Note on an extended chiral bosons system contextualized in a modified gauge-unfixing formalism

We analyze the Hamiltonian structure of an extended chiral bosons theory in which the self-dual constraint is introduced via a control α -parameter. The system has two second-class constraints in the non-critical regime and an additional one in the critical regime. We use a modified gauge-unfixing (GU) formalism to derive a first-class system, disclosing hidden symmetries. To this end, we choose one of the second-class constraints to build a corresponding gauge symmetry generator. The worked out procedure converts second-class variables into first-class ones allowing the lifting of gauge symmetry. Any function of these GU variables will also be invariant. We obtain the GU Hamiltonian and Lagrangian densities in a generalized context containing the Srivastava and Floreanini-Jackiw models as particular cases. Additionally, we observe that the resulting GU Lagrangian presents similarities to the Siegel invariant Lagrangian which is known to be suitable for describing chiral bosons theory with classical gauge invariance, however broken at quantum level. The final results signal a possible equivalence between our invariant Lagrangian obtained from the modified GU formalism and the Siegel invariant Lagrangian, with a distinct gauge symmetry.