Stable broken H1 and H(div) polynomial extensions

Main results: H1-stable polynomial extension on a tetrahedron; H(div)-stable polynomial extension on a tetrahedron; stable broken H1 polynomial extension on a patch of thetrahedra; stable broken H(div) polynomial extension on a patch of thetrahedra; polynomial-degree-robust efficiency of H1-nonconforming methods; polynomial-degree-robust efficiency of H(div)-nonconforming methods. Details: paper (preprint) with Alexandre Ern…