M. Beria, G. P. Brandino, L. Lepori, R. M. Konik, G. Sierra
We outline the application of the truncated conformal space approach (TCSA) to perturbations of $SU(2)_k$ Wess-Zumino-Witten theories. As examples of this methodology, we consider two distinct perturbations of $SU(2)_1$ and one of $SU(2)_2$. $SU(2)_1$ is first perturbed by its spin-1/2 field, a model which is equivalent to the sine-Gordon model at a particular value of its coupling $\beta$. The sine-Gordon spectrum is correctly reproduced as well as the corresponding finite size corrections. We next study $SU(2)_1$ with a marginal current-current perturbation. The TCSA results can be matched to perturbation theory within an appropriate treatment of the UV divergences. Finally, we consider $SU(2)_2$ perturbed by its spin-1 field, which is equivalent to three decoupled massive Majorana fermions.In this case as well the TCSA reproduces accurately the known spectrum.
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http://arxiv.org/abs/1301.0084
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