Journée des groupes de travail "Formes d'onde" et “Tests de la relativité générale et théories alternatives” du GdR Ondes Gravitationnelles

mercredi 27 mai 2026, 07:00 → 17:00 Europe/Paris

200/0-Auditorium - Auditorium P. Lehmann (IJCLab)

 

 

 

 

 

 

 

 

 

 

 

Image credits: R. Hurt (Caltech-IPAC) [https://www.ligo.caltech.edu/image/ligo20160211f]

 

 

[FR] La rencontre commune des groupes de travail "Formes d'onde" et "Tests de la relativité générale et théories alternatives" du GdR Ondes Gravitationnelles se déroulera le mercredi 27 mai 2026 à Orsay.   Cette journée comprendra des conférences couvrant divers aspects de la relativité générale et de ses modifications. Ce format conviendra bien aux participants de tous niveaux d'expertise, en particulier aux doctorant.e.s, post-doctorant.e.s et jeunes chercheur.e.s.   La participation est gratuite, mais l'inscription est obligatoire.   Date limite d'inscription : 20 mai, 23:59.

[EN] The joint meeting of the working groups "Waveform" and "Tests of general relativity and alternative theories" of the GdR Gravitational Waves will take place on Wednesday, May 27th 2026 in Orsay.   The one-day event will feature lectures covering various aspects of general relativity and its modifications. This format will be well suited for participants of all levels of expertise, particularly PhD students, postdocs, and young researches.   Participation is free but registration is compulsory.   Deadline for registration: May 20th, 23:59.

 

Speakers:

• Sara Rufrano Aliberti (SSM)
• Tom Colin (LUX)
• Arwa Elhashash (LUX)
• Joffrey Le Grix de la Salle (IJCLab)
• Jacopo Mazza (IJCLab)
• Emeric Seraille (ENS, IAP)
• David Trestini (IAP, LUTh)

09:15 Welcome coffee

1 Analytical solution of spinning and eccentric binary black holes at 2PN

Orateur: Tom Colin (LUX)

IJCLaB.pdf

2 Constants of motion for elliptic orbits: fourth post-Newtonian order and first self-force order

TBA

Orateur: David Trestini (IAP (Sorbonne Université), LUTH (Observatoire de Meudon))

Seminar_GdR__Formes_d_ondes__2026-12.pdf

3 Radiation-Reaction Correction to Scattering Binary Dynamics at Next-to-Leading Post-Newtonian Order

Radiation-reaction force encodes dissipative effects in a binary system emitting gravitational waves. Within the post-Newtonian framework, radiation-reaction terms enter the equations of motion starting at 2.5PN order and affect the system’s dynamics accordingly. These effects can be incorporated as corrections to the quasi-Keplerian orbital parameters in the center-of-mass frame. In this presentation, I will discuss the Lagrange method of variation of constants that we used to determine the radiation-reaction corrections for the quasi-hyperbolic orbit at 3.5PN order.

Orateur: Sara Rufrano Aliberti (Scuola Superiore Meridionale)

Workshop_Paris.pdf

4 Gravitational radiation reaction for compact binary systems at 4.5 post-Newtonian order

Compact binaries are the primary sources of gravitational waves measured by gravitational-wave detectors. In this context, obtaining the equations of motion in different approximation schemes is essential for producing waveform templates with the accuracy required by future detections, constituting a precision test of general relativity.
In this presentation, I derive the gravitational radiation-reaction force on a compact binary system at 4.5PN order, i.e., 2PN orders beyond the leading 2.5PN radiation-reaction term in harmonic coordinates. This result is derived using the 4.5PN gravitational radiation-reaction force in the Burke–Thorne (BT) coordinate system.
This represents a significant improvement, as harmonic coordinates provide a manifestly Lorentz-invariant formulation and offer a much simpler expression compared to the BT coordinates. Moreover, they pave the way for comparisons with other approximation schemes (such as post-Minkowskian or gravitational self-force) at 4.5PN.
Using the harmonic radiation-reaction acceleration, we also derive from first principles the flux-balance laws and the center-of-mass position, in a general frame and up to the 4.5PN order.

Orateur: Emeric Seraille (École Normale Supérieure, IAP)

Emeric Seraille Waveform Orsay.pdf

11:45 Lunch

5 xHam: A Mathematica package for Hamiltonian Analysis

Orateur: Joffrey Le Grix de la Salle

Presentation_xHam_GdR.pdf

6 Beyond circles: stationary axisymmetric black holes and the breaking of circularity

Circularity is an accidental symmetry of the Kerr metric, one that is widely assumed when searching for rotating black hole solutions in modified gravity as well as when constructing models of Kerr mimickers. Though extremely enticing, circularity is often an excessively restrictive assumption, and understanding the consequences of its loss is thus crucially relevant. In this seminar, I wish to present some recent results on the subject: After describing in detail what this symmetry entails, I will show how to construct stationary and axisymmetric spacetimes exhibiting a controlled breaking of circularity; then, I will describe the impact of circularity breaking on the hole’s horizon, focusing in particular on the laws of black hole mechanics. This discussion is thus going to be pertinent for anyone with an interest in compact astrophysical objects and their phenomenology, in general relativity and beyond.

Orateur: Jacopo Mazza (IJCLab)

Non-circular Orsay.pdf

Non-circular Orsay.pptx

7 Time- and frequency-domain waveform models for the gravitational-wave memory effect

The nonlinear gravitational-wave (GW) memory effect is a strong-field gravitational phenomenon that arises from interactions between the GWs with themselves.
This effect manifests as a lasting offset in the GW strain that persists after the passage of a GW.
Although the detection of the memory effect is challenging because the signal is relatively weak (compared to the dominant quadrupolar GWs), it is possible to measure the memory signal in a population of binary-black hole (BBH) mergers with the current GW detectors or from individual BBHs with next-generation space-based GW detectors.
Template-based searches for the memory effect require evaluating the waveforms many times, and they can benefit from fast-to-evaluate and accurate waveform models.
I will present a stand-alone time-domain waveform model for the GW memory effect for nonspinning BBH mergers, which accurately models just the GW signal associated with the memory effect and not other linear or nonlinear GW phenomena.
I will also present independent phenomenological frequency-domain waveforms for the GW memory effect that directly model the signal in the Fourier domain.

Orateur: Arwa Elhashash (LUX, CNRS, Observatoire de Paris)

ArwaElhashash_IJCLab_May27.pdf

15:00 Discussions with coffee