Racetrack Inflation and Cosmic Strings (2008)
Brax, Philippe, Van De Bruck, Carsten, Davis, Anne-Christine, Davis, Stephen C., Jeannerot, Rachel, Postma, Marieke
We consider the coupling of racetrack inflation to matter fields as realised in the D3/D7 brane system. In particular, we investigate the possibility of cosmic string formation in this system. We...
SUGRA chaotic inflation and moduli stabilisation (2008)
Davis, Stephen C., Postma, Marieke
Chaotic inflation predicts a large gravitational wave signal which can be tested by the upcoming Planck satellite. We discuss a SUGRA implementation of chaotic inflation in the presence of moduli...
Mimicking general relativity in the solar system (2008)
Amendola, Luca, Charmousis, Christos, Davis, Stephen C.
In order for a modified gravity model to be a candidate for cosmological dark energy it has to pass stringent local gravity experiments. We find that a Brans-Dicke (BD) theory with well-defined...
Successfully combining SUGRA hybrid inflation and moduli stabilisation (2008)
Inflation and moduli stabilisation mechanisms work well independently, and many string-motivated supergravity models have been proposed for them. However a complete theory will contain both, and...
The Robustness of n_s < 0.95 in Racetrack Inflation (2007)
Brax, Ph., Davis, Stephen C., Postma, M.
A spectral index n_s < 0.95 appears to be a generic prediction of racetrack inflation models. Reducing a general racetrack model to a single-field inflation model with a simple potential, we obtain...
D-term Uplifted Racetrack Inflation (2007)
Brax, Philippe, Davis, Anne-Christine, Davis, Stephen C., Jeannerot, Rachel, Postma, Marieke
It is shown that racetrack inflation can be implemented in a moduli stabilisation scenario with a supersymmetric uplifting D-term. The resulting model is completely described by an effective...
Solar System Constraints on f(G) Dark Energy (2007)
Corrections to solar system gravity are derived for f(G) gravity theories, in which a function of the Gauss-Bonnet curvature term is added to the gravitational action. Their effects on Newton's law,...
Solar System Constraints on Gauss-Bonnet Dark Energy (2007)
Quadratic curvature Gauss-Bonnet gravity may be the solution to the dark energy problem, but a large coupling strength is required. This can lead to conflict with laboratory and planetary tests of...
Warping and F-term uplifting (2007)
Brax, Philippe, Davis, Anne-Christine, Davis, Stephen C., Jeannerot, Rachel, Postma, Marieke
We analyse the effective supergravity model of a warped compactification with matter on D3 and D7-branes. We find that the main effect of the warp factor is to modify the F-terms while leaving the...
Solar System Constraints on Gauss-Bonnet Mediated Dark Energy (2007)
Amendola, Luca, Charmousis, Christos, Davis, Stephen C.
Although the Gauss-Bonnet term is a topological invariant for general relativity, it couples naturally to a quintessence scalar field, modifying gravity at solar system scales. We determine the solar...
Scalar brane backgrounds in higher order curvature gravity (2007)
Charmousis, Christos, Davis, Stephen C., Dufaux, Jean-Francois
We investigate maximally symmetric brane world solutions with a scalar field. Five-dimensional bulk gravity is described by a general lagrangian which yields field equations containing no higher than...
Solar System Constraints on Gauss-Bonnet Mediated Dark Energy (2007)
Amendola, Luca, Charmousis, Christos, Davis, Stephen C.
Although the Gauss-Bonnet term is a topological invariant for general relativity, it couples naturally to a quintessence scalar field, modifying gravity at solar system scales. We determine the solar...
Fire Resistant Composite Closed Cell Foam and Nonwoven Textiles for Tents and Shelters (2007)
Davis, Stephen C., Kalberer, Jennifer L.
The objective of the overall effort is to develop a fire resisting elastomeric closed cell foam as a component of a nonwoven fabric -- foam composite for fabrication of rapidly deployed shelters. The...
Microphysics of Cosmic Strings in Supersymmetric and Grand Unified Theories (2006)
In this thesis we investigate the microphysics of cosmic strings in non-minimal quantum field theories. In particular we consider theories in which fermion fields couple to the strings, and those...
Moduli Corrections to D-term Inflation (2006)
Brax, Ph., Davis, A. C., Davis, Stephen C., Jeannerot, R., Postma, M.
We present a D-term hybrid inflation model, embedded in supergravity with moduli stabilisation. Its novel features allow us to overcome the serious challenges of combining D-term inflation and moduli...
