Hamiltonian analysis of non-projectable modified Hořava–Lifshitz gravity

Non-minimally Coupled Modified Gravity

In this paper we consider a quintom model of dark energy with non-minimal coupling between scalar field and modified gravity which is known f(R) gravity. The Lagrangian for scalar field has been inspired by tachyonic Lagrangian in string theory. Then we obtain the equation of state (EoS), and the condition required for the model parameters when ω crosses over −1. This model shows that for havin...

Non-singular Cosmology in Modified Gravity

A non-singular cosmology is derived in modified gravity (MOG). The universe begins in the distant past in a contracting de Sitter phase, is non-singular at t = 0 and then describes approximately the standard radiation dominated solution before the time of decoupling. The spacetime in the neighborhood of t = 0 is described by Minkowski spacetime in which the Weyl curvature tensor vanishes and th...

Hamiltonian spinfoam gravity

Hamiltonian analysis of n-dimensional Palatini gravity with matter

We consider the Palatini formalism of gravity with cosmological constant Λ coupled to a scalar field φ in n-dimensions. The n-dimensional Einstein equations with Λ can be derived by the variation of the coupled Palatini action provided n > 2. The Hamiltonian analysis of the coupled action is carried out by a 1 + (n− 1) decomposition of the spacetime. It turns out that both Palatini action and H...

Short Distance Non-perturbative Effects of Large Distance Modified Gravity

In a model of large distance modified gravity we compare the nonperturbative Schwarzschild solution of hep-th/0407049 to approximate solutions obtained previously. In the regions where there is a good qualitative agreement between the two, the nonperturbative solution yields effects that could have observational significance. These effects reduce, by a factor of a few, the predictions for the a...