D. A. Steer
A5007345351- Pulsars and Gravitational Waves Research
- Cosmology and Gravitation Theories
- Gamma-ray bursts and supernovae
- Black Holes and Theoretical Physics
- Geophysics and Gravity Measurements
- Astrophysical Phenomena and Observations
- Galaxies: Formation, Evolution, Phenomena
- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- High-pressure geophysics and materials
- Astronomy and Astrophysical Research
- Atomic and Subatomic Physics Research
- Cold Atom Physics and Bose-Einstein Condensates
- Particle physics theoretical and experimental studies
- Quantum Chromodynamics and Particle Interactions
- Dark Matter and Cosmic Phenomena
- Noncommutative and Quantum Gravity Theories
- Nonlinear Waves and Solitons
- Physics of Superconductivity and Magnetism
- Geophysics and Sensor Technology
- Magnetic confinement fusion research
- Seismic Waves and Analysis
- High-Energy Particle Collisions Research
- Superconducting Materials and Applications
- Quantum, superfluid, helium dynamics
Laboratoire AstroParticule et Cosmologie
2013-2025
Université Paris Cité
2015-2025
Laboratoire de Physique de l'ENS
2024-2025
École Normale Supérieure - PSL
2024-2025
Centre National de la Recherche Scientifique
2014-2024
Sorbonne Paris Cité
2014-2021
Commissariat à l'Énergie Atomique et aux Énergies Alternatives
2002-2021
Délégation Paris 7
2011-2021
Institut d'Astrophysique de Paris
2014-2015
Université Savoie Mont Blanc
2015
We determine the most general scalar field theories which have an action that depends on derivatives of order two or less, and equations motion stay second lower flat space-time. show those can all be obtained from linear combinations Lagrangians made by multiplying a particular form Galileon Lagrangian arbitrary function its first derivatives. also obtain curved space-time extensions for both metric field. This provide extension, under condition order, k-essence, Galileons, k-Mouflage as...
Cosmic string networks offer one of the best prospects for detection cosmological gravitational waves (GWs). The combined incoherent GW emission a large number loops leads to stochastic background (SGWB), which encodes properties network. In this paper we analyze ability Laser Interferometer Space Antenna (LISA) measure background, considering leading models networks. We find that LISA will be able probe cosmic strings with tensions Gμ ≳ (10−17), improving by about 6 orders magnitude current...
The observation of binary neutron star merger GW170817, along with its optical counterpart, provided the first constraint on Hubble constant ${H}_{0}$ using gravitational wave standard sirens. When no counterpart is identified, a galaxy catalog can be used to provide necessary redshift information. However, true host might not contained in which complete out limit gravitational-wave detectability. These electromagnetic and selection effects must accounted for. We describe implement method...
The European Pulsar Timing Array (EPTA) and Indian (InPTA) collaborations have measured a low-frequency common signal in the combination of their second first data releases respectively, with correlation properties gravitational wave background (GWB). Such may its origin number physical processes including cosmic population inspiralling supermassive black hole binaries (SMBHBs); inflation, phase transitions, strings tensor mode generation by non-linear evolution scalar perturbations early...
The last years have witnessed remarkable advances in our understanding of the emergence and consequences topological constraints biological soft matter. Examples are abundant relation to (bio)polymeric systems range from characterization knots single polymers proteins that whole chromosomes polymer melts. At same time, considerable been made description interplay between physical properties complex fluids, with development techniques now allow researchers control formation interaction...
We study cosmological perturbations in general inflation models with multiple scalar fields and arbitrary kinetic terms, special emphasis on the multifield extension of Dirac-Born-Infeld (DBI) inflation. compute second-order action governing dynamics linear most case. Specializing to DBI inflation, we show that adiabatic entropy modes propagate a common effective sound speed are thus amplified at horizon crossing. In small limit, find amplitude is much higher than modes. also derive, case,...
We study Dirac-Born-Infeld inflation models with multiple scalar fields. show that the adiabatic and entropy modes propagate a common effective sound speed are thus amplified at horizon crossing. In small limit, we find amplitude of is much higher than modes. this could strongly affect observable curvature power spectrum as well non-Gaussianities, although their shape remains in single-field case.
We review different constructions of Galileon theories in both flat and curved space, for single scalar field models as well multi-field models.Our main emphasis is on the formal mathematical properties these their construction.
We consider Galileon models on curved spacetime, as well the counterterms introduced to maintain second-order nature of field equations these when both metric and scalar are made dynamical. Working in a gauge-invariant framework, we first show how all third-order time derivatives appearing equations---both scalar---of model or one defined by given counterterm can be eliminated leave which contain at most scalar. The same is shown hold for arbitrary linear combinations such models, their...
