On the spectrum of the Heisenberg Hamiltonian

M. Łabuz, Andrzej Wal

Daddy Balondo Iyela, Prosper Lufungula Nkwambiaya, Nestor Anzola Kibamba

In this paper, three examples of non-Hermitian Hamiltonians were presented on which an approach was applied based on the Heisenberg equation of motion, namely a first-order equation in the coordinate and momentum.

Marek S. Wartak, Ching-Yao Fong

Jacek Karwowski, Dorota Biel�nska-Wa, Jacek Jurkowski

An approach aimed at approximating the extreme (the lowest and/or the highest) eigenvalues of matrices representing many-electron model Hamiltonians from a knowledge of several spectral density distribution moments is proposed. A detailed discussion of the Heisenberg spin Hamiltonian spectrum is presented as an example of an application. © 1996 John Wiley & Sons, Inc.

Edwin Pedrozo-Peñafiel, Simone Colombo, Albert F. Adiyatullin +4 more

Sonja Predin

We investigate of the relationship between the entanglement and subsystem Hamiltonians in the perturbative regime of strong coupling between subsystems. One of the two conditions that guarantees the proportionality between these Hamiltonians obtained by using the nondegenerate perturbation theory within the first order is that the unperturbed ground state has a trivial entanglement Hamiltonian. Furthermore, we study the entanglement Hamiltonian of the Heisenberg ladders in a time-dependent magnetic field using the degenerate perturbation theory, where couplings between legs are considered as a perturbation. In this case, when the ground state is two-fold degenerate, and the entanglement Hamiltonian is proportional to the Hamiltonian of a chain within first-order perturbation theory, even then also the unperturbed ground state has a nontrivial entanglement spectrum.