Scale without conformal invariance from integrable deformations of coset CFTs

Abstract

We construct the $\lambda$-model on $SU(3)_k/U(2)_k$ and we compute the one-loop $\beta$-function for the deformation parameter $\lambda$. Its non-compact version for $SU(2,1)_{-k}/U(2)_{-k}$ is also considered, whose target space admits an asymptotic region that can be reached when one of the coordinates becomes large. The asymptotic model can be seen as an integrable deformation of the $SU(2)_k/U(1)$ WZW model together with a linear dilaton and a free boson, where integrability is inherited from the parental $\lambda$-model. By taking an asymptotic double-scaling limit of the $SU(2,1)_{-k}/U(2)_{-k}$ model, we obtain a two-dimensional field theory that is scale-invariant but not conformally invariant at one-loop order. Crucially, this deformation does not admit a Kerr-Schild form, unlike the cases studied in arXiv:2109.05040. However, in a suitable asymptotic regime, scale invariance is enhanced to full conformal invariance. Finally, we construct Type-II supergravity embeddings of the asymptotic model for specific values of the deformation parameter.