## 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

#### A small closed convex projective 4-manifold via Dehn filling

Gye-Seon Lee, Ludovic Marquis, Stefano Riolo

In order to obtain a closed orientable convex projective four-manifold with small positive Euler characteristic, we build an explicit example of...

#### 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...

#### Currents, systoles, and compactifications of character varieties

Marc Burger, Alessandra Iozzi, Anne Parreau, Beatrice Pozzetti

We study the Thurston–Parreau boundary both of the Hitchinand of the maximal character varieties and determine therein an open setof discontinuity for...

## Latest Blog posts

**A Prime Breakthrough**It seems that at the beginning of this year a major breakthrough on prime numbers was achieved. I learned about it from this blog: link. Let me summarize the result quickly for you if you don’t want to read the other blog post. Almost a hundred years ago Jensen and Pólya proved that the Riemannian … Continue reading "A Prime Breakthrough"

**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"