“…Inspired by the norm used in the theory of operator semigroups (see, e.g. the proof of Theorem 5.2 in Chapter 1 of [
60]), we introduce a new semi‐norm on
, which will lead to the semi‐contractivity property [
58, 59] of the matrix exponential of the negative Laplacian matrix.
Lemma Let be an arbitrary norm on , and let .…”