Abstract We propose a category of bundles in order to perform Lagrangian reduction by stages covariant Field Theory. This plays an analogous role Lagrange–Poincaré Mechanics and includes both jet reduced configuration spaces. Furthermore, we analyze the resulting reconstruction condition formulate Noether theorem this context. Finally, model molecular strand with rotors is seen as application t...

Abstract: We derive the gravitational equations of motion of general theories of gravity from thermodynamics applied to a local Rindler horizon through any point in spacetime. Specifically, for a given theory of gravity, we substitute the corresponding Wald entropy into the Clausius relation. Our approach works for all diffeomorphism-invariant theories of gravity in which the Lagrangian is a po...

We analyze the implications of having a divergent speed of sound in k-essence cosmological models. We first study a known theory of that kind, for which the Lagrangian density depends linearly on the time derivative of the k-field. We show that consistency requires that the potential of the k-field be of the inverse square form. Then, we review the known result that the corresponding power-law ...