David Langlois
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View article: Neutron stars in degenerate higher-order scalar-tensor theories: Axial perturbations
Neutron stars in degenerate higher-order scalar-tensor theories: Axial perturbations Open
We study the axial (or odd-parity) perturbations of neutron stars in a one-parameter subclass of Degenerate Higher-Order Scalar-tensor (DHOST) theories. After recalling the equilibrium neutron star configurations obtained in a previous wor…
View article: Innermost stable circular orbit of arbitrary-mass compact binaries at fourth post-Newtonian order
Innermost stable circular orbit of arbitrary-mass compact binaries at fourth post-Newtonian order Open
We compute by means of post-Newtonian (PN) methods the innermost stable circular orbit (ISCO) of arbitrary-mass (in particular, comparable-mass) compact binaries. Two methods are used with equivalent results: dynamical perturbation of the …
View article: Axial perturbations of black holes with primary scalar hair
Axial perturbations of black holes with primary scalar hair Open
We study axial perturbations of static black holes with primary hair in a family of degenerate higher-order scalar-tensor (DHOST) theories. These solutions possess a scalar charge, fully independent of the mass, leading to a continuous one…
View article: Degenerate higher-order Maxwell theories in flat space-time
Degenerate higher-order Maxwell theories in flat space-time Open
A bstract We consider, in Minkowski spacetime, higher-order Maxwell Lagrangians with terms quadratic in the derivatives of the field strength tensor, and study their degrees of freedom. Using a 3+1 decomposition of these Lagrangians, we ex…
View article: What Do BERT Word Embeddings Learn about the French Language
What Do BERT Word Embeddings Learn about the French Language Open
Pre-trained word embeddings (for example, BERT-like) have been successfully used in a variety of downstream tasks. However, do all embeddings, obtained from the models of the same architecture, encode information in the same way? Does the …
View article: A Lightweight and Compact Lockable Parallel Spring Enhances the Performance of a Powered Ankle-Foot Prosthesis
A Lightweight and Compact Lockable Parallel Spring Enhances the Performance of a Powered Ankle-Foot Prosthesis Open
Lower-limb amputation has a major impact on locomotion and quality of life. The last few decades have seen the emergence of powered devices aiming at replacing the missing limb and restoring the lost mobility. These devices endeavor to rep…
View article: Degenerate Higher-Order Maxwell Theories in Flat Space-Time
Degenerate Higher-Order Maxwell Theories in Flat Space-Time Open
We consider, in Minkowski spacetime, higher-order Maxwell Lagrangians with terms quadratic in the derivatives of the field strength tensor, and study their degrees of freedom. Using a 3+1 decomposition of these Lagrangians, we extract the …
View article: Classification of generalised higher-order Einstein-Maxwell Lagrangians
Classification of generalised higher-order Einstein-Maxwell Lagrangians Open
A bstract We classify all higher-order generalised Einstein-Maxwell Lagrangians that include terms linear in the curvature tensor and quadratic in the derivatives of the electromagnetic field strength tensor. Using redundancies due to the …
View article: Towards A Neural Machine Translation Proposal to Help Everyday Communication for People with Broca’s Aphasia
Towards A Neural Machine Translation Proposal to Help Everyday Communication for People with Broca’s Aphasia Open
Stroke is among the most common causes of death and disability worldwide. More than 12 million people suffer from a stroke every year, 4 million of whom develop an aphasia. Aphasia is a language disorder that affects up to 0.6% of the glob…
View article: Numerical computation of quasinormal modes in the first-order approach to black hole perturbations in modified gravity
Numerical computation of quasinormal modes in the first-order approach to black hole perturbations in modified gravity Open
We present a novel approach to the numerical computation of quasi-normal modes, based on the first-order (in radial derivative) formulation of the equations of motion and using a matrix version of the continued fraction method. This numeri…
View article: Axial perturbations of black holes in scalar-tensor gravity: near-horizon behaviour
Axial perturbations of black holes in scalar-tensor gravity: near-horizon behaviour Open
We consider axial (or odd-parity) perturbations of non-spinning hairy black holes (BH) in shift-symmetric DHOST (Degenerate Higher-Order Scalar-Tensor) theories, including terms quartic and cubic in second derivatives of the scalar field. …
View article: Development of an Integrated Powered Hip and Microprocessor-Controlled Knee for a Hip–Knee–Ankle–Foot Prosthesis
Development of an Integrated Powered Hip and Microprocessor-Controlled Knee for a Hip–Knee–Ankle–Foot Prosthesis Open
Hip–knee–ankle–foot prostheses (HKAF) are full lower-limb devices for people with hip amputations that enable individuals to regain their mobility and move freely within their chosen environment. HKAFs typically have high rejection rates a…
View article: Axial perturbations of black holes in scalar-tensor gravity: near-horizon behaviour
Axial perturbations of black holes in scalar-tensor gravity: near-horizon behaviour Open
