A5088222205- Cosmology and Gravitation Theories
- Geophysics and Gravity Measurements
- Pulsars and Gravitational Waves Research
- Solar and Space Plasma Dynamics
- Radio Astronomy Observations and Technology
- Computational Physics and Python Applications
- Geomagnetism and Paleomagnetism Studies
- Statistical and numerical algorithms
- Astrophysics and Cosmic Phenomena
- Geological Studies and Exploration
- Galaxies: Formation, Evolution, Phenomena
- Astro and Planetary Science
- Fluid Dynamics and Turbulent Flows
- Dark Matter and Cosmic Phenomena
- Cold Atom Physics and Bose-Einstein Condensates
- Black Holes and Theoretical Physics
- Geophysics and Sensor Technology
- Astronomy and Astrophysical Research
- Particle physics theoretical and experimental studies
- Astrophysics and Star Formation Studies
- Planetary Science and Exploration
University of Geneva
2022-2024
Université Paris Cité
2020-2023
Centre National de la Recherche Scientifique
2021-2023
Ilia State University
2018-2023
Laboratoire AstroParticule et Cosmologie
2021-2023
Agence Parisienne du Climat
2021
University of Colorado Boulder
2017-2020
Laboratory for Atmospheric and Space Physics
2017-2020
University of Colorado System
2020
Abastumani Astrophysical Observatory
2018-2019
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...
We compute the gravitational wave (GW) spectrum sourced by sound waves produced during a first-order phase transition in radiation-dominated epoch. The correlator of velocity field perturbations is evaluated accordance with shell model. In our derivation we include effects expansion Universe, which are relevant particular for sourcing processes whose time duration comparable Hubble time. Our results show causal growth GW at small frequencies,...
Abstract The Lunar Gravitational-wave Antenna (LGWA) is a proposed array of next-generation inertial sensors to monitor the response Moon gravitational waves (GWs). Given size and expected noise produced by lunar seismic background, LGWA would be able observe GWs from about 1 mHz Hz. This make missing link between space-borne detectors like LISA with peak sensitivities around few millihertz future terrestrial Einstein Telescope or Cosmic Explorer. In this article, we provide first...
We perform direct numerical simulations of magnetohydrodynamic turbulence in the early universe and numerically compute resulting stochastic background gravitational waves relic magnetic fields. These do not make simplifying assumptions earlier analytic work. If is assumed to have an energy-carrying scale that about a hundredth Hubble radius at time generation, as expected first-order phase transition, peak wave power will be mHz frequency range for signal produced electroweak scale. The...
We present new simulations of decaying hydromagnetic turbulence for a relativistic equation state relevant to the early universe. compare helical and nonhelical cases either with kinetically or magnetically dominated initial fields. Both kinetic magnetic helicities lead maximally fields after some time, but different temporal decay laws. are universe, although no mechanisms have yet been identified that produce helicity strengths comparable big bang nucleosynthesis limit at scales Hubble...
The NANOGrav Collaboration has recently reported evidence for the existence of a stochastic gravitational wave background in 1--100 nHz frequency range. We argue that such could have been produced by magnetohydrodynamic (MHD) turbulence at QCD scale. From measurement, one can infer magnetic field parameters: comoving strength close to microGauss and correlation length 10% Hubble radius phase transition epoch. point out turbulent decay nonhelical with parameters leads recombination epoch,...
The NANOGrav, Parkes, European, and International Pulsar Timing Array (PTA) Collaborations have reported evidence for a common-spectrum process that can potentially correspond to stochastic gravitational wave background (SGWB) in the 1--100 nHz frequency range. We consider scenario which this signal is produced by magnetohydrodynamic (MHD) turbulence early Universe, induced nonhelical primordial magnetic field at energy scale corresponding quark confinement phase transition. perform MHD...
Abstract We develop a tool for the analysis of stochastic gravitational wave backgrounds from cosmological first-order phase transitions with LISA: we initiate template databank these signals, prototype their searches, and forecast reconstruction. The templates encompass signals sourced by bubble collisions, sound waves turbulence. Accounting Galactic extra-Galactic foregrounds, region parameter space that LISA will reconstruct better than ∼ 10% accuracy, if certain experimental theoretical...
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...
Abstract We use direct numerical simulations of decaying primordial hydromagnetic turbulence with helicity to compute the resulting gravitational wave (GW) production and its degree circular polarization. The is sourced by magnetic fields that are either initially present or driven an electromotive force applied for a short duration, given as fraction one Hubble time. In both types simulations, we find clear dependence polarization GWs on fractional turbulent source. low frequency tail below...
We review the conservation laws of magnetohydrodynamics (MHD) in an expanding homogeneous and isotropic Universe that can be applied to study early physics during epoch radiation domination. The for a conducting perfect fluid with relativistic bulk velocities background are presented, extending previous results apply limit subrelativistic motion. Furthermore, it is shown presents new corrections have not been considered work. Imperfect fluids briefly described but their detailed included...
