Abstract
In earlier papers we introduced and studied the notion of fractal operator that maps a continuous scalar valued function on a compact interval in \({\mathbb {R}}\) to its fractal (self-referential) analogue. Further, it has been observed that by perturbing known Schauder bases via the bijective bicontinuous fractal operator, Schauder bases consisting of self-referential functions can be constructed for standard function spaces. Motivated by the theory and applications of the fractal operator, in this note we propose a new kind of perturbation of linear operators. We consider a pair of linear operators L and T on a Banach space X such that
for all \(x \in X\) and some \(k >0\). We establish that the property of being bounded below and that of having a closed range are stable under the perturbation considered herein. As an immediate application, it is deduced that a given Schauder basis in X can be transformed to Schauder sequences. Perturbation of linear operators via an equation of the form
is also alluded and its application in constructing new Schauder bases from a given one is considered.
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Navascués, M.A., Viswanathan, P. Perturbation of linear operators on Banach spaces: some applications to Schauder bases and frames. Aequat. Math. 94, 13–36 (2020). https://doi.org/10.1007/s00010-019-00681-6
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DOI: https://doi.org/10.1007/s00010-019-00681-6