Zero-two law for cosine families

Felix Schwenninger, Hans Zwart

For ${\left(C(t)\right)}_{t\ge 0}$ being a strongly continuous cosine family on a Banach space, we show that the estimate ${\mathrm{limsup}}_{t\to 0^{+}}\Vert C(t)-I\Vert <2$ implies that $C(t)$…