10175 1812.04033 10.1007/JHEP03(2019)094 94 94 The most general λ-deformation of CFTs and integrability Regular Article - Theoretical Physics 1 21 2019 3 18 2018 12 18 2019 3 11 2019 3 18 The Author(s) 2019 13130 2019 2019 3 3 George Georgiou georgiou@inp.demokritos.gr Konstantinos Sfetsos ksfetsos@phys.uoa.gr 0000 0001 2155 0800 grid.5216.0 Department of Nuclear and Particle Physics, Faculty of Physics National and Kapodistrian University of Athens Athens 15784 Greece Abstract We show that the CFT with symmetry group G k 1 × G k 2 × ⋯ × G k n $$ {G}_{k_1}\times {G}_{k_2}\times \cdots \times {G}_{k_n} $$ 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 of those that are IR stable. The models under consideration provide concrete realizations of integrable flows between CFTs. We also consider non-Abelian T-duality type limits. Keywords Field Theories in Lower Dimensions Integrable Field Theories Sigma Models Bosonic Strings ArXiv ePrint: 1812.04033