$H^\infty$-calculus for the sum of non-commuting operators
$H^\infty$-calculus for the sum of non-commuting operators
A recent result of Kalton and Weis is extended to the case of non-commuting operators, employing the commutator condition of Labbas and Terreni, or of Da Prato and Grisvard. Under appropriate assumptions it is shown that the sum of two non-commuting operators admits an $\mathcal H^\infty$-calculus. The main results are …