Sebastian Boldt (Chemnitz) will speak in the geometry seminar at 2pm on Monday 10th February, in the Salle des Profs (9th floor of building NO). Sebastian’s title is “The normal injectivity radius of a hypersurface” and his abstract is below.
We present a pointwise lower estimate of the normal radius of an embedded hypersurface in an arbitrary Riemannian manifold. The key ingredient to this result is a new two-sided radial angle comparison theorem. As an application we construct metrics of bounded geometry on manifolds with boundary.