Address: University of Bergen, Department of Mathematics, P.O. Box 7803, 5020 Bergen, Norway
E-mail: erlend.grong@uib.no
Abstract: These notes give an introduction to the equivalence problem of sub-Riemannian manifolds. We first introduce preliminaries in terms of connections, frame bundles and sub-Riemannian geometry. Then we arrive to the main aim of these notes, which is to give the description of the canonical grading and connection existing on sub-Riemann manifolds with constant symbol. These structures are exactly what is needed in order to determine if two manifolds are isometric. We give three concrete examples, which are Engel (2,3,4)-manifolds, contact manifolds and Cartan (2,3,5)-manifolds. These notes are an edited version of a lecture series given at the 42nd Winter school: Geometry and Physics, Srní, Czech Republic, mostly based on [8] and other earlier work. However, the work on Engel (2,3,4)-manifolds is original research, and illustrate the important special case were our model has the minimal set of isometries.
AMSclassification: primary 53C17; secondary 58A15.
Keywords: sub-Riemannian geometry, equivalence problem, frame bundle, Cartan connection, flatness theorem.
DOI: 10.5817/AM2022-5-295