GRAPPA Colloquia 2024-25




Date Speaker Host @ GRAPPA Title Abstract Affiliation Location
10/02/2025 Julien Billard Maxime Pierre Searching for Light Dark Matter with the future TESSERACT experiment at LSM The future TESSERACT (Transition Edge Sensor with Sub-Ev Resolution and Cryogenic Targets) experiment aims at searching for light Dark Matter candidates in the sub-GeV range down to the keV-scale from the Laboratoire Souterrain de Modane. To do so, it is being designed to be highly sensitive to both nuclear recoil DM (NRDM) and electron recoil DM (ERDM) interactions. Multiple target materials will be used, sharing identical readout using Transition Edge Sensors operated at 10 mK. In addition to maximizing sensitivity to a variety of DM interactions, this provides an independent handle on instrumental backgrounds. Three detector technologies will be implemented: HeRALD which will use superfluid helium-4 as a target material, SPICE which will use polar and scintillating crystals, and Ge/Si semiconductors that will be developed by the French TESSERACT collaborators. In this talk, I will give an overview of the design status of the future TESSERACT experiment, discuss its different detector technologies with an emphasis on the Ge/Si one currently being developed in the context of the Ricochet neutrino experiment, and will present the science prospect of the experiment. Institut de Physique des 2 Infinis de Lyon (IP2I), Lyon, France C4.174, GRAPPA, Science Park 904, Amsterdam
24/02/2025 Luciano Rezzolla Gianfranco Bertone Binary Neutron Stars: from macroscopic collisions to microphysics I will argue that if black holes represent one the most fascinating implications of Einstein's theory of gravity, neutron stars in binary system are its richest laboratory, where gravity blends with astrophysics and particle physics. I will discuss the rapid recent progress made in modelling these systems and show how the gravitational signal can provide tight constraints on the equation of state and sound speed for matter at nuclear densities, as well as on one of the most important consequences of general relativity for compact stars: the existence of a maximum mass. Finally, I will discuss how the merger may lead to a phase transition from hadronic to quark matter. Such a process would lead to a signature in the post-merger gravitational-wave signal and open an observational window on the production of quark matter in the present Universe. Goethe University, Frankfurt, Germany C4.174, GRAPPA, Science Park 904, Amsterdam
10/03/2025 Jonathan Gair Maxime Pierre Opportunities and challenges in SBI for future gravitational wave detectors Simulation based inference (SBI) is becoming increasingly important in the analysis of data from the current generation of ground-based gravitational wave detectors. Plans are well advanced for future generations of detector, on the ground, and also in space. These future detectors will pose many more challenges that will test the boundaries of what is possible with both classical and machine-learning based methods. In this talk, I will provide an overview of the current state of the art in SBI for gravitational wave inference, focussing in particular on the DINGO analysis package. I will then describe the many new challenges that future detectors will pose, focussing on the case of LISA, the planned space-based gravitational wave detector due for launch in the mid 2030s. I will describe the classical approaches that are being developed to tackle the LISA data analysis problem and highlight areas where SBI methods could play a critical role in addressing the outstanding problems. Max Planck Institute for Gravitational Physics (Albert Einstein Institute), Potsdam, Germany C4.174, GRAPPA, Science Park 904, Amsterdam
31/03/2025 Max Welling Gianfranco Bertone Can AI Change the Paradigm for Scientific Discovery? While Large Language Models and the race towards AGI have captured all the attention (and drama). However, AI is also disrupting the way we do science. By shifting as much work as possible from experiments to the digital domain we can dramatically accelerate our understanding and prediction of nature, and design of new molecules and materials with desired properties. Key recent successes include weather prediction, protein design and folding (for which the 2024 Nobel prize was awarded) and Machine Learned Force Fields for chemical simulations. These developments are fundamental to keep Moore's Law alive (better semiconductors), develop new drugs, develop new sustainable energy solutions (nuclear fusion, synthetic fuels, batteries) and remove the excess carbon dioxide from our atmosphere (Carbon Capture and Removal). In this talk I will give an overview of some of these developments and argue that Europe needs to invest in this area to stay competitive and leave a clean planet for our children. University of Amsterdam, The Netherlands C4.174, GRAPPA, Science Park 904, Amsterdam
07/04/2025 Lucio Mayer Rodrigo Vicente The cosmic evolution of massive black hole binaries and their nuclear environment; the fil rouge connecting galaxy formation, accretion disk physics and gravitational wave astronomy Massive black hole binaries emerge in galactic nuclei as a consequence of the dynamics of hierarchical structure formation. Understanding the pairing and binary sinking process until they enter the in-spiral phase governed by gravitational wave emission is thus tightly connected with understanding the physics of galaxy formation and evolution. It is a computationally daunting task involving a huge range of spatial and temporal scales. The rate of GW in-spiral events that LISA will detect as well as their properties cannot be predicted without modelling the preceding phases. I will present an overview of the challenges that numerical simulations and semi-analytical models are facing, hinting at a potential "last kiloparsec problem". I will make the case for a new, different approach based on using machine learning to build multi-scale emulators replacing direct numerical simulations. I will then move on to describe how the modelling of the GW in-spiral signal for sources in the LISA band requires accounting for the environmental perturbations induced by surrounding matter. In particular, I will show results from some of the first post-newtonian hydrodynamical simulations that quantify the phase-shift induced on in-spiral waveforms from the residual gas torques from the circumbinary disk in which the two black holes are evolving. Environmental perturbations leave the imprint of accretion disk physics on the waveforms, at a minimum in the form of a phase-shift, and most likely also through additional complex higher frequency modulations, "dirty waveforms", which are caused by local fluctuations in the accretion flow dynamics the black holes. These effects must be understood as they can be degenerate with deviation from General Relativity, and are also a unique probe of physics near black holes for scales well below those accessible via electromagnetic waves. Department of Astrophysics, University of Zurich, Switzerland C4.174, GRAPPA, Science Park 904, Amsterdam
14/04/2025 Jia Liu Youyou Li Our Universe in Simulation Ongoing and upcoming cosmological surveys—including the Simons Observatory, LiteBIRD, CMB-S4, Rubin LSST, Euclid, DESI, PSF, SPHEREx, and the Roman Space Telescope—will deliver observations of unprecedented precision. Joint analyses across these surveys will be essential for uncovering fundamental physics, including the nature of inflation, dark energy, dark matter, neutrino mass, and more. In this talk, I will discuss the opportunities, challenges, and strategies for simulating our universe across multiple wavelengths to realize these goals. Kavli IPMU, University of Tokyo, Japan C4.174, GRAPPA, Science Park 904, Amsterdam
12/05/2025 Malcolm Fairbairn Youyou Li TBA TBA King's College, London, UK C4.174, GRAPPA, Science Park 904, Amsterdam
02/06/2025 Carlos Frenk Rodrigo Vicente TBA TBA Institute for Computational Cosmology, Durham University, UK C4.174, GRAPPA, Science Park 904, Amsterdam