Constraint Algebra in Bigravity
Published 2020-06-29Version 1
The constraint algebra is derived in the 2nd order tetrad Hamiltonian formalism of the bigravity. This is done by a straightforward calculation without involving any insights, implicit functions, and Dirac brackets. The tetrad approach is the only way to present the bigravity action as a linear functional of lapses and shifts, and the Hassan-Rosen transform (characterized as ``complicated redefinition of the shift variable'' according to the authors) appears here not as an ansatz but as a fixing of a Lagrange multiplier. A comparison of this approach with the others is provided.