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Coupling between Galileon and massive gravity with composite metrics
Xian Gao, Daisuke Yoshida
We investigate the coupling between a Galileon scalar field and massive gravity through composite metrics. We derive the full set of equations of motion for a flat Friedmann-Robert…
Hamiltonian analysis of spatially covariant gravity
Xian Gao
We perform the Hamiltonian constraint analysis for a wide class of gravity theories that are invariant under spatial diffeomorphism. With very general setup, we show that different…
Covariant Stückelberg analysis of de Rham-Gabadadze-Tolley massive gravity with a general fiducial metric
Xian Gao, Tsutomu Kobayashi, Masahide Yamaguchi +1
The Stückelberg analysis of nonlinear massive gravity in the presence of a general fiducial metric is investigated. We develop a "covariant" formalism for the Stückelberg expansion…
Non-Gaussianity excess problem in classical bouncing cosmologies
Xian Gao, Marc Lilley, Patrick Peter
The simplest possible classical model leading to a cosmological bounce is examined in the light of the non-Gaussianities it can generate. Concentrating solely on the transition bet…
Unifying framework for scalar-tensor theories of gravity
Xian Gao
A general framework for effective theories propagating two tensor and one scalar degrees of freedom is investigated. Geometrically, it describes dynamical foliation of spacelike hy…
Production of non-gaussianities in a bouncing phase
Xian Gao, Marc Lilley, Patrick Peter
We compute the level of non-gaussianities produced by a cosmological bouncing phase in the minimal non-singular setup that lies within the context of General Relativity when the ma…