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From k-essence to generalised Galileons
We determine the most general scalar field theories which have an action that depends on derivatives of order two or less, and have equations of motion that stay second order and lower on flatExpand
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Accelerated universe from gravity leaking to extra dimensions
We discuss the idea that the accelerated universe could be the result of gravitational leakage into extra dimensions over Hubble distances rather than the consequence of a nonzero cosmologicalExpand
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Supernovae, CMB, and gravitational leakage into extra dimensions
We discuss observational constraints coming from CMB and type Ia supernovae for the model of an accelerated universe produced by gravitational leakage into extra dimensions. Our fits indicate thatExpand
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On horizon structure of bimetric spacetimes
We discuss the structure of horizons in spacetimes with two metrics, with applications to the Vainshtein mechanism and other examples. We show, without using the field equations, that if the twoExpand
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Reconstructing the Distortion Function for Nonlocal Cosmology
We consider the cosmology of modified gravity models in which Newton's constant is distorted by a function of the inverse d'Alembertian acting on the Ricci scalar. We derive a technique for choosingExpand
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The radion in brane cosmology
Abstract We consider the homogeneous cosmological radion, which we define as the interbrane distance in a two-brane and Z 2 symmetrical configuration. In a coordinate system where one of the brane isExpand
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Dimming of supernovae by photon-pseudoscalar conversion and the intergalactic plasma
It has been suggested recently that the observed dimming of distant type Ia supernovae may be a consequence of mixing of the photons with very light axions. We point out that the effect of theExpand
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Classifying Galileon $p$-form theories
We provide a complete classification of all abelian gauge invariant $p$-form theories with equations of motion depending only on the second derivative of the field---the $p$-form analogues of theExpand
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On brane world cosmological perturbations
We discuss the scalar cosmological perturbations in a 3-brane world with a 5D bulk. We first show explicitly how the effective perturbed Einstein equations on the brane (involving the Weyl fluid) areExpand
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Multigravity from a discrete extra dimension
Multigravity theories are constructed from the discretization of the extra dimension of five-dimensional gravity. Using an ADM decomposition, the discretization is performed while maintaining theExpand
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