Riesz basis property of root vectors of nonselfadjoint operators generated by radial damped wave equations (Q5954437)

The main result in this paper is that the root vectors (eigenvectors and associated vector) to some nonselfadjoint operators arising in the study of radial (in the space \(\mathbb{R}^3\)) damped wave equations have the Riesz basis property in the associated energy spaces. This provides a new nontrivial example of operators having the spectral property. Applications to exact controllability, closed loop control and periodic control are also given.