The Effect of a Chameleon Scalar Field on the Cosmic Microwave Background (2009)
Davis, Anne-Christine, Schelpe, Camilla A. O., Shaw, Douglas J.
We show that a direct coupling between a chameleon-like scalar field and photons can give rise to a modified Sunyaev-Zel'dovich (SZ) effect in the Cosmic Microwave Background (CMB). The coupling...
Active Galactic Nuclei Shed Light on Axion-like-Particles (2009)
Burrage, Clare, Davis, Anne-Christine, Shaw, Douglas J.
We demonstrate that the scatter in the luminosity relations of astrophysical objects can be used to search for axion-like-particles (ALPs). This analysis is applied to observations of active galactic...
Detecting Chameleons: The Astronomical Polarization Produced by Chameleon-like Scalar Fields (2008)
Burrage, Clare, Davis, Anne-Christine, Shaw, Douglas J.
We show that a coupling between chameleon-like scalar fields and photons induces linear and circular polarization in the light from astrophysical sources. In this context chameleon-like scalar fields...
Varying Alpha: New Constraints from Seasonal Variations (2008)
Barrow, John D., Shaw, Douglas J.
We analyse the constraints obtained from new atomic clock data on the possible time variation of the fine structure `constant' and the electron-proton mass ratio and show how they are strengthened...
f(R) Gravity and Chameleon Theories (2008)
Brax, Philippe, Van De Bruck, Carsten, Davis, Anne-Christine, Shaw, Douglas J.
We analyse f(R) modifications of Einstein's gravity as dark energy models in the light of their connection with chameleon theories. Formulated as scalar-tensor theories, the f(R) theories imply the...
Microscopic and Macroscopic Behaviors of Palatini Modified Gravity Theories (2008)
Li, Baojiu, Mota, David F., Shaw, Douglas J.
We show that, within modified gravity, the non-linear nature of the field equations implies that the usual naive averaging procedure (replacing the microscopic energy-momentum by its cosmological...
Beyond the Chameleon Mechanism (2008)
Mota, David F., Shaw, Douglas J.
As a result of non-linear self-interactions, in chameleon theories where the field couples to matter much more strongly than gravity does, the fifth force between two bodies with thin-shell is...
Indistinguishable Macroscopic Behaviour of Palatini Gravities and General Relativity (2008)
Li, Baojiu, Mota, David F., Shaw, Douglas J.
We show that, within some modified gravity theories, such as the Palatini models, the non-linear nature of the field equations implies that the usual naive averaging procedure (replacing the...
Some Late-time Asymptotics of General Scalar-Tensor Cosmologies (2007)
Barrow, John D., Shaw, Douglas J.
We study the asymptotic behaviour of isotropic and homogeneous universes in general scalar-tensor gravity theories containing a p=-rho vacuum fluid stress and other sub-dominant matter stresses. It...
Hidden in the Light: Magnetically Induced Afterglow from Trapped Chameleon Fields (2007)
Gies, Holger, Mota, David F., Shaw, Douglas J.
We propose an afterglow phenomenon as a unique trace of chameleon fields in optical experiments. The vacuum interaction of a laser pulse with a magnetic field can lead to a production and subsequent...
On the Magnitude of Dark Energy Voids and Overdensities (2007)
Mota, David F., Shaw, Douglas J., Silk, Joseph
We investigate the clustering of dark energy within matter overdensities and voids. In particular, we derive an analytical expression for the dark energy density perturbations, which is valid both in...
An Improved Semi-Analytical Spherical Collapse Model for Non-linear Density Evolution (2007)
Shaw, Douglas J., Mota, David F.
We derive a semi-analytical extension of the spherical collapse model of structure formation that takes account of the effects of deviations from spherical symmetry and shell crossing which are...
Detecting Seasonal Changes in the Fundamental Constants (2007)
We show that if one or more of the `constants' of Nature can vary then their values, as measured in the laboratory, should oscillate over the year in a very particular way. These seasonal changes in...
Mota, David F., Shaw, Douglas J.
We show that, as a result of non-linear self-interactions, it is feasible, at least in light of the bounds coming from terrestrial tests of gravity, measurements of the Casimir force and those...
Observable Effects of Scalar Fields and Varying Constants (2006)
Barrow, John D., Shaw, Douglas J.
We show by using the method of matched asymptotic expansions that a sufficient condition can be derived which determines when a local experiment will detect the cosmological variation of a scalar...
Strongly Coupled Chameleon Fields: New Horizons in Scalar Field Theory (2006)
Mota, David F., Shaw, Douglas J.
We show that as a result of non-linear self-interactions, scalar field theories that couple to matter much more strongly than gravity are not only viable but could well be detected by a number of...
Cosmology in three dimensions: steps towards the general solution (2006)
Barrow, John D., Shaw, Douglas J., Tsagas, Christos G.
We use covariant and first-order formalism techniques to study the properties of general relativistic cosmology in three dimensions. The covariant approach provides an irreducible decomposition of...
Shaw, Douglas J., Barrow, John D.
We investigate the conditions under which cosmological variations in physical `constants' and scalar fields are detectable on the surface of local gravitationally-bound systems, such as planets, in...
Local Experiments See Cosmologically Varying Constants (2005)
Shaw, Douglas J., Barrow, John D.
We describe a rigorous construction, using matched asymptotic expansions, which establishes under very general conditions that local terrestrial and solar-system experiments will measure the effects...
Shaw, Douglas J., Barrow, John D.
We apply the method of matched asymptotic expansions to analyse whether cosmological variations in physical `constants' and scalar fields are detectable, locally, on the surface of local...
We note that in extensions of the Standard Model that allow for a varying fine structure constant, alpha, all matter species, apart from right-handed neutrinos, will gain an intrinsic electric dipole...
Varying Couplings in Electroweak Theory (2004)
Shaw, Douglas J., Barrow, John D.
We extend the theory of Kimberly and Magueijo for the spacetime variation of the electroweak couplings in the unified Glashow-Salam-Weinberg model of the electroweak interaction to include quantum...
A non-associative approach to the finite projective plane conjecture. (1995)
Dissertation (Ph.D.)--University of Michigan