# Members & Guests

## Dr. Rudolf Zeidler

Westfälischen Wilhelms-Universität Münster

E-mail: rudolf.zeidler(at)uni-muenster.de
Homepage: https://www.rzeidler.eu/

## Project

78Duality and the coarse assembly map II

## Publications within SPP2026

Let $$\mathcal{E}$$ be an asymptotically Euclidean end in an otherwise arbitrary complete and connected Riemannian spin manifold $$(M,g)$$. We show that if $$\mathcal{E}$$ has negative ADM-mass, then there exists a constant $$R > 0$$, depending only on $$\mathcal{E}$$, such that $$M$$ must become incomplete or have a point of negative scalar curvature in the $$R$$-neighborhood around $$\mathcal{E}$$ in $$M$$. This gives a quantitative answer to Schoen and Yau's question on the positive mass theorem with arbitrary ends for spin manifolds. Similar results have recently been obtained by Lesourd, Unger and Yau without the spin condition in dimensions $$\leq 7$$ assuming Schwarzschild asymptotics on the end $$\mathcal{E}$$. We also derive explicit quantitative distance estimates in case the scalar curvature is uniformly positive in some region of the chosen end $$\mathcal{E}$$. Here we obtain refined constants reminiscent of Gromov's metric inequalities with scalar curvature.

We use the Dirac operator technique to establish sharp distance estimates for compact spin manifolds under lower bounds on the scalar curvature in the interior and on the mean curvature of the boundary. In the situations we consider, we thereby give refined answers to questions on metric inequalities recently proposed by Gromov. This includes optimal estimates for Riemannian bands and for the long neck problem. In the case of bands over manifolds of non-vanishing $$\widehat{\mathrm{A}}$$-genus, we establish a rigidity result stating that any band attaining the predicted upper bound is isometric to a particular warped product over some spin manifold admitting a parallel spinor. Furthermore, we establish scalar- and mean curvature extremality results for certain log-concave warped products. The latter includes annuli in all simply-connected space forms. On a technical level, our proofs are based on new spectral estimates for the Dirac operator augmented by a Lipschitz potential together with local boundary conditions.