What: phenomgrav astrophysics seminar

When: July 7th, 2025, 15:00-16:00 CEST

Where: Building C - Room 131, ground floor

Speaker: Dr. Stefano Rinaldi - Institut für Theoretische Astrophysik, Universität Heidelberg

Title: Expect the unexpected – Inference of the black hole distribution using both parametric and non-parametric methods

Abstract: Black holes are the remnants of the most massive of stars, and characterising their population using gravitational wave (GW) observations can help us understand the astrophysical processes governing the life and death of stars. In this picture, non-parametric methods represent an excellent agnostic tool to describe our observations and guide the development of new astrophysical models; on the downside, they lack the interpretability carried by physically informed models. During this talk, I will present two approaches designed to combine the strengths of parametric and non-parametric methods: 1) the concept of augmented mixture model – a weighted superposition of astrophysical and non-parametric models capable of accounting for unforeseen features in the black hole spectrum - and 2) a procedure that first performs a non-parametric (data-driven) reconstruction of the underlying distribution, and then remaps these results onto a posterior for the parameters of an informed model.

What: phenomgrav astrophysics seminar

When: June 10th, 2025, 15:00-16:00 CEST

Where: Building C - Room 248, first floor

Speaker: Dr. Alice Garoffolo - UPenn University

Title: Gravitational waves in wave optics

Abstract: An intriguing aspect of gravitational wave lensing is the emergence wave-effects: interference and diffraction patterns in the waveforms due to finite size effects, occurring when the wave’s wavelength is comparable to the Schwarzschild radius of the lens. These phenomena are particularly interesting because they induce frequency dependent modifications in the waveforms, allowing for a better lens’ parameter estimation, especially if the lensing event has an electromagnetic counterpart in the opposite optical regime.Despite the promising potential of wave-optics effects, our current theoretical tools, based on the diffraction integral, rely on two main assumptions that limit their effectiveness: the eikonal and paraxial approximations on one hand, and the neglect of spin effects on the other. In this talk I will present our new formalism, based on the established proper time technique in field theory, illustrating its robustness as the generalization of the diffraction integral, going beyond all of the limitations mentioned.

What: phenomgrav astrophysics seminar

When: June 5th, 2025, 10:00-11:00 CET

Where: Building C - Room 248, first floor

Speaker: Farid Thaalba - University of Nottingham

Title: Predictivity in Extensions of General Relativity and the Standard Model

Abstract: Extensions of General Relativity often suffer from an ill-posed initial value problem, severely limiting their predictive power. In this work, we tackle this challenge through a numerical investigation of scalar-Gauss-Bonnet gravity. We demonstrate that, within the effective field theory paradigm, the careful inclusion of specific interactions is crucial for overcoming this issue, offering new insights that could significantly enhance the predictivity of extensions of General Relativity.

For previous seminar, see here.