Gravitational Waves, relativistic celestial mechanics and black hole physics

• Grant number: 24/23389-5
• Support Opportunities: Research Grants - Visiting Researcher Grant - International
• Start date: May 01, 2025
• End date: April 30, 2026
• Field of knowledge: Physical Sciences and Mathematics - Physics - General Physics
• Principal Investigator: Riccardo Sturani
• Grantee: Riccardo Sturani
• Visiting researcher: Alexandre Le Tiec
• Visiting researcher institution: Observatoire De Paris, Meudon/Obspm, France
• Host Institution: Instituto de Física Teórica (IFT). Universidade Estadual Paulista (UNESP). Campus de São Paulo. São Paulo , SP, Brazil
• Associated research grant: 22/06350-2 - Fundamental physics and LIGO, AP.ESP

Abstract

Binary systems composed of neutron stars and black holes lighter than 100solar masses are among the most promising sources of gravitational waves (GWs)forexisting (Advanced LIGO, Advanced Virgo, KAGRA), planned (INDIGO) and proposed(Cosmic Explorer, Einstein Telescope) ground-based interferometric detectors.Moreover, during the coming decade the space-based LISA mission is expectedto observe GWs resulting from the merger of pairs of supermassive black holesfrom tens of thousands to tens of millions solar masses.For both present and planned observatories a crucial ingredient to maximizedthe physics output of detections is the availability of precise and accuratewaveform models, whose development is currently under vibrant investigationwith several perturbative (post-Newtonian, post-Minkowskian, self-force)and non-perturbative methods (numerical relativity).However, using waveform templates with current accuracy in future GW data, would lead to systematic uncertainties comparable or largerto statistical ones.Here we propose to pave the way to a new approach to solving the general relativistic 2-body problem, leading to theconstruction of template waveforms that will be both Physically motivated and with reduced modelling errors.This will be achieved via black hole perturbation theory to hybridize post-Newtonian and post-Minkowskian-based ones. A milestone in this direction has beenachieved with the construction of waveforms for a non-spinning compact object orbiting a Schwarzchild black hole of much larger mass, in the simplest case of an adiabatic quasi-circular inspiral,including the relative first-order corrections in the small mass ratio in the phasing and amplitude.The next natural step to be undertaken in this project would be to include in the perturbative waveforms the transition to plunge, by relaxing the assumption of adiabaticity.The long-term objective is of course to produce waveforms in the general case of a (spinning) compact object moving on a generic (bound) orbit around a rapidly rotating (Kerr) black hole.This is also the distant objective for GW source modelling of extreme mass mass ratio (inspiral) systems, or EMRI, likely sources for LISA.Therefore, the completion of the main objective of this research project relies heavily on the successful development of templates for EMRIs, to which the visiting professor contributed actively. (AU)