2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/151587An extended Hubbard model with phonons is considered on a D-dimensional lattice. The symmetries of the model are studied in various cases. It is shown that for a certain choice of the parameters a superconducting SU_q(2) holds as a true quantum symmetry - but only for D=1. In a natural basis the symmetry requires vanishing local phonon coupling; a quantum symmetric Hubbard model without phonons can then be obtained by a mean field approximation.plain tex, 7 pagesCondensed MatterHigh Energy Physics - TheoryQuantum Algebratext