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math-ph2025
Local perturbations of block Toeplitz matrices
Lars Koekenbier, Hermann Schulz-Baldes
This work is about the asymptotic spectral theory of tridiagonal Toeplitz matrices with matrix entries, with periodicity broken on a finite number of entries. Varying the ranks of…
math-ph2024
Transfer matrix analysis of non-hermitian Hamiltonians: asymptotic spectra and topological eigenvalues
Lars Koekenbier, Hermann Schulz-Baldes
Transfer matrix techniques are used to provide a new proof of Widom's results on the asymptotic spectral theory of finite block Toeplitz matrices. Furthermore, a rigorous treatment…
math-ph2023
Spectral localizer for line-gapped non-hermitian systems
Alexander Cerjan, Lars Koekenbier, Hermann Schulz-Baldes
Short-ranged and line-gapped non-hermitian Hamiltonians have strong topological invariants given by an index of an associated Fredholm operator. It is shown how these invariants ca…