1. The Rouché Theorem for Fredholm functions: An enhanced version.
- Author
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Bart, H., Ehrhardt, T., and Silbermann, B.
- Subjects
- *
OPERATOR functions , *FREDHOLM operators - Abstract
The classical Rouché Theorem from complex function theory has been generalized to a result involving Fredholm operator valued functions (see [9] and [6]). The setting in question is (generally) a non-commutative one, so actually there are two versions of the generalization. In this paper, a unifying enhanced variant is presented involving the notion of the spectral radius. Its proof is based on a maximum principle for the spectral radius. An example is given showing that the enhanced Rouché Theorem presented here is a genuine improvement over the earlier version of the result. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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