Non-Analytic Functional Calculi in Several Variables.
Non-analytic local functional calculus
Non-analytic local spectral properties in several variables
Non-holomorphic functional calculus for commuting operators with real spectrum
We consider -tuples of commuting operators on a Banach space with real spectra. The holomorphic functional calculus for is extended to algebras of ultra-differentiable functions on , depending on the growth of , , when . In the non-quasi-analytic case we use the usual Fourier transform, whereas for the quasi-analytic case we introduce a variant of the FBI transform, adapted to ultradifferentiable classes.
Non-isometric functional calculus for pairs of commuting contractions.
Notes on the Taylor joint spectrum of commuting operators
N-th roots of a non-negative operator: conditions for uniqueness.
Null spaces and ranges of polynomials of operators.
We give an elementary proof of the fact that given two polynomials P, Q without common zeros and a linear operator A, the operators P(A) and Q(A) verify some properties equivalent to the pair (P(A),Q(A)) being non-singular in the sense of J.L. Taylor. From these properties we derive expressions for the range and null space of P(A) and spectral mapping theorems for polynomials fo continuous (or closed) operators in Banach spaces.