On the structure of the essential spectrum of a model many-body Hamiltonian
The author study the spectrum of a model lattice Hamiltonian \(H\) \[ H= \begin{pmatrix} H_{00} & H_{01} & 0 \\ H_{10} & H_{11} & H_{12} \\ 0 & H_{21} & H_{22} \end{pmatrix}, \] describing a system with fluctuating number of particles. The spectral properties of the model are derived in term of the boundary-values of a complex function defined as the kernel of the operator \(H_{11}-z-H_{12}(H_{22}-z)^{-1} H_{12}^*\).
scientific article; zbMATH DE number 5352320