Gomis Torné, JoaquimLonghi, Giorgio2019-10-112019-10-112016-01-272470-0010https://hdl.handle.net/2445/142200We study the canonical realization of Bondi-Metzner-Sacks symmetry for a massive scalar field introduced by Longhi and Materassi [J. Math. Phys. 40, 480 (1999)]. We construct an invariant scalar product for the generalized momenta. As a consequence we introduce a quadratic Casimir with the supertranslations.4 p.application/pdfeng(c) American Physical Society, 2016Teoria quànticaSimetria (Física)Quantum theorySymmetry (Physics)info:eu-repo/semantics/article6691552019-10-11info:eu-repo/semantics/openAccess