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

Contribution List

1. Gravitational Waveforms, Soft Theorems and Scattering Amplitudes

Carlo Heissenberg (IPhT, CEA Saclay)

6/3/25, 10:15 AM

Scattering amplitudes provide a convenient strategy to calculate gravitational-wave observables characterizing compact binaries in the weak-field or post-Minkowskian (PM) regime, when the two objects remain far away from each other. Conversely, classical soft theorems encode exact information about the dynamics of such systems and do not rely on the PM expansion, while of course restricting to...

3. Non-conservative Hamiltonian perturbation methods for post-Newtonian binary dynamics at 2.5PN

Christopher Aykroyd (LTE, Observatoire de Paris)

6/3/25, 12:15 PM

Non-conservative processes, such as gravitational radiation in
compact binaries, are inherently challenging to describe within traditional
action principles. To address this limitation, a useful strategy is to embed
the system into a higher dimensional manifold, which allows the variational
principle to be reframed via initial (causal) conditions. This approach has
been explored both in...

2. Exact solutions in DHOST gravity: From black holes to radiative spacetime

Jibril Ben Achour (ENS Lyon)

6/3/25, 2:15 PM

Exact solutions are crucial in our understanding of the gravitational field both for black hole and gravitational waves. In this talk, I will review the efforts in constructing exact solutions in modified gravity, focusing on the case of Degenerate Higher Order Scalar Tensor (DHOST) theories. I will underline the limitations we face so far to explore and organize the solution space of these...

4. Innermost stable circular orbit of compact binaries at the fourth post-Newtonian order

Etienne Ligout (APC)

6/3/25, 4:45 PM

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)...