We show that in decaying hydromagnetic turbulence with initial kinetic helicity, a weak magnetic field eventually becomes fully helical. The sign of helicity is opposite to the - regardless whether or not was undergoes inverse cascading energy approximately like t^{-1/2}. This even slower than helical case, where it decays t^{-2/3}. In this parameter range, product and correlation length raised certain power slightly larger unity, constant. scaling persists over long time scales. At very...
We study the gravitational wave (GW) signal sourced by primordial turbulence that is assumed to be present at cosmological phase transitions like electroweak and quantum chromodynamics transitions. consider various models of turbulence, such as those with without helicity, purely hydrodynamical induced fluid motions, magnetohydrodynamic whose energy can dominated either kinetic or magnetic energy, depending on nature turbulence. also circularly polarized GWs generated parity violating...
The Lunar Gravitational-wave Antenna (LGWA) is a proposed array of next-generation inertial sensors to monitor the response Moon gravitational waves (GWs). Given size and expected noise produced by lunar seismic background, LGWA would be able observe GWs from about 1 mHz Hz. This make missing link between space-borne detectors like LISA with peak sensitivities around few millihertz future terrestrial Einstein Telescope or Cosmic Explorer. In this article, we provide first comprehensive...
Hydromagnetic turbulence produced during phase transitions in the early universe can be a powerful source of stochastic gravitational waves (GWs). GWs modelled by linearised spatial part Einstein equations sourced Reynolds and Maxwell stresses. We have implemented two different GW solvers into {\sc Pencil Code} -- code which uses third order timestep sixth finite differences. Using direct numerical integration equations, we study appearance degradation amplitude at highest wavenumbers,...
We perform direct numerical simulations to compute the net circular polarization of gravitational waves from helical (chiral) turbulent sources in early Universe for a variety initial conditions, including driven (stationary) and decaying turbulence. investigate resulting wave signal assuming different geneses such as magnetically or kinetically cases. Under realistic physical conditions we numerically number-dependent degree waves. find that spectral strongly depends on conditions. The peak...
Gradient- and curl-type or E- B-type polarizations have been routinely analyzed to study the physics contributing cosmic microwave background polarization galactic foregrounds. They characterize parity-even parity-odd properties of underlying physical mechanisms, for example hydromagnetic turbulence in case dust polarization. Here we spectral correlation functions characterizing parts linear homogeneous inhomogeneous show that only helical can give rise a signal. We also nonhelical suggest...
We develop a tool for the analysis of stochastic gravitational wave backgrounds from cosmological first-order phase transitions with LISA: we initiate template databank these signals, prototype their searches, and forecast reconstruction. The templates encompass signals sourced by bubble collisions, sound waves turbulence. Accounting Galactic extra-Galactic foregrounds, region parameter space that LISA will reconstruct better than $\sim 10\,\%$ accuracy, if certain experimental theoretical...
We study the propagation of cosmological gravitational wave (GW) backgrounds from early radiation era until present day in modified theories gravity. Comparing to general relativity (GR), we effects that gravity parameters, such as GW friction $\alpha_{\rm M}$ and tensor speed excess T}$, have on present-day spectrum. use both WKB estimate, which provides an analytical description but fails at superhorizon scales, numerical simulations allow us go beyond approximation. show a constant T}$...
Abstract Blazar observations point toward the possible presence of magnetic fields over intergalactic scales order up to ∼1 Mpc, with strengths at least ∼10 −16 G. Understanding origin these large-scale is a challenge for modern astrophysics. Here we discuss cosmological scenario, focussing on following questions: (i) How and when was this field generated? (ii) does it evolve during expansion universe? (iii) Are amplitude statistical properties such that they can explain correlation lengths...
We study the generation of gravitational waves (GWs) during a first-order cosmological phase transition (PT) using recently introduced Higgsless approach to numerically evaluate fluid motion induced by PT. present for first time spectra from strong PTs ($\alpha = 0.5$), alongside weak 0.0046$) and intermediate 0.05$) transitions previously considered in literature. test regime applicability stationary source assumption, characteristic sound-shell model, show that it agrees with our numerical...
We study two possible cosmological consequences of a first-order phase transition in the temperature range $1$ GeV to $10^3$ TeV: generation stochastic gravitational wave background (SGWB) within sensitivity Laser Interferometer Space Antenna (LISA) and, simultaneously, primordial magnetic fields that would evolve through Universe's history and could be compatible with lower bound from $\gamma$-ray telescopes on intergalactic (IGMF) at present time. find that, if even small fraction kinetic...
We propose that the recent observations reported by different Pulsar Timing Array (PTA) collaborations (i.e.~IPTA, EPTA, PPTA, and NANOGrav) of a common process over several pulsars could correspond to stochastic gravitational wave background (SGWB) produced turbulent sources in early universe, particular due magnetohydrodynamic (MHD) turbulence induced primordial magnetic fields. I discuss results numerical simulations MHD present an analytical template SGWB validated simulations. use this...