7 papers
Néron blowups and low-degree cohomological applications
Arnaud Mayeux, Timo Richarz, Matthieu Romagny
We define dilatations of general schemes and study their basic properties. Dilatations of group schemes are -- in favorable cases -- again group schemes, called Néron blowups. We g…
Normality and Cohen-Macaulayness of parahoric local models
Thomas J. Haines, Timo Richarz
We study the singularities of integral models of Shimura varieties and moduli stacks of shtukas with parahoric level structure. More generally our results apply to the Pappas-Zhu a…
The intersection motive of the moduli stack of shtukas
Timo Richarz, Jakob Scholbach
For a split reductive group G over a finite field, we show that the intersection (cohomology) motive of the moduli stack of iterated G-shtukas with bounded modification and level s…
Smoothness of Schubert varieties in twisted affine Grassmannians
Thomas J. Haines, Timo Richarz
We give a complete list of smooth and rationally smooth normalized Schubert varieties in the twisted affine Grassmannian associated with a tamely ramified group and a special verte…
The Test Function Conjecture for Local Models of Weil-restricted groups
Thomas J. Haines, Timo Richarz
We prove the test function conjecture of Kottwitz and the first named author for local models of Shimura varieties with parahoric level structure attached to Weil-restricted groups…
A new approach to the geometric Satake equivalence
Timo Richarz
I give another proof of the geometric Satake equivalence from Mirkovic-Vilonen over a separably closed field. Using Galois descent, I obtain a canonical construction of the Galois…