The consistency of codimension-2 braneworlds and their cosmology (2009)
Charmousis, Christos, Kofinas, Georgios, Papazoglou, Antonios
We study axially symmetric codimension-2 cosmology for a distributional braneworld fueled by a localised 4D perfect fluid, in a 6D Lovelock theory. We argue that only the matching conditions (dubbed...
Einstein-Maxwell-Dilaton theories with a Liouville potential (2009)
Charmousis, Christos, Gouteraux, Blaise, Soda, Jiro
We find and analyse solutions of Einstein's equations in arbitrary d dimensions and in the presence of a scalar field with a Liouville potential coupled to a Maxwell field. We consider spacetimes of...
Strong coupling in Horava gravity (2009)
Charmousis, Christos, Niz, Gustavo, Padilla, Antonio, Saffin, Paul M.
By studying perturbations about the vacuum, we show that Horava gravity suffers from two different strong coupling problems, extending all the way into the deep infra-red. The first of these is...
Properties of codimension-2 braneworlds in six-dimensional Lovelock theory (2009)
Charmousis, Christos, Papazoglou, Antonios
We consider maximally symmetric 3-branes embedded in a six-dimensional bulk spacetime with Lovelock dynamics. We study the properties of the solutions with respect to their induced curvature, their...
The Instability of Vacua in Gauss-Bonnet Gravity (2008)
Charmousis, Christos, Padilla, Antonio
Owing to the quadratic nature of the theory, Einstein-Gauss-Bonnet gravity generically permits two distinct vacuum solutions. One solution (the "Einstein" vacuum) has a well defined limit as the...
Higher order gravity theories and their black hole solutions (2008)
We discuss a particular higher order gravity theory, Lovelock theory, that generalises in higher dimensions, general relativity. After briefly motivating modifications of gravity, we will introduce...
Self-properties of codimension-2 braneworlds (2008)
Charmousis, Christos, Papazoglou, Antonios
We consider four-dimensional de Sitter, flat and anti de Sitter branes embedded in a six-dimensional bulk spacetime whose dynamics is dictated by Lovelock theory. We find, applying a generalised...
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...
Ernst equation and spheroidal coordinates with a cosmological constant term (2007)
We discuss solution generating techniques treating stationary and axially symmetric metrics in the presence of a cosmological constant. Using the recently found extended form of Ernst's complex...
Stealth Acceleration and Modified Gravity (2007)
Charmousis, Christos, Gregory, Ruth, Padilla, Antonio
We show how to construct consistent braneworld models which exhibit late time acceleration. Unlike self-acceleration, which has a de Sitter vacuum state, our models have the standard Minkowski vacuum...
Stealth Acceleration and Modified Gravity (2007)
Charmousis, Christos, Gregory, Ruth, Padilla, Antonio
We show how to construct consistent braneworld models which exhibit late time acceleration. Unlike self-acceleration, which has a de Sitter vacuum state, our models have the standard Minkowski vacuum...
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...
Gauss-Bonnet gravity renders negative tension braneworlds unstable (2007)
Charmousis, Christos, Dufaux, Jean-Francois
We show that the Gauss-Bonnet correction to Einstein gravity induces a gravitational tachyon mode, namely an unstable spin 2 fluctuation, in the Randall-Sundrum I model. We demonstrate that this...
General Gauss-Bonnet brane cosmology (2007)
Charmousis, Christos, Dufaux, Jean-Francois
We consider 5-dimensional spacetimes of constant 3-dimensional spatial curvature in the presence of a bulk cosmological constant. We find the general solution of such a configuration in the presence...
Rotating spacetimes with a cosmological constant (2007)
Charmousis, Christos, Langlois, David, Steer, Daniele, Zegers, Robin
We develop solution-generating techniques for stationary metrics with one angular momentum and axial symmetry, in the presence of a cosmological constant and in arbitrary spacetime dimension. In...
Rotating spacetimes with a cosmological constant (2006)
Charmousis, Christos, Langlois, David, Steer, Daniele, Zegers, Robin
We develop solution-generating techniques for stationary metrics with one angular momentum and axial symmetry, in the presence of a cosmological constant and in arbitrary spacetime dimension. In...
Einstein gravity on an even codimension brane (2006)
Charmousis, Christos, Zegers, Robin
We give the equations of motion for a self-gravitating Dirac p-brane embedded in an even co-dimension spacetime. The dynamics of the bulk are dictated by Lovelock gravity and permit matching...
Einstein gravity on an even codimension brane (2006)
Charmousis, Christos, Zegers, Robin
We give the equations of motion for a self-gravitating Dirac p-brane embedded in an even co-dimension spacetime. The dynamics of the bulk are dictated by Lovelock gravity and permit matching...
Einstein gravity on an even codimension brane (2006)
Charmousis, Christos, Zegers, Robin
We give the equations of motion for a self-gravitating Dirac p-brane embedded in an even co-dimension spacetime. The dynamics of the bulk are dictated by Lovelock gravity and permit matching...
