Two-field mimetic gravity revisited and Hamiltonian analysis

Understand

We revisit the two-field mimetic gravity model with shift symmetries recently proposed in the literature, especially the problems of degrees of freedom and stabilities.

• We first study the model at the linear cosmological perturbation level by quadratic Lagrangian and Hamiltonian formulations.
• We show that there are actually two (instead of one) scalar degrees of freedom in this model in addition to two tensor modes.
• We then push on the study to the full non-linear level in terms of the Hamiltonian analysis, and confirm our result from the linear perturbation theory.