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

Tuesday Jun 3, 2025, 10:00 AM → 6:00 PM Europe/Paris

Salle de conférence du Château de Meudon (LUX, Observatoire de Paris)

 

 

 

 

 

 

 

 

 

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 mardi 3 juin 2025 à Meudon.   Cette journée comprendra des conférences couvrant divers aspects de la relativité générale et de ses modifications — un plan préliminaire sera bientôt disponible. 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 : TBA

[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 Tuesday, June 3rd 2025 in Meudon.   The one-day event will feature lectures covering various aspects of general relativity and its modifications — a preliminary plan will be available soon. 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: TBA

 

Speakers:

• Carlo Heissenberg (IPhT)
• Jibril Ben Achour (ENS Lyon)
• Christopher Aykroyd (LTE)
• Etienne Ligout (APC)

10:00 AM → 10:30 AM Welcome

10:30 AM → 12:30 PM TBA

Speaker: Carlo Heissenberg (IPhT, CEA Saclay)

12:30 PM → 2:00 PM Lunch

2:00 PM → 4:00 PM TBA

Speaker: Jibril Ben Achour (ENS Lyon)

4:00 PM → 4:30 PM Break

4:30 PM → 5:15 PM TBA

Speaker: Christopher Aykroyd (LTE, Observatoire de Paris)

5:15 PM → 6:00 PM Innermost stable circular orbit of compact binaries at the fourth post-Newtonian order

We compute by means of post-Newtonian (PN) methods the innermost stable circular orbit (ISCO) of compact binaries. Two methods are used, with equivalent results: one based on the equations of motion in harmonic coordinates and one on the Hamiltonian formalism in ADM coordinates. The ISCO is deduced from an invariant stability criterion, extending the 3PN criterion of Blanchet and Iyer (2003) to the 4PN order. The heart of the derivation of this 4PN criterion is the study of the perturbation of the tail integrals appearing in the dynamics, which are non-local in time. We also explicitly show that the 4PN Lagrangian and 4PN Hamiltonian intermediate results are equivalent by deriving the relation between harmonic and ADM coordinates.

Speaker: Etienne Ligout (APC)