We consider manifolds with conic singularities that are isometric to Rn outside a compact set. Under natural geometric assumptions on the cone points, we prove the existence of a logarithmic resonance-free region for the cut-off resolvent. The estimate also applies to the exterior domains of non-trapping polygons via a
doubling process.
The proof of the resolvent estimate relies on the propagation of singularities theorems of Melrose and the second author [23]
to establish a “very weak” Huygens’ principle, which may be of independent interest.
As applications of the estimate, we obtain a exponential local energy decay and a resonance wave expansion in odd dimensions,
as well as a lossless local smoothing estimate for the Schr¨odinger equation.