Abstract <p> In this paper, we consider the Bloch eigenvalues and spectrum of the non-self-adjoint differential operator <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10688_2025_1171_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="16" /> </InlineMediaObject> <EquationSource Format="TEX">\(L\)</EquationSource> </InlineEquation> generated by the differential expression of odd order <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10688_2025_1171_Article_IEq3.gif" Format="GIF" Height="10" Rendition="HTML" Resolution="72" Type="Linedraw" Width="14" /> </InlineMediaObject> <EquationSource Format="TEX">\(n\)</EquationSource> </InlineEquation> with periodic <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10688_2025_1171_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="27" /> </InlineMediaObject> <EquationSource Format="TEX">\(\mathcal{PT}\)</EquationSource> </InlineEquation>-symmetric coefficients, where <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10688_2025_1171_Article_IEq5.gif" Format="GIF" Height="13" Rendition="HTML" Resolution="72" Type="Linedraw" Width="42" /> </InlineMediaObject> <EquationSource Format="TEX">\(n&gt;1\)</EquationSource> </InlineEquation>. We study the localizations of the Bloch eigenvalues and the structure of the spectrum. Moreover, we find conditions on the norm of the coefficients under which the spectrum of <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="10688_2025_1171_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="16" /> </InlineMediaObject> <EquationSource Format="TEX">\(L\)</EquationSource> </InlineEquation> is purely real and coincides with the real line. </p>

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On the Spectrum of the Differential Operators of Odd Order with \(\mathcal{PT}\)-Symmetric Coefficients

  • Oktay Veliev

摘要

Abstract

In this paper, we consider the Bloch eigenvalues and spectrum of the non-self-adjoint differential operator \(L\) generated by the differential expression of odd order \(n\) with periodic \(\mathcal{PT}\) -symmetric coefficients, where \(n>1\) . We study the localizations of the Bloch eigenvalues and the structure of the spectrum. Moreover, we find conditions on the norm of the coefficients under which the spectrum of \(L\) is purely real and coincides with the real line.