Abstract
For an unbounded operator S on a Banach space the existence of invariant subspaces corresponding to its spectrum in the left and right half-plane is proved. The general assumption on S is the uniform boundedness of the resolvent along the imaginary axis. The projections associated with the invariant subspaces are bounded if S is strictly dichotomous, but may be unbounded in general. Explicit formulas for these projections in terms of resolvent integrals are derived and used to obtain perturbation theorems for dichotomy. All results apply, with certain simplifications, to bisectorial operators.
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This work was partially supported by a research grant of the “Fachgruppe Mathematik und Informatik” at the University of Wuppertal and FAPA No. PI160322022 of the Facultad de las Ciencias of the Universidad de Los Andes.
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Winklmeier, M., Wyss, C. On the Spectral Decomposition of Dichotomous and Bisectorial Operators. Integr. Equ. Oper. Theory 82, 119–150 (2015). https://doi.org/10.1007/s00020-015-2218-5
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DOI: https://doi.org/10.1007/s00020-015-2218-5