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Che-Yu Chen (iTHEMS, RIKEN)11/09/2023, 15:30
According to General Relativity, an isolated black hole in vacuum shall be described by the Kerr metric, whose geodesic equations are integrable. The violation of integrability leads to chaos for particles moving around the black hole. This chaotic dynamics could leave imprints on the associated gravitational waveform and could be tested with upcoming observations. In this talk, we discuss the...
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Dr Kyriakos Destounis (Sapienza University of Rome)11/09/2023, 15:50
The historic detection of gravitational waves paved the way for precision gravitational-wave astrophysics to blossom at unprecedented proportions. In this talk, I will focus on extreme-mass-ratio inspirals (EMRIs) that consist of a primary supermassive compact object, and a stellar-mass secondary companion. Even though we are currently performing pertinent tests on order to characterize the...
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Areti Eleni11/09/2023, 16:10
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Viola De Renzis (University of Milano-Bicocca)11/09/2023, 17:00
Black-hole binary spin precession admits equilibrium solutions corresponding to systems with (anti-) aligned spins. Among these, binaries in the up–down configuration, where the spin of the heavier (lighter) black hole is co- (counter-) aligned with the orbital angular momentum, might be unstable to small perturbations of the spin directions. The occurrence of the up–down instability leads to...
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Dr Samuel Upton (Astronomical Institute of the Czech Academy of Sciences)11/09/2023, 17:20
Gravitational self-force theory is the primary way of modelling extreme-mass-ratio inspirals (EMRIs). One difficulty that appears in second-order self-force calculations is the strong divergence at the worldline of the small object, which causes both numerical and analytical issues. Previous work [Phys. Rev. D 95, 104056 (2017); ibid. 103, 124016 (2021)] demonstrated that this could be...
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Viktor Skoupý11/09/2023, 17:40
This work provides gravitational wave energy and angular momentum asymptotic fluxes from a spinning body moving on generic orbits in a Kerr spacetime up to linear in spin approximation. To achieve this, we have developed a new frequency domain Teukolsky equation solver that calculates asymptotic amplitudes from generic orbits of spinning bodies with their spin aligned with the total orbital...
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Angelica Albertini11/09/2023, 18:00
I will present a waveform model for the inspiral of extreme-mass-ratio black hole binaries based on the effective-one-body approach to the two-body problem in general relativity. By means of a gauge-invariant analysis, I will show the agreement of the model with second-order gravitational self-force results for quasi-circular nonspinning binaries. I will then briefly discuss the work in...
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Lukáš Polcar (Charles University)11/09/2023, 18:20
Action-angle (AA) coordinates are commonly used in theoretical description of extreme mass ratio inspirals (EMRI), as they are naturally associated with the two dynamical timescales present in EMRI. However the AA coordinates are rarely used in practical calculations. In our work we implemented analytic methods of canonical perturbation theory to transform geodesic Hamiltonian into AA...
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Panagiotis Giannadakis (King's College London)12/09/2023, 12:00
We investigate the robustness of inflation models to inhomogeneous initial conditions. In the simplest case inflation is described by a single scalar field $\phi$ minimally coupled to gravity with homogeneous initial value $\phi_0 and canonical momentum $\Pi_0 = 0$. However, there is no fundamental reason to reckon that inflation started with such homogeneous initial conditions. In our recent...
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Theodore Anton (Queen Mary University of London)12/09/2023, 12:20
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Giannis Papagiannopoulos12/09/2023, 12:40
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Sergi Sirera Lahoz13/09/2023, 15:30
A nonluminal speed of gravitational waves is a smoking gun signal for the presence of new gravitational physics and hence measurements of this speed can place strong constraints on the theoretical landscape of modified gravity. The ringdown phase of binary black hole mergers, characterised by the so-called quasinormal modes, promises a clean and analytic understanding of deviations from...
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Fatemeh Hossein-Nouri13/09/2023, 15:50
The merger of supermassive black holes (BBH) produces mHz gravitational waves (GW), which are potentially detectable by future Laser Interferometer Space Antenna (LISA). Such binary systems are usually embedded in an accretion disk environment at the center of the active galactic nuclei (AGNs). Recent studies suggest the plasma environment imposes measurable imprints on the GW signal for...
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Georgios Loukes-Gerakopoulos (Astronomical Institute, Czech Academy of Sciences)13/09/2023, 16:10
In this talk we discuss the issue whether the center of the mass of a spinning extended test body moving in a black hole background is just a gauge. The discussion is in the framework of the Mathisson-Papapetrou-Dixon equations, for which a spin supplementary condition is used in order to fix the center of the mass. To get the answer we employ novel and in principle analytical methods of...
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Theodoros Papanikolaou (National Observatory of Athens)13/09/2023, 17:00
Primordial black holes (PBH) can account for a wide variety of cosmic conundra, among which the origin of the primordial magnetic fields threading the intergalactic medium. In this talk, by considering PBHs naturally furnished with a disk due to the vortexlike motion of the primordial plasma around them, we will propose a novel natural ab initio mechanism for the generation a battery induced...
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Dimitra Tseneklidou13/09/2023, 17:20
Core-collapse supernovae are among the most promising future gravitational wave (GW) sources. GW emission is mainly due to the excitation of oscillation modes of the proto-neutron star (PNS) and the stalled accretion shock. Those oscillations will allow in future GW observations to perform asteroseismology to infer properties of the PNS. These oscillations can be represented by a system of...
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Subhajit Dandapat13/09/2023, 17:40
Close hyperbolic encounters of black holes (BHs) generate certain Burst With Memory (BWM) events in the frequency windows of the operational, planned, and proposed gravitational wave (GW) observatories. We provide details of our HyperbolicTD & GW_hyp packages that should allow both LIGO-Virgo-KAGRA (LVK) and Pulsar Timing Array (PTA) consortia to search for such BWM events in their respective...
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Naoki Seto (Kyoto University)13/09/2023, 18:00
We discuss exploration for isotropic gravitational wave backgrounds around 1 mHz by correlation analysis, targeting both parity odd and even polarization modes. Even though the space interferometer LISA alone cannot probe the two modes due to cancellations, the outlook is being changed drastically by the strong development of other space detectors such as Taiji. In fact, a heliocentric...
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IOANNIS TSIOULIS
In parameter estimation calculations of gravitational wave sources, it is useful to know the optimal signal-to-noise ratio of an individual model waveform. We train an artificial neural network on a random sample of one million theoretical waveforms of binary black hole systems with random spins and achieve an accuracy of 97\% in predicting the signal-to-noise ratio. The neural network...
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