# Remarks on the Operator-Norm Convergence of the Trotter Product Formula

Research paper by Hagen Neidhardt, Artur Stephan, Valentin A. Zagrebnov

Indexed on: 12 Mar '18Published on: 12 Mar '18Published in: Integral Equations and Operator Theory

#### Abstract

We revise the operator-norm convergence of the Trotter product formula for a pair $$\{A,B\}$$ of generators of semigroups on a Banach space. Operator-norm convergence holds true if the dominating operator A generates a holomorphic contraction semigroup and B is a A-infinitesimally small generator of a contraction semigroup, in particular, if B is a bounded operator. Inspired by studies of evolution semigroups it is shown in the present paper that the operator-norm convergence generally fails even for bounded operators B if A is not a holomorphic generator. Moreover, it is shown that operator norm convergence of the Trotter product formula can be arbitrary slow.