Integral Equations and Operator Theory

, Volume 62, Issue 4, pp 489–515 | Cite as

\(\mathcal {PT}\) -Symmetric Waveguides

  • Denis Borisov
  • David Krejčiřík


We introduce a planar waveguide of constant width with non-Hermitian \(\mathcal {PT}\) -symmetric Robin boundary conditions. We study the spectrum of this system in the regime when the boundary coupling function is a compactly supported perturbation of a homogeneous coupling. We prove that the essential spectrum is positive and independent of such perturbation, and that the residual spectrum is empty. Assuming that the perturbation is small in the supremum norm, we show that it gives rise to real weakly-coupled eigenvalues converging to the threshold of the essential spectrum. We derive sufficient conditions for these eigenvalues to exist or to be absent. Moreover, we construct the leading terms of the asymptotic expansions of these eigenvalues and the associated eigenfunctions.

Mathematics Subject Classification (2000).

35P15 35J05 47B44 47B99 


Non-self-adjointness J-self-adjointness waveguides \(\mathcal {PT}\) -symmetry Robin boundary conditions Robin Laplacian eigenvalue and eigenfunction asymptotics essential spectrum reality of the spectrum 


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Copyright information

© Birkhaueser 2008

Authors and Affiliations

  1. 1.Department of Physics and MathematicsBashkir State Pedagogical UniversityUfaRussia
  2. 2.Department of Theoretical PhysicsNuclear Physics Institute Academy of SciencesŘežCzech Republic

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