Extreme localisation of eigenfunctions to one-dimensional high-contrast periodic problems with a defect

Cherdantsev, Mikhail ORCID: https://orcid.org/0000-0002-5175-5767, Cherednichenko, Kirill and Cooper, Shane 2018. Extreme localisation of eigenfunctions to one-dimensional high-contrast periodic problems with a defect. Siam Journal on Mathematical Analysis 50 (6) , pp. 5825-5856. 10.1137/17M112261X

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Abstract

Following a number of recent studies of resolvent and spectral convergence of nonuniformly elliptic families of differential operators describing the behavior of periodic composite media with high contrast, we study the corresponding one-dimensional version that includes a “defect”: an inclusion of fixed size with a given set of material parameters. It is known that the spectrum of the purely periodic case without the defect and its limit, as the period $\varepsilon$ goes to zero, has a band-gap structure. We consider a sequence of eigenvalues $\lambda_\varepsilon$ that are induced by the defect and converge to a point $\lambda_0$ located in a gap of the limit spectrum for the periodic case. We show that the corresponding eigenfunctions are “extremely” localized to the defect, in the sense that the localization exponent behaves as $\exp(-\nu/\varepsilon),$ $\nu>0,$ which has not been observed in the existing literature. In two- and three-dimensional configurations, whose one-dimensional cross sections are described by the setting considered, this implies the existence of propagating waves that are localized to a vicinity of the defect. We also show that the unperturbed operators are norm-resolvent close to a degenerate operator on the real axis, which is described explicitly.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Mathematics
ISSN:	1095-7154
Date of First Compliant Deposit:	17 September 2018
Date of Acceptance:	22 August 2018
Last Modified:	06 May 2023 03:19
URI:	https://orca.cardiff.ac.uk/id/eprint/114999

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