On a conformal manifold with
boundary, we construct conformally invariant local boundary conditions B for the
conformally invariant power of the Laplacian □k , with the property that (□k,B)
is formally self-adjoint. These boundary problems are used to construct
conformally invariant non-local operators on the boundary Σ, generalizing the
conformal Dirichlet-to-Robin operator, with principal parts which are odd
powers h (not necessarily positive) of (−ΔΣ)1∕2, where ΔΣ is the boundary
Laplace operator. The constructions use tools from a conformally invariant
calculus.