Hamiltonian formulation of f(Riemann) theories of gravity (2009)
Deruelle, Nathalie, Sasaki, Misao, Sendouda, Yuuiti, Yamauchi, Daisuke
We present a canonical formulation of gravity theories whose Lagrangian is an arbitrary function of the Riemann tensor. Our approach allows a unified treatment of various subcases and an easy...
Various Hamiltonian formulations of f(R) gravity and their canonical relationships (2009)
Deruelle, Nathalie, Sendouda, Yuuiti, Youssef, Ahmed
Various Hamiltonian formulations of f(R) gravity can be found in the literature. Some authors follow the Ostrogradsky treatment of higher derivative theories and introduce as extra variables first...
Anabalon, Andres, Deruelle, Nathalie, Morisawa, Yoshiyuki, Oliva, Julio, Sasaki, Misao, Tempo, David, ...
As is well-known, Kerr-Schild metrics linearize the Einstein tensor. We shall see here that they also simplify the Gauss-Bonnet tensor, which turns out to be only quadratic in the arbitrary...
"Detuned" f(R) gravity and dark energy (2008)
Deruelle, Nathalie, Sasaki, Misao, Sendouda, Yuuiti
In gravity theories derived from a f(R) Lagrangian, matter is usually supposed to be minimally coupled to the metric, which hence defines a ``Jordan frame.'' However, since the field equations are...
Long-Wavelength Iteration Scheme and Scalar-Tensor Gravity (2007)
G. L. Comer, Nathalie Deruelle, Centre National, Recherche Scientifique, ...
Inhomogeneous and anisotropic cosmologies are modeled withing the framework of scalar-tensor gravity theories. The inhomogeneities are calculated to third-order in the so-called long-wavelength...
Cosmological Perturbations seeded by Topological Defects: Setting the Initial Conditions (2007)
Nathalie Deruelle, David Langlois, Jean-Philippe Uzan
We consider a perfectly homogeneous and isotropic universe which undergoes a sudden phase transition. If the transition produces topological defects, which we assume, perturbations in the geometry...
Nathalie Deruelle, Joseph Katz, Short Title
1 Abstract. We show the relation between Traschen's integral equations and the energy, and "position of the centre of mass", of the matter perturbations in a Robertson-Walker...
Junction Conditions in f(R) Theories of Gravity (2007)
Deruelle, Nathalie, Sasaki, Misao, Sendouda, Yuuiti
Taking advantage of the conformal equivalence of f(R) theories of gravity with General Relativity coupled to a scalar field we generalize the Israel junction conditions for this class of theories by...
Cosmic microwave background anisotropies seeded by incoherent sources (2007)
Riazuelo, Alain, Deruelle, Nathalie
The cosmic microwave background anisotropies produced by active seeds, such as topological defects, have been computed recently for a variety of models by a number of authors. In this paper we show...
Low energy effective gravitational equations on a Gauss-Bonnet brane (2006)
Kobayashi, Tsutomu, Shiromizu, Tetsuya, Deruelle, Nathalie
We present effective gravitational equations at low energies in a $Z_2$-symmetric braneworld with the Gauss-Bonnet term. Our derivation is based on the geometrical projection approach, and we solve...
Comments on conformal masses, asymptotics backgrounds and conservation laws (2005)
Deruelle, Nathalie, Katz, Joseph
The "conformal mass prescriptions" were used recently to calculate the mass of spacetimes in higher dimensional and higher curvature theories of gravity. These definitions are closely related to...
Mass and angular momenta of Kerr-anti-de Sitter spacetimes (2005)
We briefly review how to compute the mass and angular momenta of rotating, asymptotically anti-de Sitter spacetimes in Einstein-Gauss-Bonnet theory of gravity using superpotentials derived from...
Mass and angular momenta of Kerr anti-de Sitter spacetimes in Einstein-Gauss-Bonnet theory (2004)
Deruelle, Nathalie, Morisawa, Yoshiyuki
We compute the mass and angular momenta of rotating anti-de Sitter spacetimes in Einstein-Gauss-Bonnet theory of gravity using a superpotential derived from standard Noether identities. The...
