Very large scale structures in growing neutrino quintessence (2009)
Wintergerst, Nico, Pettorino, Valeria, Mota, David F., Wetterich, Christof
A quintessence scalar field or cosmon interacting with neutrinos can have important effects on cosmological structure formation. Within growing neutrino models the coupling becomes effective only in...
Perturbations in electromagnetic dark energy (2009)
Jimenez, Jose Beltran, Koivisto, Tomi S., Maroto, Antonio L., Mota, David F.
It has been recently proposed that the presence of a temporal electromagnetic field on cosmological scales could explain the phase of accelerated expansion that the universe is currently undergoing....
Inflation from N-Forms and its stability (2009)
Koivisto, Tomi S., Mota, David F., Pitrou, Cyril
Anisotropic and isotropic slow-roll inflation supported by n-forms are sought. Canonical field strengths and their duals are taken into account, and they are allowed to have a potential and also,...
Clustering in growing neutrino cosmologies (2009)
Pettorino, Valeria, Mota, David F., Robbers, Georg, Wetterich, Christof
We show that growing neutrino models, in which the growing neutrino mass stops the dynamical evolution of a dark energy scalar field, lead to a substantial neutrino clustering on the scales of...
Probing Dark Energy at Galactic and Cluster Scales (2008)
We investigate dark matter halo properties as a function of a time--varying dark energy equation of state. The dynamics of the collapse of the halo is governed by the form of the quintessence...
Testing Alternative Theories of Dark Matter with the CMB (2008)
Li, Baojiu, Barrow, John D., Mota, David F., Zhao, HongSheng
We propose a method to study and constrain modified gravity theories for dark matter using CMB temperature anisotropies and polarization. We assume that the theories considered here have already...
Vector Field Models of Inflation and Dark Energy (2008)
Koivisto, Tomi S., Mota, David F.
We consider several new classes of viable vector field alternatives to the inflaton and quintessence scalar fields. Spatial vector fields are shown to be compatible with the cosmological anisotropy...
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...
Anisotropic Dark Energy: Dynamics of Background and Perturbations (2008)
Koivisto, Tomi, Mota, David F.
We investigate cosmologies where the accelerated expansion of the Universe is driven by a field with an anisotropic equation of state. We model such scenarios within the Bianchi I framework,...
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...
CMB Anisotropies and Inflation from Non-Standard Spinors (2007)
Boehmer, Christian G., Mota, David F.
The apparent alignment of the cosmic microwave background multipoles on large scales challenges the standard cosmological model. Scalar field inflation is isotropic and cannot account for the...
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...
Detecting a Lorentz-Violating Field in Cosmology (2007)
Li, Baojiu, Mota, David F., Barrow, John D.
We consider cosmology in the Einstein-aether theory (the generally covariant theory of gravitation coupled to a dynamical timelike Lorentz-violating vector field) with a linear aether-Lagrangian. The...
Easson, Damien A., Gregory, Ruth, Mota, David F., Tasinato, Gianmassimo, Zavala, Ivonne
We study the cosmological implications of including angular motion in the DBI brane inflation scenario. The non-canonical kinetic terms of the Dirac-Born-Infeld action give an interesting alternative...
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...
Detecting Chameleons through Casimir Force Measurements (2007)
Brax, Philippe, Van De Bruck, Carsten, Davis, Anne-Christine, Mota, David F., Shaw, Douglas
The best laboratory constraints on strongly coupled chameleon fields come not from tests of gravity per se but from precision measurements of the Casimir force. The chameleonic force between two...
Balaguera-Antolinez, Andres, Mota, David F., Nowakowski, Marek
We explore the effects of a positive cosmological constant on astrophysical and cosmological configurations described by a polytropic equation of state. We derive the conditions for equilibrium and...
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...
The Cosmology of Ricci-Tensor-Squared Gravity in the Palatini Variational Approach (2007)
Li, Baojiu, Barrow, John D., Mota, David F.
We consider the cosmology of the Ricci-tensor-squared gravity in the Palatini variational approach. The gravitational action of standard general relativity is modified by adding a function...
Accelerating Cosmologies with an Anisotropic Equation of State (2007)
Koivisto, Tomi, Mota, David F.
If the dark energy equation of state is anisotropic, the expansion rate of the universe becomes direction-dependent at late times. We show that such models are not only cosmologically viable but that...
The Cosmology of Modified Gauss-Bonnet Gravity (2007)
Li, Baojiu, Barrow, John D., Mota, David F.
We consider the cosmology where some function f(G) of the Gauss-Bonnet term G is added to the gravitational action to account for the late-time accelerating expansion of the universe. The covariant...
Neutrino Dark Energy -- Revisiting the Stability Issue (2007)
Bjaelde, Ole Eggers, Brookfield, Anthony W., Van De Bruck, Carsten, Hannestad, Steen, Mota, David F., Schrempp, Lily, ...
A coupling between a light scalar field and neutrinos has been widely discussed as a mechanism for linking (time varying) neutrino masses and the present energy density and equation of state of dark...
Koivisto, Tomi, Mota, David F.
We investigate a string-inspired dark energy scenario featuring a scalar field with a coupling to the Gauss-Bonnet invariant. Such coupling can trigger the onset of late dark energy domination after...
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...
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 and Astrophysical Constraints of Gauss-Bonnet Dark Energy (2006)
Koivisto, Tomi, Mota, David F.
Cosmological consequences of a string-motivated dark energy scenario featuring a scalar field coupled to the Gauss-Bonnet invariant are investigated. We study the evolution of the universe in such a...
Dark Energy Anisotropic Stress and Large Scale Structure Formation (2005)
Koivisto, Tomi, Mota, David F.
We investigate the consequences of an imperfect dark energy component on the large scale structure. A phenomenological three parameter fluid description is used to study the effect of dark energy on...
Multiple Inflation, Cosmic String Networks and the String Landscape (2005)
Burgess, C. P., Easther, Richard, Mazumdar, Anupam, Mota, David F., Multamaki, Tuomas
Motivated by the string landscape we examine scenarios for which inflation is a two-step process, with a comparatively short inflationary epoch near the string scale and a longer period at a much...
Qualitative Analysis of Universes with Varying Alpha (2002)
Barrow, John D., Mota, David F.
Assuming a Friedmann universe which evolves with a power-law scale factor, $a=t^{n}$, we analyse the phase space of the system of equations that describes a time-varying fine structure 'constant',...