Un problema ai limiti per un'equazione astratta del secondo ordine
The following results are proved: (i) if , and is a sectorial operator, then the set is bounded; (ii) the same set of operators is R-bounded if is R-sectorial.
We give a concise exposition of the basic theory of functional calculus for N-tuples of sectorial or bisectorial operators, with respect to operator-valued functions; moreover we restate and prove in our setting a result of N. Kalton and L. Weis about the boundedness of the operator when f is an R-bounded operator-valued holomorphic function.
Let be the realization () of a differential operator on with general boundary conditions (). Here is a homogeneous polynomial of order in complex variables that satisfies a suitable ellipticity condition, and for is a homogeneous polynomial of order ; it is assumed that the usual complementing condition is satisfied. We prove that is a sectorial operator with a bounded functional calculus.
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