Let X be a connected Riemannian manifold such that the resolvent of the
free Laplacian (\Delta-z)^{-1}, z\in\C\setminus\R^{+}, has a meromorphic
continuation through R+. The poles of this continuation are called
resonances. When X has some symmetries, we construct complex-valued
potentials, V, such that the resolvent of Δ+V, which has also a
meromorphic continuation, has the same resonances with multiplicities as the
free Laplacian.Comment: 32 page