On the mass of a Kerr-anti-de Sitter spacetime in D dimensions (2004)
Deruelle, Nathalie, Katz, Joseph
We show how to compute the mass of a Kerr-anti-de Sitter spacetime with respect to the anti-de Sitter background in any dimension, using a superpotential which has been derived from standard Noether...
Bouncing universes and their perturbations : a simple model revisited (2004)
Deruelle, Nathalie, Streich, Andreas
We reconsider the toy model studied in [1] of a spatially closed Friedmann-Lemaitre universe, driven by a massive scalar field, which deflates quasi-exponentially, bounces and then enters a period of...
Bouncing universes and their perturbations: remarks on a toy model (2004)
Friedmann-Lemaitre universes driven by a scalar field, spatially closed and bouncing, were recently studied by Martin and Peter in [1], with the conclusion that the spectrum of their large scale...
Conserved Charges in Einstein Gauss-Bonnet theory (2003)
Deruelle, Nathalie, Katz, Joseph, Ogushi, Sachiko
Using Noether's identities, we define a superpotential with respect to a background for the Einstein Gauss-Bonnet theory of gravity. As an example, we show that its associated conserved charge yields...
Smooth branes and junction conditions in Einstein Gauss-Bonnet gravity (2003)
Deruelle, Nathalie, Germani, Cristiano
Using "smooth brane" solutions of the field equations, we give an alternative derivation of the junction conditions for a "brane" in a five dimensional "bulk", when gravity is governed by the...
Newton's law on an Einstein "Gauss-Bonnet" brane (2003)
Deruelle, Nathalie, Sasaki, Misao
It is known that Newton's law of gravity holds asymptotically on a flat "brane" embedded in an anti-de Sitter "bulk" ; this was shown not only when gravity in the bulk is described by Einstein's...
On the quasi-linearity of the Einstein- "Gauss-Bonnet" gravity field equations (2003)
Deruelle, Nathalie, Madore, John
We review some properties of the Einstein-"Gauss-Bonnet" equations for gravity--also called the Einstein-Lanczos equations in five and six dimensions, and the Lovelock equations in higher dimensions....
Cosmological perturbations of an expanding brane in an anti-de Sitter bulk: a short review (2003)
Since the Randall-Sundrum 1999 papers, braneworlds have been a favourite playground to test string inspired cosmological models. The subject has developped into two main directions : elaborating more...
Linearized gravity on branes: from Newton's law to cosmological perturbations (2003)
We review here how Newton's law can be approximately recovered in the simple, "paradigmatic", case of a flat $Z_2$-symmetric brane in a 5-D anti-de Sitter bulk. We then comment on the difficulties...
Stars on branes: the view from the brane (2001)
We consider spherically symmetric matter configurations on a four dimensional "brane" embedded in a five dimensional $Z_2$-symmetric "bulk". We write the junction conditions between the interior and...
On linearized gravity in the Randall-Sundrum scenario (2001)
Deruelle, Nathalie, Dolezel, Tomas
In the literature about the Randall-Sundrum scenario one finds on one hand that there exist (small) corrections to Newton's law of gravity on the brane, and on another that the exact (and henceforth...
Deruelle, Nathalie, Katz, Joseph
We consider the four dimensional discontinuity generated by two identical pieces of a five dimensional space pasted along their edge (that is a "brane" in a "$Z_2$-symmetric" "bulk"). Using a four...
Perturbations of brane worlds (2000)
Deruelle, Nathalie, Dolezel, Tomas, Katz, Joseph
We consider cosmological models where the universe, governed by Einstein's equations, is a piece of a five dimensional double-sided anti-de Sitter spacetime (that is, a "$Z_2$-symmetric bulk") with...
