Inserted: 11 apr 2003
Last Updated: 12 dec 2003
Journal: Proc. Amer. Math. Soc.
We study the problem of accessibility of boundary points for domains in the sub--Riemannian setting of the first Heisenberg group. A sufficient condition for accessibility is given. It is a Dini--type continuity condition for the horizontal gradient of the defining function. The sharpness of this condition is shown by examples.
Keywords: Heisenberg group, Accessibility , Dini condition