Non-Elliptic Quadratic $\mathcal{P}\mathcal{T}$-Symmetric Operators and Similarity to Self-Adjoint Operators

Abstract

We prove a similarity result for non-self-adjoint non-elliptic quadratic $\mathcal{P}\mathcal{T}$-symmetric operators with real spectrum satisfying a dynamical averaging condition. In particular, we show that such an operator is weakly similar to a self-adjoint operator precisely when the fundamental matrix of the associated quadratic form is diagonalizable.

11 pages