Rencontre commune des groupes de travail "Cosmologie" et “Tests de la relativité générale et théories alternatives” du GdR Ondes Gravitationnelles

Liste des contributions

6. Gravitational waveforms for compact binaries in Einstein-Aether theory

20/06/2022 09:35

We use the post-Minkowskian approach to analyze the Einstein-Aether(AE)/Khronometric theories of gravity. These theories add to the spacetime metric a long-range "aether" vector field, constrained to have unit norm. We constrain one of the four free parameters of the theory to guarantee that light and tensor gravitational waves propagate at the same speed, as seen in the multimessenger event...

3. Constraining spontaneous black hole scalarization with gravitational waves

20/06/2022 10:00

Certain scalar-tensor theories remain viable despite stringent observational constraints from the Solar System due to a Z_2 symmetry that keeps the scalar field dormant in the weak-field regime. However, extreme-gravity environments can trigger a phase transition that promotes a spontaneous growth of the scalar field around compact objects like black holes and neutron stars. This is the...

13. Metric reconstruction for non-radiative spacetimes

20/06/2022 10:25

Multipole moments are important quantities to characterize spacetimes. In General Relativity, the most general vacuum solution with no incoming radiation is parametrized by two sets of infinite multipole moments. In this talk, we focus on non-radiative spacetimes and provide a characterization thereof in terms of a tower of multipole moments. This tower encodes non-radiative and non-stationary...

11. Schwarzschild-like Smooth Geometries in Supergravity

20/06/2022 10:50

A new approach to solve Einstein equations in higher dimensions will be discussed. It consists in decomposing the equations into several sectors with known integrable structure. I will construct large classes of non-supersymmetric smooth solutions that are asymptotic to four-dimensional Minkowski spacetime with additional compact circles. They are induced by bubbles of spacetime supported by...

8. Primordial gravitational waves from excited states

20/06/2022 11:45

How the stochastic gravitational wave background offers one to probe inflation on small scales has been a subject of active research in recent years. However, most studies focus on one specific aspect: the often called scalar induced gravitational-waves, generated after inflation from large primordial density fluctuations. Yet, the phenomenon that generates these large density fluctuations...

5. Cosmological Master Equations

20/06/2022 12:10

Nearly scale-invariant, Gaussian and adiabatic scalar perturbations from quantum mechanical origin have been extensively tested in cosmology using CMB and LSS data. Effective field theories aim at providing a systematic way to consider extensions to this adiabatic evolution, incorporating the knowledge of unknown physics in a parametrically controlled manner. In order to grasp the implications...

2. Constructing wormholes from black holes

20/06/2022 12:35

TBA

12. Tension en Cosmologie sur la valeur de la constante de Hubble-Lemaître, nouvelle physique ou biais astrophysiques ?

20/06/2022 14:30

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10. The H0 Olympics: a fair ranking of proposed models

20/06/2022 14:55

Despite the remarkable success of the Λ Cold Dark Matter (ΛCDM) cosmological model, a growing discrepancy has emerged between the value of the Hubble constant H0 measured using the local distance ladder and the value inferred using the cosmic microwave background and galaxy surveys. While a vast array of ΛCDM extensions have been proposed to explain these discordant observations, understanding...

7. Current and future constraints on cosmology and modified gravitational-wave friction from binary black holes

20/06/2022 15:20

Gravitational wave (GW) standard sirens are well-established probes with which one can measure cosmological parameters, and are complementary to other probes like the cosmic microwave background or supernovae standard candles. In my talk I will focus on dark GW sirens, specifically binary black holes (BBHs) for which there is only GW data. The approach relies on the assumption of a source...

9. The gravitational wave signal from primordial magnetic fields in the Pulsar Timing Array frequency band

20/06/2022 16:15

The NANOGrav, Parkes, European, and the International pulsar timing array (PTA) collaborations have reported evidence for a common-spectrum process that can potentially correspond to a stochastic gravitational wave background (SGWB) in the 1-100 nHz frequency range. I will present the scenario in which this signal is produced by magnetohydrodynamic (MHD) turbulence in the early universe,...

1. Cosmology prospects with massive black hole binaries in LISA

20/06/2022 16:40

In $\sim 2034$ the Laser Interferometer Space Antenna (LISA) will detect the coalescence of massive black hole binaries (MBHBs) from $10^5$ to $10^7 \rm M_{\odot}$ up to $z\sim10$. The gravitational wave (GWs) signal is expected to be accompanied by an electromagnetic (EM) counterpart, from radio to X-ray, generated by the gas accreting on the binary.
In this talk, I present some recent...

4. Cosmology with LISA standard sirens and their host galaxies

20/06/2022 17:05

LISA is expected to deliver unprecedented information on the gravitational wave sources emitting in the mHz frequency band. Extreme mass-ratio inspirals are amongst the main LISA sources and their parameters will be measured with precision, notably their sky localisation. We show that, using the best-localised events as dark standard sirens in combination with a realistic galaxy catalog, these...