The most general $\lambda$-deformation of CFTs and integrability

Understand

We show that the CFT with symmetry group $G_{k_1}\times G_{k_2}\times \cdots \times G_{k_n}$ consisting of WZW models based on the same group $G$, but at arbitrary integer levels, admits an integrable deformation depending on $2(n-1)$ continuous parameters.

• We derive the all-loop effective action of the deformed theory and prove integrability.
• We also calculate the exact in the deformation parameters RG flow equations which can be put in a particularly simple compact form.
• This allows a full determination and classification of the fixed points of the RG flow, in particular those that are IR stable.