## Comment on "Integrability of the Rabi model"    [PDF]

Alexander Moroz
In his recent letter, Braak suggested that a regular spectrum of the Rabi model was given by the zeroes of a transcendental function $G_\pm(x)$ (cf Eqs. (3)-(5) of Ref. [1]) and highlighted the role of the discrete $\mathbb{Z}_2$-symmetry, or parity, in determining $G_\pm(x)$. We show here to the contrary that one can define a transcendental function $F_0(x)$ and obtain the regular spectrum of the Rabi model as the zeroes of $F_0(x)$ (see Fig. 1) without ever making use of the underlying $\mathbb{Z}_2$-symmetry of the model.
View original: http://arxiv.org/abs/1205.3139