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Laura Bernard (LUTH - CNRS / Observatoire de Paris)08/10/2024 09:25
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Philippe Grandclément (LUTH)08/10/2024 09:30
Numerical relativity enables to simulate the full coalescence of binary compact objects. Using appropriate initial data for such evolutions is crucial. This is not an easy task: not only should those data describe as accurately as possible the physical situation one wishes to simulate, but they also must verify a subset of Einstein's equations known as the constraint equations. I will adopt...
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Dr Sashwat Tanay (LUTH, Paris Observatory)08/10/2024 10:00
Accurate modeling of binary black hole (BBH) dynamics is crucial for the detection of gravitational waves emitted by them. We focus on the so-called "orbit-averaged" spinning BBH system at the second post-Newtonian (PN) order. We discover that it is a Hamiltonian system and we present its Hamiltonian. We then establish that it is an integrable system (one that possesses action-angle variables...
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Christopher Aykroyd (SYRTE, Observatoire de Paris)08/10/2024 10:20
Since their onset, post-Newtonian schemes have been consistently effective in describing binary orbits, achieving progressively higher order expansions. Their aim is to essentially produce 'matter-only' equations of motion by elimination of the metric degrees of freedom. In the ADM framework, this corresponds to the computation of a matter-only Hamiltonian.
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Yet despite these advancements,... -
Stavros Mougiakakos (LUTH, Observatoire de Paris, Meudon)08/10/2024 11:00
In this talk, we will review applications of EFT approaches in perturbative analytical approaches in GR. Specifically, we will discuss the Post-Newtonian (PN) and the Post-Minkowskian (PM) worldline Effective Field Theory (EFT) formalisms. Finally, we will discuss possible avenues towards the application of these methods in the Self-Force expansion based on recent work.
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Sofia Bisero (GEPI, Observatoire de Paris, Université PSL, CNRS)08/10/2024 11:20
The Einstein Telescope (ET), next generation gravitational wave (GW) interferometer, will explore a large volume of the Universe detecting up to ∼ 10$^{5}$ binary neutron star system mergers (BNS) beyond z ∼ 3, clearly revolutionizing GW multi-messenger (MM) astrophysics. Given the huge amount of EM counterpart candidates that will be provided by optical-NIR photometric observations within the...
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Karim Abd El Dayem (Observatoire de Paris (LESIA))08/10/2024 11:40
In this presentation, we investigate the detection of the spin and quadrupole moment of the black hole at the center of the galaxy called Sgr A. These parameters affect the astrometric and spectroscopic observations of stars in the close vicinity of the black hole (S stars). Here, we consider putative stars that are closer to Sgr A, and thus much more affected by the spin effects. Such...
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Arianna Foschi (Observatoire de Meudon)08/10/2024 12:00
The motion of S2, one of the stars closest to the Galactic Center (GC), has been measured accurately and used to study the compact object at the centre of the Milky Way. It is commonly accepted that this object is a supermassive black hole but the nature of its environment is open to discussion. In this talk I’m going to show how the motion of S2 can be used to investigate the possibility that...
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Katy Clough08/10/2024 14:00
Engrenage is a spherically symmetric BSSN code designed for teaching Numerical Relativity (NR), which is the solution of the Einstein Equations of General Relativity (GR) using numerical methods. The code includes a scalar field (obeying the Klein Gordon equation for a minimally coupled spin 0 field) as the matter source of the metric curvature. It currently includes two physical examples - a...
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Katy Clough08/10/2024 15:50
Engrenage is a spherically symmetric BSSN code designed for teaching Numerical Relativity (NR), which is the solution of the Einstein Equations of General Relativity (GR) using numerical methods. The code includes a scalar field (obeying the Klein Gordon equation for a minimally coupled spin 0 field) as the matter source of the metric curvature. It currently includes two physical examples - a...
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Dr Quentin Baghi (APC | Université Paris Cité)10/10/2024 09:30
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Eve Dones (LUTH - Observatoire de Paris)10/10/2024 09:50
The study of tidal effects between compact objects such as neutron stars is particularly promising to better understand their physics. Including these effects in our waveform models could allow us to probe their internal structure, but also possibly to distinguish signals coming from black holes, neutron stars or even more exotic objects. This will be of paramount importance when interpreting...
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Hao-Jui Kuan10/10/2024 10:10
Gravitational waves provide a pure probe for fundamental physics that manifests in coalescing binaries, supplementing the electromagnetic counterparts to form multimessenger signals. Precise measurement of waveforms can help us learn about the yet-fully-explored tidal response of neutron stars in late inspiral stages and about effects beyond general relativity (GR). In particular, the waveform...
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Alan Tsz Lok Lam (Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Potsdam)10/10/2024 10:30
We study binary neutron stars in the framework of Damour-Esposito-Farese-type scalar-tensor theory of gravity with a massive scalar field using numerical relativity simulations, focusing on the properties of post-merger remnant. We found that the threshold mass for prompt collapse is raised in the presence of the excited scalar field. Our simulation results also suggest the existence of...
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Masaru Shibata10/10/2024 11:15
By performing longterm magneto/viscous radiation hydrodynamics simulations in general relativity for the collapse of rapidly rotating massive stars, we explore the collapsar scenarios. I will first show that stellar explosion with the explosion energy of 10^51—10^52 erg can be induced even after the formation of a black hole if a massive torus surrounding the black hole, which becomes the...
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Maxence Corman10/10/2024 14:00
In recent years, gravitational wave observations of compact objects have provided new opportunities to test our understanding of gravity in the strong-field,highly dynamical regime. To perform model-dependent tests of General Relativity with these observations, one needs accurate inspiral-merger-ringdown waveforms in alternative theories of gravity.
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In this talk, we consider two generally... -
10/10/2024 15:15
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