Fässler, Katrin Orponen, Tuomas 2020 A theorem of Dorronsoro from the 1980s quantifies the fact that real‐valued Sobolev functions on Euclidean spaces can be approximated by affine functions almost everywhere, and at all sufficiently small scales. We prove a variant of Dorronsoro's theorem in Heisenberg groups: functions in horizontal Sobolev spaces can be approximated by affine functions which are independent of the last variable. As an application, we deduce new proofs for certain vertical versus horizontal Poincaré inequalities for real‐valued functions on the Heisenberg group, originally due to Austin–Naor–Tessera and Lafforgue–Naor. application/pdf https://sonar.ch/global/documents/308722 https://sonar.ch/documents/308722/files/fae_dth.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1112/blms.12341 info:eu-repo/semantics/openAccess License undefined Bulletin of the London Mathematical Society. - 2020, vol. 52, no. 3, p. 472–488 info:eu-repo/classification/udc/51 Dorronsoro’s theorem in Heisenberg groups http://purl.org/coar/resource_type/c_6501