Brane World Cosmic String Interaction (2006)
It is shown that brane world gravity produces an attractive force between cosmic strings, in contrast to conventional Einstein gravity. This force is sufficient for stable bound states of Type II...
Coupling Hybrid Inflation to Moduli (2006)
Brax, Ph., Davis, A. C., Davis, Stephen C.
Hybrid inflation can be realised in low-energy effective string theory, as described using supergravity. We find that the coupling of moduli to F-term hybrid inflation in supergravity leads to a...
Cosmic D-Strings and Vortons in Supergravity (2006)
Brax, Ph., Davis, A. C., Davis, Stephen C.
Recent developments in string inspired models of inflation suggest that D-strings are formed at the end of inflation. Within the supergravity model of D-strings there are 2(n-1) chiral fermion zero...
Fermionic Zero Modes of Supergravity Cosmic Strings (2006)
Brax, Ph., Davis, A. C., Davis, Stephen C.
Recent developments in string theory suggest that cosmic strings could be formed at the end of brane inflation. Supergravity provides a realistic model to study the properties of strings arising in...
Constraints on Gauss-Bonnet Gravity in Dark Energy Cosmologies (2005)
Amendola, Luca, Charmousis, Christos, Davis, Stephen C.
Accelerating four dimensional cosmologies, whose dark energy component includes the general contribution from second order gravity terms, are investigated. In particular the Gauss-Bonnet invariant,...
Constraints on Gauss-Bonnet Gravity in Dark Energy Cosmologies (2005)
Amendola, Luca, Charmousis, Christos, Davis, Stephen C.
Models with a scalar field coupled to the Gauss-Bonnet Lagrangian appear naturally from Kaluza-Klein compactifications of pure higher-dimensional gravity. We study linear, cosmological perturbations...
Vacuum Decay on a Brane World (2005)
Davis, Stephen C., Brechet, Sylvain
The bubble nucleation rate for a first order phase transition occurring on a brane world is calculated. Both the Coleman-de Luccia thin wall instanton and the Hawking-Moss instanton are considered....
Local Axion Cosmic Strings from Superstrings (2005)
Davis, Stephen C., Binetruy, Pierre, Davis, Anne-Christine
Axionic cosmic string solutions are investigated in a superstring motivated model with a pseudo-anomalous U(1) gauge symmetry. The inclusion of a gauge field and spatially varying dilaton allow local...
Constraints on Gauss-Bonnet Gravity in Dark Energy Cosmologies (2005)
Amendola, Luca, Charmousis, Christos, Davis, Stephen C.
Accelerating four dimensional cosmologies, whose dark energy component includes the general contribution from second order gravity terms, are investigated. In particular the Gauss-Bonnet invariant,...
Constraints on Gauss-Bonnet Gravity in Dark Energy Cosmologies (2005)
Amendola, Luca, Charmousis, Christos, Davis, Stephen C.
Accelerating four dimensional cosmologies, whose dark energy component includes the general contribution from second order gravity terms, are investigated. In particular the Gauss-Bonnet invariant,...
Gauss-Bonnet Brane World Gravity with a Scalar Field (2004)
The effective four-dimensional, linearised gravity of a brane world model with one extra dimension and a single brane is analysed. The model includes higher order curvature terms (such as the...
Modified Large Distance Newton Potential on a Gauss-Bonnet Brane World (2004)
Gravity on a brane world with higher order curvature terms and a conformally coupled bulk scalar field is investigated. Solutions with non-standard large distance gravity are described. It is not...
Gravity on a Dilatonic Gauss-Bonnet Brane World (2004)
The effective four-dimensional, linearised gravity of a Randall-Sundrum-like brane world model is analysed. The model includes higher order curvature terms (such as the Gauss-Bonnet term) and a...
Scalar-Tensor Gravity on a Gauss-Bonnet Brane World (2004)
The effective four-dimensional, linearised gravity for a brane world model with higher order curvature terms and a bulk scalar field is analysed. Large and small distance gravitational laws are...
Scalar brane backgrounds in higher order curvature gravity (2003)
Charmousis, Christos, Davis, Stephen C., Dufaux, Jean-Francois
We investigate maximally symmetric brane world solutions with a scalar field. Five-dimensional bulk gravity is described by a general lagrangian which yields field equations containing no higher than...
