Let \(T : X \to X\) be a bounded linear operator on a complex Banach space \(X\). Prove that \(\sigma (T)\) lies in the complex plane disk: \(\{\lambda \in \mathbb {C} \mid |\lambda | \le \|T\|\}\).
Question
Math 6710 • Applied Linear Operators and Spectral Methods
Spring 2021 • Question 5