## Welcome to SPP 2026

This is the platform of a coordinated research programme in mathematics, funded by the German Research Foundation (DFG). It comprises 33 research projects in the fields of differential geometry, geometric topology, and global analysis. More than 80 researchers from doctoral to professorial level and based at more than 20 German and Swiss universities are represented in this programme.

### Call for proposals 2020-2023

The call for proposals for the second funding period 2020-2023 has been released by the DFG.

## Next Activities

## Latest publications

#### Anti-de Sitter strictly GHC-regular groups which are not lattices

Gye-Seon Lee, Ludovic Marquis

For d = 4, 5, 6, 7, 8, we exhibit examples of \(\mathrm{AdS}^{d,1}\) strictly GHC-regular groups which are not quasi-isometric to the hyperbolic space...

#### Boundary value problems for general first-order elliptic differential operators

Christian Bär, Lashi Bandara

We study boundary value problems for first-order elliptic differential operators on manifolds with compact boundary. The adapted boundary operator...

#### Geometry and topology of the Kerr photon region in the phase space

Carla Cederbaum, Sophia Jahns

We study the set of trapped photons of a subcritical (a<M) Kerr spacetime as a subset of the phase space. First, we present an explicit proof that the...

#### Between buildings and free factor complexes: A Cohen-Macaulay complex for Out(RAAGs)

Benjamin Brück

For every finite graph Γ, we define a simplicial complex associated to the outer automorphism group of the RAAG A_Γ. These complexes are defined as...

## Latest Blog posts

**Laplace operator and covering spaces**Let M be a closed Riemannian manifold and denote by X its universal covering space equipped with the pulled back Riemannian metric. There is an intimate relation between the Laplace operator on X and the fundamental group of M. One example of this is the result of Brooks from 1981: the fundamental group of M … Continue reading "Laplace operator and covering spaces"

**Lindelöf hypothesis**Today I stumbled across a news article ( link ) written about someone (actually, Athanassios Fokas – a known mathematician) having announced progress on the Lindelöf hypothesis ( wikipedia ). The Lindelöf hypothesis is related to the Riemannian hypothesis and actually also follows from it – progress on the Lindelöf hypothesis would also mean progress … Continue reading "Lindelöf hypothesis"

**Girls and boys performing in STEM fields**This is actually already old news (it is from September 2018), but since then it was on my list of things to blog about and only now I found the time to actually do it. There was a meta-study published in Nature Communications (doi:10.1038/s41467-018-06292-0) about the performance of girls and boys in STEM fields. I … Continue reading "Girls and boys performing in STEM fields"