Uniqueness results for the Dirichlet problem for higher order elliptic equations in polyhedral angles (Q481620)

The authors consider the Dirichlet boundary value problem for higher order elliptic equations in divergence form with discontinuous coefficients in polyhedral angles. Precisely, \[ \begin{cases} \sum_{|\alpha|=|\beta|=m} D^\alpha(a_{\alpha\beta}(x)D^\beta u(x))=0 & \text{ in } \mathbb R^n_l\cr \partial^ju(x)/\partial\nu^j =0 & \text{ on } \partial \mathbb R^n_l, j=0,\ldots, m-1\,. \end{cases} \] Some uniqueness results are obtained.