Slowly rotating voids in cosmology (2000)
Dolezel, Tomas, Bicak, Jiri, Deruelle, Nathalie
We consider a spacetime consisting of an empty void separated from an almost Friedmann-Lema\^\i tre-Robertson-Walker (FLRW) dust universe by a spherically symmetric, slowly rotating shell which is...
Cosmic microwave background anisotropies seeded by incoherent sources (2000)
Riazuelo, Alain, Deruelle, Nathalie
The cosmic microwave background anisotropies produced by active seeds, such as topological defects, have been computed recently for a variety of models by a number of authors. In this paper we show...
Brane versus shell cosmologies in Einstein and Einstein-Gauss-Bonnet theories (2000)
Deruelle, Nathalie, Dolezel, Tomas
We first illustrate on a simple example how, in existing brane cosmological models, the connection of a 'bulk' region to its mirror image creates matter on the 'brane'. Next, we present a...
Topological Defects and CMB anisotropies : Are the predictions reliable ? (1999)
Riazuelo, Alain, Deruelle, Nathalie, Peter, Patrick
We consider a network of topological defects which can partly decay into neutrinos, photons, baryons, or Cold Dark Matter. We find that the degree-scale amplitude of the cosmic microwave background...
Uzan, Jean-Philippe, Deruelle, Nathalie, Riazuelo, Alain
We consider a perfectly homogeneous, isotropic and spatially flat universe which undergoes a sudden phase transition producing topological defects. We assume that these defects form a coherent...
Conservation Laws and Cosmological Perturbations in Curved Universes (1998)
Uzan, Jean-Philippe, Deruelle, Nathalie, Turok, Neil
When working in synchronous gauges, pseudo-tensor conservation laws are often used to set the initial conditions for cosmological scalar perturbations, when those are generated by topological defects...
Conservation Laws for Cosmological Perurbations (1998)
Deruelle, Nathalie, Uzan, Jean-Philippe
We briefly recall the problem of defining conserved quantities such as energy in general relativity, and the solution by introducing a symmetric background. We apply the general formalism to...
Cosmological Perturbations seeded by Topological Defects: Setting the Initial Conditions (1997)
Deruelle, Nathalie, Langlois, David, Uzan, Jean-Philippe
We consider a perfectly homogeneous and isotropic universe which undergoes a sudden phase transition. If the transition produces topological defects, which we assume, perturbations in the geometry...
Integral Constraints On cosmological Perturbations and their Energy (1996)
Deruelle, Nathalie, Katz, Joseph, Uzan, Jean-Philippe
We show the relation between Traschen's integral equations and the energy, and ``position of the centre of mass'', of the matter perturbations in a Robertson-Walker spacetime. When the perturbations...
Long-wavelength iteration scheme and scalar-tensor gravity (1996)
Comer, G. L., Deruelle, Nathalie, Langlois, David
Inhomogeneous and anisotropic cosmologies are modeled withing the framework of scalar-tensor gravity theories. The inhomogeneities are calculated to third-order in the so-called long-wavelength...
On matching conditions for cosmological perturbations (1995)
Deruelle, Nathalie, Mukhanov, V. F.
We derive the matching conditions for cosmological perturbations in a Friedmann Universe where the equation of state undergoes a sharp jump, for instance as a result of a phase transition. The...
Conditions for inflation in an initially inhomogeneous universe (1994)
Deruelle, Nathalie, Goldwirth, Dalia S.
Using a long wavelength iteration scheme to solve Einstein's equations near the Big-Bang singularity of a universe driven by a massive scalar field, we find how big initial quasi-isotropic...
25ème École d'été de Physique des Particules, v.1 (1994)
Bouquet, Alain, Derendinger, Jean-Pierre, Deruelle, Nathalie
On The Quantisation Of Perturbations In Inflation (1991)
Nathalie Deruelle, Carsten Gundlach, David Polarski
The theory of gauge-invariant scalar perturbations in chaotic inflation is briefly reviewed. We clarify a problem related to their quantisation, pertinent to any inflationary model. 1 1. Introduction...