We observe that the diameter of small (in a locally uniform sense) balls in C^{1,1} sub-Riemannian manifolds equals twice the radius. We also prove that, when the regularity of the structure is further lowered to C^0, the diameter is arbitrarily close to twice the radius. Both results hold independently of the bracket-generating condition.

A note on the diameter of small sub-Riemannian balls

Marco Di Marco;Gianluca Somma;Davide Vittone
2026

Abstract

We observe that the diameter of small (in a locally uniform sense) balls in C^{1,1} sub-Riemannian manifolds equals twice the radius. We also prove that, when the regularity of the structure is further lowered to C^0, the diameter is arbitrarily close to twice the radius. Both results hold independently of the bracket-generating condition.
2026
   Challenges and Breakthroughs in the Mathematics of Plasmas
   Swiss National Science Foundation (SNSF)

   Variational, Geometric, and Analytic Perspectives on Regularity
   INdAM-GNAMPA
   CUP:E53C25002010001

   Variational Aspects of Currents & other results in Geometric Measure Theory
   VAC&GMT
   INdAM

   Geometric Measure Theory: Structure of Singular Measures, Regularity Theory and Applications in the Calculus of Variations
   MIUR
   CUP:E53D23005860006
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11577/3598158
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