## Resumen

The conformal symmetry algebra in 2D (Diff(S^{1})⊕Diff(S^{1})) is shown to be related to its ultra/non-relativistic version (BMS_{3}≈GCA_{2}) through a nonlinear map of the generators, without any sort of limiting process. For a generic classical CFT_{2}, the BMS_{3} generators then emerge as composites built out from the chiral (holomorphic) components of the stress-energy tensor, T and T¯ , closing in the Poisson brackets at equal time slices. Nevertheless, supertranslation generators do not span Noetherian symmetries. BMS_{3} becomes a bona fide symmetry once the CFT_{2} is marginally deformed by the addition of a TT¯ term to the Hamiltonian. The generic deformed theory is manifestly invariant under diffeomorphisms and local scalings, but it is no longer a CFT_{2} because its energy and momentum densities fulfill the BMS_{3} algebra. The deformation can also be described through the original CFT_{2} on a curved metric whose Beltrami differentials are determined by the variation of the deformed Hamiltonian with respect to T and T¯. BMS_{3} symmetries then arise from deformed conformal Killing equations, corresponding to diffeomorphisms that preserve the deformed metric and stress-energy tensor up to local scalings. As an example, we briefly address the deformation of N free bosons, which coincides with ultra-relativistic limits only for N = 1. Furthermore, Cardy formula and the S-modular transformation of the torus become mapped to their corresponding BMS_{3} (or flat) versions.

Idioma original | Inglés |
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Número de artículo | 133 |

Publicación | Journal of High Energy Physics |

Volumen | 2021 |

N.º | 11 |

DOI | |

Estado | Publicada - 2021 |

Publicado de forma externa | Sí |

### Nota bibliográfica

Publisher Copyright:© 2021, The Author(s).

## Áreas temáticas de ASJC Scopus

- Física nuclear y de alta energía