Enabling Future Gravitational Wave Astrophysics in the Milli-Hertz Regime

30 June - 25 July 2025

Valeriya Korol, Natalia Korsakova, Lucio Mayer, Martina Toscani, Niels Warburton

Join us to explore the uncharted milli-Hertz regime of the gravitational wave spectrum, a domain soon to be unlocked by space missions. With a special emphasis on the Laser Interferometer Space Antenna (LISA) mission, our workshop also broadens its scope to include other milli-Hertz missions and aims to explore synergies with the next generation of ground-based gravitational wave detectors.


The milli-Hertz regime is unique due to the variety of gravitational wave sources emitting at these frequencies, including binaries of stellar remnants such as white dwarfs, neutron stars, and black holes within our own Galaxy, as well as inspiraling compact objects onto massive black holes (aka Extreme/Intermediate Mass Ratio Inspirals,

E/IMRI)  and mergers between nascent massive black holes (MBH) at cosmic dawn. This regime is also unique in terms of waveform modelling, data analysis and data interpretation, presenting challenges that call for a community-driven approach.


Our workshop will bring together leading experts and early career scientists in the field of theoretical modelling (from astrophysics to numerical relativity), electromagnetic observations, and gravitational wave data analysis, aiming to prepare the community for the new kind of gravitational wave data and to enable groundbreaking astrophysics in the milli-Hertz regime. The format will balance scientific talks, interactive tutorials, and open discussions, creating an ideal environment for initiating new collaborations and consolidating ongoing projects. More broadly, we strive to foster a community where interdisciplinary and creative collaborations can flourish.

Week 1 (30th June - 4th July): Astrophysical Modelling and Uncertainties

• Review and assess state-of-the-art astrophysical models.

• Identify gaps and uncertainties in mHz GW source modelling.

Key topics to be discussed include:

– Robustness of stellar binary modelling against assumptions on stability of mass transfer, accretion onto compact objects, common envelopes, and tides.

– Predicting MBH binaries/EMRI/IMRI event rates and their key waveform properties.

– Existence and distribution of intermediate-mass black holes.

– Synergies with upcoming electromagnetic surveys.


Week 2 (7th - 11th July): Waveform Modelling Challenges

• Outline a road-map for addressing challenges in waveform modelling before 2030s.

• Access the required waveform accuracy for the mHz data analysis.

Key questions to be discussed include:

– Integrating post-Newtonian and numerical relativity simulations to provide predictions for waveforms under realistic orbital configuration of the mHz GW sources.

– Explore the possibility of extending black hole perturbation theory for IMRIs.

– Including environmental effects in GW waveforms.

– Advances and applicability of emerging methods based on effective field theory and amplitude scattering techniques.


Week 3 (14th - 18th July): Data Analysis and Parameter Estimation

• Discuss data analysis complexities; in particular challenges of the “global fit” approach.

• Focus on precise source parameter estimation and accurate source subtraction to facilitate the analysis of stochastic backgrounds.

Key questions to be discussed include:

– Utilising electromagnetic observations of Galactic binaries for instrument noise estimation.

– Identify waveforms that effectively capture the diversity and complexity of astrophysical populations for each source type while optimising computational efficiency.

– Formulate astrophysically motivated priors for the global fit analysis.

– Discuss strategies for extracting astrophysical sources from GW data to analyse stochastic signals.


Week 4 (21st - 25th July): Data Interpretation via Astrophysical Models

• Build upon insights from previous weeks’ discussions to explore the scientific interpretation of mHz GW data using astrophysical models.

• Develop astrophysics-focused mock data challenges to prepare the community for future data interpretation.

Key questions to be discussed include:

– Re-discovering our Galaxy using mHz GW detections.

– Understanding MBH formation through GW detections.

– Leveraging GW event rates to study physical processes in galactic nuclei.

– Identifying promising electromagnetic counterparts for mHz GW sources