaces. The Bochner inequality, which properly interpreted defines RCD spaces, will then allow

to build a second order calculus in such setting: we shall review it and, if time permits, see some applications to the study of geometry of RCD spaces.

## Isometry groups of spaces with lower ricci curvature bounds

Isometric actions on Riemannian manifolds have been a usefu tool to investigate the interaction between the topology and the Riemannian metric a manifold might admit. A major result in the area is the theorem of Myers-Steenrod [4] stating that the isometry group of a Riemannian manifold is a Lie group. Later this result has been extended to a wider class of spaces with certain synthetic notions of curvature bounds such as Alexandrov spaces by Fukaya-Yamaguchi [2] and limits of manifolds with lower Ricci curvature bounds by Cheeger-Colding [1].

## Markovian representation of the continuity equation

It has been established by Lisini that absolutely continuous curves (of order 2) $\mu:t ↦ \mu_t$ in the Wasserstein space over a metric space $X$ can be represented by an action-minimizing probability measure on the space of absolutely continuous curves. We will show that in the basic case of the real line ($X=\mathbb{R}$), this measure can moreover be asked to be Markovian. This is a special case of a more general result, with other consequences, where no continuity assumptions are made on the family $\mu$. (joint work with Charles Boubel)

## 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.

## Number theory lunch seminar

The number theory lunch seminar takes place every Wednesday after a joint lunch of MPIM's number theorists...

## IMPRS Minicourse

## Extra talk

## Seminar on Algebra, Geometry and Physics

## Seminar Algebraic Geometry (SAG)

## Higher Differential Geometry Seminar

## 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.

## Conference on Arithmetic and Automorphic Forms on the occasion of Günter Harder's 80th birthday, March 12 - 14, 2018

**Conference on **

**Arithmetic and Automorphic Forms **

**on the occasion of Günter Harder's 80th birthday**

**March 12 - 14, 2018**

#### Scientific Committee

Werner Ballmann, Michael Rapoport, and Joachim Schwermer

#### Local Organizer

Werner Ballmann and Christian Blohmann

#### Speakers

Kai Behrend (U British Columbia)

Spencer Bloch (U Chicago)

Gaetan Chenevier (U Paris-Sud, Orsay)

Mark Goresky (IAS Princeton)

Tasho Kaletha (U Michigan)

Stephen S. Kudla (U Toronto)

Richard Pink (ETH Zürich)

Anantharam Raghuram (IISER Pune)

Andrei Rapinchuk (U Virginia)

Peter Scholze (U Bonn)

Carlos Simpson (U Nice)

Gerard van der Geer (U Amsterdam)

## Workshop "Young Researchers in String Mathematics", November 27 - 30, 2017

**Workshop "Young Researchers in String Mathematics"**

**November 27 - 30, 2017**

The workshop is an occasion to foster interactions and initiate new collaborations between young researchers active in Germany and nearby countries, who are all interested in mathematical aspects of string theory: mirror symmetry, enumerative geometry of curves (Gromov-Witten theory, Donaldson-Thomas, stable pair invariants, ...) and their modularity, integrability, and algebraic properties, tropical geometry, topological recursion, wall-crossing phenomena and Bridgeland stability conditions, relations to gauge theory, geometric quantization, conformal field theory, etc.

#### Organizers

Murad Alim (Universität Hamburg) and Gaëtan Borot (MPIM)

#### Speakers

Murad Alim (Universität Hamburg)

Gaëtan Borot (MPIM)

Andrea Brini* (CNRS Montpellier/Imperial College)

Miranda Cheng (University of Amsterdam)

Sara Angela Filippini (Cambridge University)

Michel van Garrel (Universität Hamburg)

Owen Gwilliam (MPIM)

Lotte Hollands (Heriot-Watt University, Edimburgh)

Victoria Hoskins (Humboldt Universität, Berlin)

Hans Jockers (Universität Bonn)

Christian Lehn (Universität Chemnitz)

Jan Manschot (Trinity College Dublin)

Elli Pomoni (DESY Hamburg)

Johannes Rau (Universität Tübingen)

Thomas Reichelt (Universität Heidelberg)

Helge Ruddat (Universität Mainz)

Sarah Scherotzke (Bristol University)

Maxim Smirnov (Universität Augsburg/MPIM)

Piotr Sułkowski (University of Warsaw)

Di Yang (MPIM)

* = to be confirmed

## 3rd Japanese-German Number Theory Workshop, November 20 - 24, 2017

**3rd Japanese-German Number Theory Workshop**

**November 20 - 24, 2017**

Here you can find the official homepage

#### Organizers

- German Organizers : Jonas Kaszian (University of Cologne), Pieter Moree (MPIM)
- Japanese Organaizers : Hiroki Aoki (Tokyo University of Science), Koji Tasaka (MPIM/Aichi Prefectural University)

#### Speakers

Sho Takemori (MPIM)

Tomomi Ozawa (Univ. Paris 13)

Kenji Makiyama (Kyoto Sangyo Univ.)

Ren-he Su (Kyoto Univ.)

Nobuo Sato (Kyoto Univ.)

Hiraku Atobe (Tokyo Univ.)

Shingo Sugiyama (Kyushu Univ.)

Minoru Hirose (Kyushu Univ.)

Toshiki Matsusaka (Kyushu Univ.)

Shun'ichi Yokoyama (Kyushu Univ.)

Hiroshi Sakata (Waseda Univ Senior High School)

Hidetaka Kitayama (Wakayama Univ.)

Hiro-aki Narita (Kumamoto Univ.)

Takashi Nakamura (Tokyo Univ. of Science)

Shuichi Hayashida (Joetsu Univ. of Education)

Hiroki Aoki (Tokyo Univ. of Science)

Claudia Alfes-Neumann (University of Cologne)

Jan Bruinier (TU Darmstadt)

Steffen Löbrich (University of Cologne)

Markus Schwagenscheidt (TU Darmstadt)

Annalena Wernz (RWTH Aachen)

## "Descartes, Euler, Gauss: From surfaces to integers". Hirzebruch lecture by Werner Ballmann on Monday, November 13

Geometric quantities of a surface, like distance, angle, or area, change when the surface is deformed. Euler discovered a quantity, the Euler characteristic, which remains unchanged. The formula of Gauss-Bonnet, a landmark result of mathematics, relates Euler characteristic with geometry. In the talk, I will present ideas of Descartes, Euler, and Gauss related to this formula.

## Hirzebruch colloquium talk by Walter Neumann

## Hirzebruch Colloqium

15:00-16:00

tba

tba

16:00-16:30

Special tea

16:30-17:30

tba

tba

## tba

## Topological Twists of Factorization Algebras

The idea of topologically twisting a supersymmetric field theory was introduced in the physics literature in order to generate interesting new examples of topological field theories. The idea is very general, but systematically realising the examples it produces is not always possible using mathematical models for topological field theory (such as Atiyah-Segal's functorial field theory, or the theory of E_n-algebras). In this talk I'll explain what it means to twist a supersymmetric field theory in the factorization algebra framework devel