We consider axial (or odd-parity) perturbations of non-spinning hairy black holes (BH) in shift-symmetric DHOST (Degenerate Higher-Order Scalar-Tensor) theories, including terms quartic and cubic in second derivatives of the scalar field. …
View article: Neutron stars in degenerate higher-order scalar-tensor theories
Neutron stars in degenerate higher-order scalar-tensor theories Open
We study neutron star configurations in a simple shift-symmetric subfamily of\ndegenerate higher-order scalar-tensor (DHOST) theories, whose deviations from\nGeneral Relativity (GR) are characterized by a single parameter. We compute the\n…
View article: Language rehabilitation of people with BROCA aphasia using deep neural machine translation
Language rehabilitation of people with BROCA aphasia using deep neural machine translation Open
International audience
View article: Linear perturbations of Einstein-Gauss-Bonnet black holes
Linear perturbations of Einstein-Gauss-Bonnet black holes Open
We study linear perturbations about non rotating black hole solutions in scalar-tensor theories, more specifically Horndeski theories. We consider two particular theories that admit known hairy black hole solutions. The first one, Einstein…
View article: On the effective metric of axial black hole perturbations in DHOST gravity
On the effective metric of axial black hole perturbations in DHOST gravity Open
We study axial (or odd-parity) perturbations about static and spherically symmetric hairy black hole (BH) solutions in shift-symmetric DHOST (Degenerate Higher-Order Scalar-Tensor) theories. We first extend to the family of DHOST theories …
View article: Black hole perturbations in modified gravity
Black hole perturbations in modified gravity Open
We study the linear perturbations about nonrotating black holes in the context of degenerate higher-order scalar-tensor (DHOST) theories, using a systematic approach that extracts the asymptotic behaviour of perturbations (at spatial infin…
View article: Asymptotics of linear differential systems and application to quasinormal modes of nonrotating black holes
Asymptotics of linear differential systems and application to quasinormal modes of nonrotating black holes Open
The traditional approach to perturbations of nonrotating black holes in\nGeneral Relativity uses the reformulation of the equations of motion into a\nradial second-order Schr\\"odinger-like equation, whose asymptotic solutions are\nelement…
View article: Quadratic degenerate higher-order scalar-tensor theories revisited
Quadratic degenerate higher-order scalar-tensor theories revisited Open
We present a novel and remarkably simple formulation of degenerate\nhigher-order scalar-tensor (DHOST) theories whose Lagrangian is quadratic in\nsecond derivatives of some scalar field. Using disformal transformations of the\nmetric, we i…
View article: Asymptotics of linear differential systems and application to quasi-normal modes of nonrotating black holes
Asymptotics of linear differential systems and application to quasi-normal modes of nonrotating black holes Open
The traditional approach to perturbations of nonrotating black holes in General Relativity uses the reformulation of the equations of motion into a radial second-order Schrödinger-like equation, whose asymptotic solutions are elementary. I…
View article: Late-time cosmological evolution in degenerate higher-order scalar-tensor models
Late-time cosmological evolution in degenerate higher-order scalar-tensor models Open
We study the late cosmological evolution, from the nonrelativistic matter\ndominated era to the dark energy era, in modified gravity models described by\nDegenerate Higher-Order Scalar-Tensor (DHOST) theories. They represent the most\ngene…
View article: Perturbations of a rotating black hole in DHOST theories
Perturbations of a rotating black hole in DHOST theories Open
We study linear perturbations of a rotating black hole solution that has been\nrecently discovered in degenerate higher-order scalar-tensor (DHOST) theories.\nWe find a parametrization which permits the explicit resolution of the scalar\np…
View article: Summarizing videos into a target language: Methodology, architectures and evaluation
Summarizing videos into a target language: Methodology, architectures and evaluation Open
The aim of the work is to report the results of the Chist-Era project AMIS (Access Multilingual Information opinionS). The purpose of AMIS is to answer the following question: How to make the information in a foreign language accessible fo…
View article: Machine Translation on a parallel Code-Switched Corpus
Machine Translation on a parallel Code-Switched Corpus Open
International audience
View article: Cosmological evolution in DHOST theories
Cosmological evolution in DHOST theories Open
In the context of Degenerate Higher-Order Scalar-Tensor (DHOST) theories, we study cosmological solutions and their stability properties. In particular, we explicitly illustrate the crucial role of degeneracy by showing how the higher orde…
View article: Dark energy and modified gravity in degenerate higher-order scalar–tensor (DHOST) theories: A review
Dark energy and modified gravity in degenerate higher-order scalar–tensor (DHOST) theories: A review Open
This paper reviews scalar–tensor theories characterized by a Lagrangian that, despite the presence of second-order derivatives, contains a single scalar degree of freedom. These theories, known as Degenerate Higher-Order Scalar–Tensor (DHO…