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Harmonic maps into Euclidean buildings and non-Archimedean superrigidity

Christine Breiner, Ben K Dees and Chikako Mese

Geometry & Topology 30 (2026) 2251–2296
Abstract

We prove that harmonic maps into Euclidean buildings, which include -buildings, have singular sets of Hausdorff codimension 2, extending the locally finite regularity result of Gromov and Schoen. As an application, we prove superrigidity for algebraic groups over fields with non-Archimedean valuation, thereby generalizing the rank-1 p-adic superrigidity results of Gromov and Schoen and casting the Bader–Furman generalization of Margulis’ higher-rank superrigidity result in a geometric setting. We also prove an existence theorem for a pluriharmonic map from a Kähler manifold to a Euclidean building.

Keywords
harmonic maps, superrigidity, Euclidean buildings
Mathematical Subject Classification
Primary: 53C43, 58E20
Secondary: 22E40, 22E50
References
Publication
Received: 30 August 2024
Revised: 2 February 2026
Accepted: 11 March 2026
Published: 31 July 2026
Proposed: Tobias H Colding
Seconded: David Fisher, Bruce Kleiner
Authors
Christine Breiner
Department of Mathematics
Brown University
Providence, RI
United States
Ben K Dees
Department of Mathematics
Brown University
Providence, RI
United States
Chikako Mese
Department of Mathematics
Johns Hopkins University
Baltimore, MD
United States

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