Abstract. We prove comparison theorems for the H∞-calculus that allow to transfer the property of having a bounded H∞-calculus from one sectorial operator to another. The basic technical ingredient are suitable square function estimates. These comparison results provide a new approach to perturbation theorems for the H∞-calculus in a variety of situations suitable for applications. Our square f...

Fractional calculus is a branch of mathematics that studies the use fractional operators. The evolution computing allowed its application in many areas, including control theory. operators are known to well describe memory phenomena, favorable characteristic for control. Another benefit order these adds more tunable parameters controller, allowing greater flexibility and possibility improving p...