On creating new essential spectrum by self-adjoint extension of gapped operators

Springer Science and Business Media LLC - Tập 15 - Trang 1-24 - 2024
Alessandro Michelangeli1,2,3
1Department of Mathematics and Natural Sciences, Prince Mohammad Bin Fahd University, Al Khobar, Saudi Arabia
2Hausdorff Center for Mathematics, University of Bonn, Bonn, Germany
3TQT Trieste Institute for Theoretical Quantum Technologies, Trieste, Italy

Tóm tắt

Given a densely defined and gapped symmetric operator with infinite deficiency index, it is shown how self-adjoint extensions admitting arbitrarily prescribed portions of the gap as essential spectrum are identified and constructed within a general extension scheme. The emergence of new spectrum in the gap by self-adjoint extension is a problem with a long history and recent deep understanding, and yet it remains topical in several recent applications. Whereas it is already an established fact that, in case of infinite deficiency index, any kind of spectrum inside the gap can be generated by a suitable self-adjoint extension, the present discussion has the virtue of showing the clean and simple operator-theoretic mechanism of emergence of such extensions.

Tài liệu tham khảo

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