Algebras of Complete Hörmander Vector Fields, and Lie-Group Construction


  • Andrea Bonfiglioli University of Bologna



Hörmander vector fields, Campbell-Baker-Hausdorff-Dynkin Theorem, Third Theorem of Lie, Carnot-Carathéodory metric, Completeness of vector fields


The aim of this note is to characterize the Lie algebras g of the analytic vector fields in RN which coincide with the Lie algebras of the (analytic) Lie groups defined on RN (with its usual differentiable structure). We show that such a characterization amounts to asking that: (i) g is N-dimensional; (ii) g admits a set of Lie generators which are complete vector fields; (iii) g satisfies Hörmander’s rank condition. These conditions are necessary, sufficient and mutually independent. Our approach is constructive, in that for any such g we show how to construct a Lie group G = (RN, *) whose Lie algebra is g. We do not make use of Lie’s Third Theorem, but we only exploit the Campbell-Baker-Hausdorff-Dynkin Theorem for ODE’s.


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How to Cite

Bonfiglioli, A. (2014). Algebras of Complete Hörmander Vector Fields, and Lie-Group Construction. Bruno Pini Mathematical Analysis Seminar, 5(1), 15–30.