Improving the `self-tuning' mechanism with a Gauss-Bonnet term (2002)
The effects of higher order gravity terms on a dilatonic brane world model are discussed. For a single positive tension flat 3-brane, and one infinite extra dimension, we present a particular class...
Generalised Israel Junction Conditions for a Gauss-Bonnet Brane World (2002)
In spacetimes of dimension greater than four it is natural to consider higher order (in R) corrections to the Einstein equations. In this letter generalized Israel junction conditions for a membrane...
Avoidance of Naked Singularities in Dilatonic Brane World Scenarios with a Gauss-Bonnet Term (2002)
Binetruy, Pierre, Charmousis, Christos, Davis, Stephen C, Dufaux, Jean-Francois
We consider, in 5 dimensions, the low energy effective action induced by heterotic string theory including the leading stringy correction of order alpha'. In the presence of a single positive tension...
Brane Cosmology Solutions with Bulk Scalar Fields (2001)
Brane cosmologies with static, five-dimensional and Z_2 symmetric bulks are analysed. A general solution generating mechanism is outlined. The qualatitive cosmological behaviour of all such solutions...
Cosmological Brane World Solutions with Bulk Scalar Fields (2001)
Cosmological brane world solutions are found for five-dimensional bulk spacetimes with a scalar field. A supergravity inspired method for obtaining static solutions is combined with a method for...
Cosmological Phase Transitions in a Brane World (2000)
Davis, Stephen C., Perkins, Warren B., Davis, Anne-Christine, Vernon, Ian R.
In brane world scenarios the Friedmann equation is modified, resulting in an increased expansion at early times. This has important effects on cosmological phase transitions which we investigate,...
Brane World Linearized Cosmic String Gravity (2000)
The gravitational properties of cosmic strings in the Randall-Sundrum brane world scenario are investigated. Using a gauge in which the brane remains straight, the leading order corrections to the...
Cosmic Strings and Cooper Pairs (2000)
It is shown that it is possible for bound fermions on a cosmic string to form a superconducting state. Due to the attractive force between them, particles moving in opposite directions along the...
Brane World Cosmology Without the Z_2 Symmetry (2000)
Davis, Anne-Christine, Vernon, Ian, Davis, Stephen C., Perkins, Warren B.
The Friedmann equation for a positive tension brane situated between two bulk spacetimes that posses the same 5D cosmological constant, but which does not posses a Z_2 symmetry of the metric itself...
The Fate of Cosmic String Zero Modes (2000)
Davis, Anne-Christine, Davis, Stephen C., Perkins, Warren B.
Cosmic strings in realistic particle physics models have fermion zero modes in the string core. Such zero modes change the underlying cosmology; for example, the string can carry a current. We...
Cosmic String Current Stability (1999)
Davis, Stephen C., Perkins, Warren B., Davis, Anne-Christine
The stability of fermionic charge carriers on cosmic strings is considered. We show that neutral fermion currents in cosmic strings are always chiral or time-like, in contrast to the case of bosonic...
Destruction of Fermion Zero Modes on Cosmic Strings (1999)
I examine the existence of zero energy fermion solutions (zero modes) on cosmic strings in an SO(10) grand unified theory. The current carrying capability of a cosmic string formed at one phase...
Cosmic Strings, Zero Modes and SUSY breaking in Nonabelian N=1 Gauge Theories (1997)
Davis, Stephen C., Davis, Anne C., Trodden, Mark
We investigate the microphysics of cosmic strings in Nonabelian gauge theories with N=1 supersymmetry. We give the vortex solutions in a specific example and demonstrate that fermionic...
Cosmic String Zero Modes and Multiple Phase Transitions (1997)
Davis, Stephen C., Davis, Anne-Christine, Perkins, Warren B.
The zero modes and current carrying capability of a cosmic string formed at one phase transition can be modified at subsequent phase transitions. A new, generalised index theorem is derived that is...
N=1 Supersymmetric Cosmic Strings (1997)
Davis, Stephen C., Davis, Anne-Christine, Trodden, Mark
We investigate the microphysics of supersymmetric cosmic strings. In particular we focus on the vortices admitted by N=1 supersymmetric abelian Higgs models. We find the vortex solutions and...
Microphysics of SO(10) Cosmic Strings (1996)
Davis, Anne-Christine, Davis, Stephen C.
We uncover a rich microphysical structure for SO(10) cosmic strings. For the abelian string the electroweak symmetry is restored around it in a region depending on the electroweak scale. A rich...