1 citations · 2 across the 4 of their papers we have counts for
4 papers
A short proof of the zero-two law for cosine functions
Jean Esterle
Let $(C(t))\in\mathbb{R}}$ be a cosine function in a unital Banach algebra. We give a simple proof of the fact that if lim sup$\_{t\to 0}\vert C(t)-1\_A\vert\textless{}2,$ then $li…
A zero-sqrt(5)/ 2 law for cosine families
Jean Esterle
Let and let be the largest constant such that $sup\vert cos(na)-cos(nb)\vert \textless{} k(a)$ for implies that We show that if a…
Lower estimates near the origin for functional calculus on operator semigroups
I. Chalendar, J. Esterle, J. R. Partington
This paper provides sharp lower estimates near the origin for the functional calculus of a generator of an operator semigroup defined on the (strictly) positive real l…
Bounded cosine functions close to continuous scalar bounded cosine functions
Jean Esterle
Let be a cosine function in a unital Banach algebra. We show that if $sup\_{t\in R}\Vert C(t)-cos(t)\Vert \textless{} 2$ for some continuous scalar bounded cosi…