Charmousis, Christos, Gregory, Ruth, Kaloper, Nemanja, Padilla, Antonio
We systematically explore the spectrum of gravitational perturbations in codimension-1 DGP braneworlds, and find a 4D ghost on the self-accelerating branch of solutions. The ghost appears for any...
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,...
Matching conditions for a brane of arbitrary codimension (2005)
Charmousis, Christos, Zegers, Robin
We present matching conditions for distributional sources of arbitrary codimension in the context of Lovelock gravity. Then we give examples, treating maximally symmetric distributional p-branes,...
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...
Einstein gravity on an even codimension brane (2005)
Charmousis, Christos, Zegers, Robin
We give the equations of motion for a self-gravitating Dirac p-brane embedded in an even co-dimension spacetime. The dynamics of the bulk are dictated by Lovelock gravity and permit matching...
Matching conditions for a brane of arbitrary codimension (2005)
Charmousis, Christos, Zegers, Robin
We present matching conditions for distributional sources of arbitrary codimension in the context of Lovelock gravity. Then we give examples, treating maximally symmetric distributional p-branes,...
Einstein gravity on an even codimension brane (2005)
Charmousis, Christos, Zegers, Robin
We give the equations of motion for a self-gravitating Dirac p-brane embedded in an even co-dimension spacetime. The dynamics of the bulk are dictated by Lovelock gravity and permit matching...
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,...
Matching conditions for a brane of arbitrary codimension (2005)
Charmousis, Christos, Zegers, Robin
We present matching conditions for distributional sources of arbitrary codimension in the context of Lovelock gravity. Then we give examples, treating maximally symmetric distributional p-branes,...
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,...
Matching conditions for a brane of arbitrary codimension (2005)
Charmousis, Christos, Zegers, Robin
We present matching conditions for distributional sources of arbitrary codimension in the context of Lovelock gravity. Then we give examples, treating maximally symmetric distributional p-branes,...
Einstein gravity on an even codimension brane (2005)
Charmousis, Christos, Zegers, Robin
We give the equations of motion for a self-gravitating Dirac p-brane embedded in an even co-dimension spacetime. The dynamics of the bulk are dictated by Lovelock gravity and permit matching...
Gauss-Bonnet gravity renders negative tension braneworlds unstable (2003)
Charmousis, Christos, Dufaux, Jean-Francois
We show that the Gauss-Bonnet correction to Einstein gravity induces a gravitational tachyon mode, namely an unstable spin 2 fluctuation, in the Randall-Sundrum I model. We demonstrate that this...
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...
Axisymmetric metrics in arbitrary dimensions (2003)
Charmousis, Christos, Gregory, Ruth
We consider axially symmetric static metrics in arbitrary dimension, both with and without a cosmological constant. The most obvious such solutions have an SO(n) group of Killing vectors representing...
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...
General Gauss-Bonnet brane cosmology (2002)
Charmousis, Christos, Dufaux, Jean-Francois
We consider 5-dimensional spacetimes of constant 3-dimensional spatial curvature in the presence of a bulk cosmological constant. We find the general solution of such a configuration in the presence...
Dilaton spacetimes with a Liouville potential (2001)
We find and study solutions to the Einstein equations in D dimensions coupled to a scalar field source with a Liouville potential under the assumption of D-2 planar symmetry. The general static or...
Self-gravity of Brane Worlds: A New Hierarchy Twist (2001)
Charmousis, Christos, Emparan, Roberto, Gregory, Ruth
We examine the inclusion of brane self-gravity in brane-world scenarios with three or more compact extra dimensions. If the brane is a thin, localized one, then we find that the geometry in its...
General brane cosmologies and their global spacetime structure (2000)
Bowcock, Peter, Charmousis, Christos, Gregory, Ruth
Starting from a completely general standpoint, we find the most general brane-Universe solutions for a three-brane in a five dimensional spacetime. The brane can border regions of spacetime with or...
The dynamics of curved gravitating walls (2000)
Bonjour, Filipe, Charmousis, Christos, Gregory, Ruth
We examine the dynamics of a self-gravitating domain wall using the $\lambda \Phi^4$ model as a specific example. We find that the Nambu motion of the wall is quite generic and dominates the wall...
Wave function of the radion in a brane world (1999)
Charmousis, Christos, Gregory, Ruth, Rubakov, Valery A.
We calculate the linearized metric perturbation corresponding to a massless four-dimensional scalar field, the radion, in a five-dimensional two-brane model of Randall and Sundrum. In this way we...
Thick self-gravitating plane-symmetric domain walls (1999)
Bonjour, Filipe, Charmousis, Christos, Gregory, Ruth
We investigate a self-gravitating thick domain wall for a $\lambda \Phi^4$ potential. The system of scalar and Einstein equations admits two types of non-trivial solutions: domain wall solutions and...
Thick domain wall universes (1999)
Bonjour, Filipe, Charmousis, Christos, Gregory, Ruth
We investigate the spacetime of a thick gravitating domain wall for a general potential $V(\Phi)$. Using general analytical arguments we show that all nontrivial solutions fall into two categories:...