Über approximative derivierte Zahlen
Über ein konstruktives Analogon eines Satzes von K. M. Garg über Ableitungszahlen
Ultrarigid tangents of sub-Riemannian nilpotent groups
We show that the tangent cone at the identity is not a complete quasiconformal invariant for sub-Riemannian nilpotent groups. Namely, we show that there exists a nilpotent Lie group equipped with left invariant sub-Riemannian metric that is not locally quasiconformally equivalent to its tangent cone at the identity. In particular, such spaces are not locally bi-Lipschitz homeomorphic. The result is based on the study of Carnot groups that are rigid in the sense that their only quasiconformal maps...