Gregory Verchota
Abstract: A family of linear homogeneous 4th order elliptic differential operators $L$ with real constant coefficients, and bounded nonsmooth convex domains $\Omega$ are constructed in $\mathbb{R}^6$ so that the $L$ have no constant coefficient coercive integro-differential quadratic forms over the Sobolev spaces $W^{2,2}(\Omega)$.
Journal: J. Eur. Math. Soc. (JEMS) 16 (2014), no. 10, 2165–2210.
DOI: 10.4171/JEMS/485