Criteria for algebraic operators to be unitary
Zenon Jan Jabłoński, Il Bong Jung, Jan Stochel · arXiv (Cornell University) · 2024
Criteria for an algebraic operator $T$ on a complex Hilbert space $\mathcal{H}$ to be unitary are established. The main one is written in terms of the convergence of sequences of the form $\{\|T^nh\|\}_{n=0}^{\infty}$ with $h\in \mathcal{H}$. Related questions are also discussed.