The spectral density of the Rabi model is calculated exactly within a continued fraction approach. It is shown that the method yields a convergent solution.
Cite
@article{arxiv.1204.3856,
title = {Short note on the Rabi model},
author = {K. Ziegler},
journal= {arXiv preprint arXiv:1204.3856},
year = {2012}
}