Diego Blas, Institut de Física d'Altes Energies (IFAE)

Title: Closing gaps in the GW spectrum: Ideas to detect microHz and high frequency GWs

Abstract: In this talk I will describe some recent ideas to find GWs in two bands which are not covered by traditional methods, and that have a rich potential for astrophysics and fundamental physics.

Slides can be found here

Stephen Green, University of Nottingham 

Title: Simulation-Based Inference for Gravitational Waves

Abstract:
During the first half of the fourth LIGO-Virgo-KAGRA observing run, we observed gravitational waves from merging binaries roughly every three days. While this routine detection promises exciting results, it is becoming a significant challenge to analyze all events using our most sophisticated theoretical models. In this talk, I will describe how to overcome these challenges using deep learning techniques for rapid, amortized Bayesian inference. This approach uses simulated data to train neural networks (such as normalizing flows) to represent the Bayesian posterior. Once trained, sampling becomes extremely fast. I will also describe how to establish full confidence in results using importance sampling, as well as initial results on population inference and future prospects to treat realistic noise.

Slides can be found here

Syksy Räsänen, University of Helsinki

Title: Walking on a bed of nails - effect of dark matter discreteness on light propagation

Abstract: In general relativity, light travels on null geodesics when the curvature of the wavefront and the spacetime are much smaller than photon energy. Localised dark matter particles can source large spacetime curvature, pushing light off null geodesics. I discuss how to take this effect into account, and how it may affect cosmological redshift and distance. 

Slides can be found here

Fabian Bautista, Institut de Physique Théorique (IPhT), Saclay 

Title: From two-dimensional CFTs to Kerr Binary Systems

Abstract: In this talk we will discuss a new window into the solution of Heun differential equations arising in black hole perturbation theory using the tools of two-dimensional CFT. Kerr Compton amplitudes for massless perturbation of generic spin-weight s, are written in compact form in terms of the so-called Nekrasov-Shatashvili functions; their symmetry properties are also discussed. These are then used as building blocks to study the scattering of two Kerr black holes with generic spin orientation. Comparison to conservative observables for bounded systems computed via first-order gravitational self-force methods are shown.

Title: Probing the host environments of compact binaries

Abstract: When, where, and how compact binaries form is still a mystery, and observations from the LIGO-Virgo-KAGRA detectors are starting to shed light on this. In this talk, I will discuss ways of probing host environments of these binaries. First, I will show how the redshift evolution of the binary black hole merger rate can be used to constrain the parameter space of the host galaxies of such mergers. Then, I will discuss how a nonzero centre of mass acceleration affects the observed signal in our detectors, and how one can differentiate between candidate host environments by measurements of acceleration. I will end with some prospects along these lines for the future.