Lehrstuhl Prof. Dr. Gerhard Röhrle

Wissenschaftliche Arbeitsgebiete


  • Algebraische Lie Theorie
  • Algebraische Gruppen
  • Endliche Gruppen vom Lie Typ
  • Darstellungstheorie
  • Hyperebenenarrangements

2 Vorträg im Oberseminar Arrangements

Montag, den 22.1.18, 14:15 Uhr, Wasserstrasse 221, Raum 4/20

Vortragender: Prof. Daniel C. Cohen (Louisiana State University, Baton Rouge, LA, USA)

Title: Pure braid groups and direct products of free groups

I'll discuss some properties and invariants of fundamental groups of complements of arrangements, largely in the context of the above classes. By the end of the talk, I should be able to pose a question we might discuss during the week.

Mittwoch, den 24.1.18, 14:15 Uhr, Wasserstrasse 221, Raum 4/20

Vortragender: Prof. Daniel C. Cohen (Louisiana State University, Baton Rouge, LA, USA)

Title: Topological complexity of surfaces and their configuration spaces

Topological complexity is a numerical homotopy-type invariant introduced by M. Farber about 15 years ago, motivated by the motion planning problem from robotics. For a given space, this invariant provides a measure of the complexity of navigation in the space. Computing this invariant is sometimes easy, sometimes hard. I'll attempt to illustrate this, with surfaces and their configuration spaces.

Spring School on Complete Reducibility

In April 2018 we will host a spring school, aimed at introducing graduate students and junior researchers to the notion of G-complete reducibility, featuring a lecture series by Professor Ben Martin (Aberdeen), and a number of additional lectures.


Alexander von Humboldt Fellowship awarded to Dr Litterick


We are very pleased to announce that Dr Alastair Litterick has been awarded a competitive two-year Alexander von Humboldt Fellowship for Postdoctoral Researchers, hosted by Professors Christopher Voll (Bielefeld University) and Gerhard Röhrle (Ruhr-University Bochum), with a research topic of 'Subgroup structure and generation properties in reductive groups'. Reductive groups are an important class of mathematical objects which lie at the intersection between algebra and geometry. Because of their multi-faceted nature, they are important throughout mathematics and beyond, arising naturally, for instance, in branches of theoretical physics such as string theory.

Dr Litterick's research focuses on algebraic properties of these groups. Although the groups themselves are easy to describe, several aspects of their subgroup structure remain mysterious. In particular, he is concerned with understanding subgroups which are themselves reductive group, and with subgroups containing elements of specified forms. Current approaches to these problems involve many diverse areas of pure mathematics, including algebraic geometry, computational algebra, geometric group theory, geometric invariant theory, Lie theory, cohomology theory, representation theory, and still more. Working in the diverse groups of Professors Voll and Röhrle, Dr Litterick intends to pursue all of these avenues towards the solutions of these problems.

Visiting International Professor Fellowship


Professor Benjamin Martin from the University of Aberdeen has been awarded a VIP Professorship by the RUB-Research School.

Professor Martin is one of the worlds experts in algebraic groups, representation varieties and representation growth,and related fields such as representation theory and the theory of buildings. More specifically, he is a world leader in the theory of complete reducibility for algebraic groups and geometric invariant theory associated with the action of reductive groups on affine varieties.

Over the course of the next two years he will be visting the department of mathematics and will contribute to the postgraduate education within the chair of Professor G. Röhrle

For the RUB-Research school and the VIP-Programme, see also here


"Research Explorer Ruhr"


We are delighted to announce that the application of Dr. Tomohiro Uchiyama (National Taiwan University, National Center for Theoretical Sciences) within the Research Explorer Ruhr programme of the RUB Research School have been successful. The researcher will be visiting the Lehrstuhl in the period June 19 - 30. During his visit he will be able to explore possible research interactions and collaboration possibilities within our research group. At the same time the Research school offers an accompanying programme which will provide information about various possibilities for funding a postdoc position, so that he potentially might return to the Ruhr-University as Postdoc.

For more information on the Research Explorer Ruhr programme of the RUB, see here.



Tilman Möller, Gerhard Röhrle

Bei der Akademischen Jahresfeier 2016 wurde Herr Tilman Möller mit dem RUB-Preis für seine Masterarbeit "Induktiv faktorisierte Arrangements und deren Abgeschlossenheit unter Lokalisierung" ausgezeichnet.

DFG-Grant awarded to Professor Röhrle


Inductive freeness and rank generating functions of arrangements of ideal type: two conjectures of Sommers and Tymoczko revisited

The grant provides financial support for a research post for three years. The topic of the research project focuses on the interplay on the one hand of Lie theoretic and combinatorial aspects of root systems and on the other on geometric and algebraic properties of a particular class of real hyperplane arrangements stemming from certain subsets of the set of positive roots of a reduced root system.


IRB Research Grant

Anne Schauenburg obtained one of the competitive IRB research grants from the Ruhr University Research School PLUS, funded by Germany’s Excellence Initiative [DFG GSC 98/3]. The IRB targets doctoral researchers in the first year who want to enrich their doctorate by several international activities. It is planned that Ms Schauenburg will use her grant to intensify international collaboration and networking with researchers working in the area of her doctorate via research stays and conference participation.


Archiv der laufenden Ankündigungen



Tel.: +49(0)234-32-28304
Fax: +49(0)234-32-14025

E-Mail: gerhard.roehrle@ruhr-uni-bochum.de