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Katrin Fässler


I am an associate professor at the University of Jyväskylä (Finland). From September 2019 to July 2025, I work as a research fellow of the Academy of Finland. Previously, I was an SNSF Ambizione fellow at the University of Fribourg (Switzerland) and I held postdoctoral positions at the Universities of Helsinki, Bern, and Jyväskylä. My interests lie in mapping theory, geometric measure theory and topics inbetween.



Mapping theory and geometric measure theory


My research is concerned with mappings that distort distances in a controllable fashion: Lipschitz, quasiconformal, and quasiregular maps.


The sub-Riemannian Heisenberg group is a prototypical example of the kind of spaces I am interested in. While topologically 3-dimensional, it differs significantly from Euclidean space from a metric point of view. The sub-Riemannian structure imposes for instance certain constraints on metric Lipschitz maps from Euclidean space to the Heisenberg group. A large part of classical geometric measure theory is concerned with the study of Lipschitz maps and rectifiable sets. In the Heisenberg group, the counterpart for these concepts are "intrinsic" (rather than "metric") Lipschitz maps and intrinsically rectifiable sets.

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2008 - 2011

University of Bern (Switzerland)

PhD in Mathematics


  • Finnish Academy Research Fellowship Project Singular integrals, harmonic functions, and boundary regularity in Heisenberg groups, 2019-2025, Grant Nos. 321696, 328846, 352649

  • Swiss National Science Foundation "Ambizione" Fellowship Intrinsic rectifiability and mapping theory on the Heisenberg group, 2016-2019, Grant No. 161299

  • Finnish Academy Postdoctoral Project Sub-Riemannian manifolds from a quasiconformal viewpoint, 09/2015-08/2016, Grant No. 285159

  • Swiss National Science Foundation Fellowship for prospective researchers Dimension correlation for projections in non-Euclidean geometries, 02/2012-01/2013, Grant No. 141456

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