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--- ondesgravitationnelles [2023/02/16 10:47] – daniele.steer
+++ ondesgravitationnelles [2023/03/08 15:08] (current) – daniele.steer
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 La communauté scientifique française est très investie dans la recherche sur les OG, et a porté des avancées majeures sur un large spectre de sujets, allant du développement des détecteurs à l’analyse et l’interprétation des observations astrophysiques, à la modélisation des formes d'ondes gravitationnelles et à l’étude de l’évolution de l’univers sur ses plus grandes échelles, aux tests de la physique fondamentale et de la physique nucléaire.
-Autre que LIGO-Virgo-Kagra (fréquence caractéristique ~Hz), plusieurs grandes experiences sur les ondes gravitationnelles vont continuer à voir le jour, et avec les nouvelles données il y aura d'importants impacts sur la recherche dans les prochaine 10 années.
+Autre que LIGO-Virgo-Kagra (fréquence caractéristique ~10 à 10^3 Hz), plusieurs grandes experiences sur les ondes gravitationnelles vont continuer à voir le jour, et avec les nouvelles données il y aura d'importants impacts sur la recherche dans les prochaine 10 années.
   * LIGO-Virgo-Kagra va commencer son //O4 run// (mai 2023) puis //O5//, et on peut s'attendre à (bien plus) O(1) evennement par jour.
   * A basses fréquences (10-9–10-7 Hz) IPTA va bientot sortir des données de 25 pulsars (si pas deja fait). Nançay Radio Telescope (NRT)
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         * developments to higher PN, with spins and tidal effects, all needed for future detectors especially LISA. Computation of both conservative equations of motion plus effects of gravitational radiation reaction. Computation of waveforms (modes, especially the dominant quadrupole mode 22) and flux balance equations for secular evolution of the binary.
         * Inclusion of eccentricity to higher PN, unbound hyperbolic orbits etc. Relation between unbound and bound (elliptical) orbits including tail effects.
-        * Effective Field theory techniques, amplitudes. These, together with ``classical'' PN approach, will probably develop together. Develop dictionary between the two approaches. [e.g. Asymptotic symmetries: synergy between these symmetries at null infinity and the waveform. Important for non-linear- and spin- memory effects + tails. ]
+        * Effective Field theory techniques, amplitudes. These, together with ``classical'' PN approach, will probably develop together. Develop dictionary between the two approaches. [e.g. Analysis of asymptotic symmetries: synergy between these symmetries at null infinity and the waveform. Important for non-linear- and spin- memory effects + tails. ]
         * Effective one body: under-developed in France, but crucial to match inspiral to ringdown waveforms and for practical implementation of data analysis.
         * Numerical relativity. Tremendous progress over the last decades. A field which is under-developed in France. Connection with the community working of neutron star equations of state.
-        * Quasinormal modes to higher (second) order: recent developments to help the matching?
+        * Quasinormal modes to higher (second) order: more accurate prediction of the ringdown phase following binary black hole mergers and future tests of the black hole no-hair theorem of general relativity.
-        *  Recent progress on the gravitational self force problem for compact binaries, now solved numerically to second order in the mass ratio. Analytic expressions to be developed?
+        *  Recent progress on the gravitational self force problem for compact binaries, now solved numerically to second order in the mass ratio, in the simplest case of the quasi-circular inspiral of nonspinning binaries. Much work remains to be done to obtain accurate waveforms for generic orbits around a spinning black hole (Kerr black hole background spacetime).
-        * Study of resonances in EMRIs (extreme mass ration inspirals), and whether or not they're sustainable or not, in the presence of a third perturbing body. Studies of chaos.
+        *  Study of resonances in EMRIs (extreme mass ration inspirals), and whether or not they're sustainable or not, in the presence of a third perturbing body. Hamiltonian formulation of the binary dynamics, studies of the (non-)integrable nature of the motion and possibility of chaotic motion.
+        * Tidal deformability of black holes in GR and alternative theories of gravity, impact on waveforms for EMRIs, tidally-induced multipole moments and test of the black hole no-hair theorem.
   * All these questions can be repeated in modified gravity theories, see [[gravity|Théories de gravité]], where there are many developments to refine. For the moment scalar-tensor theories (generalized Brans-Dicke) are the only ones with accurate waveforms predicted.
   * Wave forms from other individual sources: important to understand other possible GW signals (continuous waves, bursts, boson stars, other exotic possibilities etc): there could well be new discoveries in the next 10 years, and one needs to be prepared.
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 **Astrophysics, Cosmology with GWs (and other messengers)**
+In the next decade the number of GW events which will be detected will rapidly increase.
+  * O4 2023-2025 -- order 1000-10^4 BBH and BNS
+  * O5 2026-2028 -- 10^5 BBH or more
+  * O6? 2030-2032 -- 10^6 BBH or more.
+With this data, it should be possible to determine, amongst other things, the population of BH in the local universe (mass and redshift distribution), as well as test GR in the strong field regime to high precision.
+Regarding Astrophysics and Cosmology:
   * Using individual sources to measure the Hubble constant and other cosmological parameters (e.g. equation of state of DE), see [[cosmologie|cosmologie]]. Unless there are many GW events with EM counterparts, this goes necessarily hand in hand with astrophysics (Galaxy surveys, cross correlation with LSS, mass distribution of black holes...)
   * probing anisotropic expansion or the cosmological principle with GW data