Studying the perturbed Wess–Zumino–Novikov–Witten SU(2)kSU(2)k theory using the truncated conformal spectrum approach

We study the SU(2)kSU(2)k Wess–Zumino–Novikov–Witten (WZNW) theory perturbed by the trace of the primary field in the adjoint representation, a theory governing the low-energy behavior of a class of strongly correlated electronic systems. While the model is non-integrable, its dynamics can be investigated using the numerical technique of the truncated conformal spectrum approach combined with numerical and analytical renormalization groups (TCSA + RG). The numerical results so obtained provide support for a semiclassical analysis valid at k≫1k≫1. Namely, we find that the low energy behavior is sensitive to the sign of the coupling constant, λ  . Moreover, for λ>0λ>0 this behavior depends on whether k is even or odd. With k even, we find definitive evidence that the model at low energies is equivalent to the massive O(3) sigma model. For k odd, the numerical evidence is more equivocal, but we find indications that the low energy effective theory is critical.