Knowledge of the shape mass spectrum compact objects can be used to help break degeneracy between and redshift gravitational wave (GW) sources thus infer cosmological parameters in absence measurements obtained from electromagnetic observations. In this paper, we study extensively different aspects approach, including its computational limits achievable accuracy. Focusing on ground-based detectors with current future sensitivities, first perform analysis an extensive set simulated data using...
We study the stochastic gravitational wave background (SGWB) produced by freely decaying vortical turbulence in early Universe. thoroughly investigate time correlation of velocity field, and hence anisotropic stresses producing waves. With hydrodynamical simulations, we show that unequal function (UETC) Fourier components field is Gaussian difference, as predicted "sweeping" decorrelation model. introduce a model can be extended to wavelengths around integral scale flow. Supplemented with...
Abstract We outline the “dark siren” galaxy catalog method for cosmological inference using gravitational wave (GW) standard sirens, clarifying some common misconceptions in implementation of this method. When a confident transient electromagnetic counterpart to GW event is unavailable, identification unique host general challenging. Instead, as originally proposed by Schutz, one can consult and implement dark siren statistical approach incorporating all potential galaxies within...
Gravitational wave (GW) sources at cosmological distances can be used to probe the expansion rate of Universe. GWs directly provide a distance estimation source but no direct information on its redshift. The optimal scenario obtain redshift is through identification an electromagnetic (EM) counterpart and host galaxy. With almost 100 GW detected without EM counterparts (dark sirens), it becoming crucial have statistical techniques able perform studies in absence emission. Currently, only two...
We set up cosmological perturbation theory and study the implications of so-called ``generalized Galileon'' developed in \cite{Deffayet:2011gz,horndeski}. This is most general scalar field whose Lagrangian contains derivatives to second order while keeping equations motion, as sub-cases $k$-inflation, $G$-inflation many other models. calculate power spectrum primordial curvature perturbation, finding a modification usual consistency relation tensor-to-scalar ratio $k$-inflation or perfect...
The direct detection of gravitational waves by the LIGO/Virgo Collaboration has opened a new window with which to measure cosmological parameters such as Hubble constant ${H}_{0}$, and also probe general relativity on large scales. In this paper we present phenomenological approach, together its inferential implementation, for measuring deviations from (GR) scales concurrently determination ${H}_{0}$. We consider (GWs) propagating in an expanding homogeneous isotropic background, but...
Gravitational wave (GW) standard sirens are well-established probes with which one can measure cosmological parameters, and complementary to other like the cosmic microwave background or supernovae candles. Here we focus on dark GW sirens, specifically binary black holes (BBHs) for there is only data. Our approach relies assumption of a source frame mass model BBH distribution, consider four models that representative population observed so far. In addition inferring use test modified...
The Laser Interferometer Space Antenna (LISA) has two scientific objectives of cosmological focus: to probe the expansion rate universe, and understand stochastic gravitational-wave backgrounds their implications for early universe particle physics, from MeV Planck scale. However, range potential applications gravitational wave observations extends well beyond these objectives. This publication presents a summary state art in LISA cosmology, theory methods, identifies new opportunities use...
We compare the standard single scalar field inflationary predictions with those of an phase driven by a tachyon field. A slow-roll formalism is defined for inflation, and we derive spectra tensor perturbations as well consistency relations. At lowest order inflation are shown to be same. Higher deviations present their observational relevance discussed. then study some typical potentials, discuss consequences them recent data. All models predict negative very small running spectral index,...
We account for particle emission and gravitational radiation from cosmic string loops to determine their effect on the loop distribution observational signatures of strings. The is that number density no longer scales. This results in a high-frequency cutoff stochastic wave background, but we show expected outside range current planned detectors. Particle also produces diffuse gamma-ray background sensitive presence kinks cusps loops. However, both cusps, with mild assumptions about physics...
We search for a stochastic gravitational wave background (SGWB) generated by network of cosmic strings using six millisecond pulsars from Data Release 2 (DR2) the European Pulsar Timing Array (EPTA). perform Bayesian analysis considering two models string loops, and compare it to simple power-law model which is expected population supermassive black hole binaries. Our main strong assumption that previously reported common red noise process SGWB. find one-parameter slightly favored over...
We study the dynamics of Nambu-Goto strings with junctions at which three meet. In particular, we exhibit one simple exact solution and examine process intercommuting two straight in they exchange partners but become joined by a third string. show that there are important kinematical constraints on this process. The cannot occur if meet very large relative velocity. This may have implications for evolution cosmic superstring networks non-Abelian string networks.