Gravitational Wave Probes of Black Hole Environments

May 26, 2025, 9:00 AM → May 30, 2025, 6:00 PM Europe/Rome

205 (IFPU)

Andrea Maselli (GSSI), Enrico Barausse (SISSA), Gianfranco Bertone (University of Amsterdam, GRAPPA)

 

Gravitational wave (GW) observations from binary black hole (BBH) mergers have provided new insights into strong-field gravity. A growing area of research focuses on environmental effects, where dark matter or other surrounding matter can influence the BBH dynamics and leave detectable imprints on GW signals. Dark matter, in particular, could form dense regions around black holes, potentially seeded by primordial black holes or amplified through processes like adiabatic growth or superradiance, modifying the resulting GW emission. 

This workshop will examine the impact of such environments on BBH waveforms, with a focus on detecting and constraining these effects using GW observations. We will explore novel data analysis techniques, including machine learning and simulation-based inference (SBI), to enhance parameter inference and disentangle environmental signatures. The workshop aims to foster interdisciplinary collaboration in this emerging field by bringing together experts from gravitational wave astronomy, dark matter theory, and machine learning.

 

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Organizers

Enrico Barausse (local contact, SISSA) 

Gianfranco Bertone  (University of Amsterdam, GRAPPA)

Andrea Maselli (GSSI)

 

 

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Adriatico Guesthouse

Adriatico Guesthouse cafeteria

BUS 6 (city) How to get to IFPU .pdf

Getting to IFPU.pdf

ICTP cafeteria / canteen

IFPU website

Trieste tourism website

Walking directions from the Adriatico Guesthouse to IFPU.pdf

Monday, May 26

9:00 AM → 9:30 AM Coffee and Welcome

9:30 AM → 10:00 AM Talk- "NR: What is it good for?”: Katy Clough

I will discuss the ways in which numerical relativity (NR) is useful for studying dark matter environments around black holes in the strong gravity regime, and highlight its inherent limitations. I will mainly focus on open questions and plans for future work.

KCloughMay2025.pdf

10:00 AM → 10:30 AM Talk- Probing ultralight dark matter with gravitational waves: Rodrigo Vincente

The strong gravitational fields around black holes may be the best (and only) way to probe the nature of dark matter, if it is ultralight. Gravitational waves provide us with the cleanest channels into those regions.

In my talk, I will discuss what current LVK observations can tell us about the presence of ultralight bosons around black hole binaries. I'll also argue that future gravitational-wave observations have the potential to detect and measure the mass of an ultralight dark matter particle to high precision.

10:30 AM → 11:00 AM Break

11:00 AM → 11:30 AM Talk- Luminous dark photon clouds: Cristina Mondino

Black hole superradiance of dark photons that kinetically mix with the photon are spontaneously filled with an electron positron plasma which rotates around the black hole. The system results in a very luminous cloud, emitting across the whole electromagnetic spectrum. I will present results of a recent multimessenger search for continuous wave signals from pulsating sources and its interpretation in terms of dark photon signals from a population of galactic black holes.

IFPU_May2025.pdf

11:30 AM → 12:00 PM Discussion (Barausse)

12:00 PM → 2:30 PM Lunch

2:30 PM → 4:30 PM Small group discussions

Tuesday, May 27

9:00 AM → 9:30 AM Coffee

9:30 AM → 10:00 AM Talk- The mass in the Galactic Center: Stefan Gillessen

Near-infrared observations of individual stellar orbits have revealed that the Galactic Center hosts a compact mass of around 4.3 million solar masses, honored with the Nobel prize in physics in 2020. By the advent of near-infread interferometry, the resolution and astrometric precision have been increased recently by almost an order of magnitude, turning the stellar system around Sgr A into a laboratory for testing general relativity aorund a large mass. Further, stellar orbits probe the Newtonian mass content in the Galactic Center, and provide stringent constraints on how much dark objects can reside around Sgr A, and constitutes thus a test case for the dynamical modelling used to predict extreme-mass ratio inspiral rates for gravitational wave observations.

10:00 AM → 10:30 AM Talk- Environmental Effects on BH-BH GW Waveforms: Cole Miller

As we move into the next generation of gravitational-wave detectors in space (LISA) and on the ground (ET), it becomes relevant to consider environmental effects on the gravitational waveforms from binary black hole coalescences. These include the possible effects of gas as well as the gravitational perturbations from a third object outside the binary. I will review and give formulae for several such effects. Primarily, I will invite discussion of whether altered waveforms will be distinguishable from the waveforms produced by standard isolated binaries with modified parameters.

miller (2).pptx

10:30 AM → 11:00 AM Break

11:00 AM → 11:30 AM Talk- Extreme mass ratio inspirals in accretion disks: Laura Sberna

Gravitational-wave observations of extreme mass ratio inspirals can directly probe the environments of galactic nuclei, thanks to the torques that accretion disks can exert on the secondary. I will discuss recent progress on understanding the detectability of realistic disk torques with LISA, including stochastic torque oscillations and orbital eccentricity. I will also present preliminary results on relativistic corrections to the disk torque.

11:30 AM → 12:00 PM Discussion (Bertone)

12:00 PM → 2:30 PM Lunch

2:30 PM → 4:30 PM Small group discussions

Wednesday, May 28

9:00 AM → 9:30 AM Coffee

9:30 AM → 10:00 AM Talk- Environmental effects of dark matter spikes on EMRIs: Theophanes Karydas

Dark matter halos may naturally lead to the formation of dark matter overdensities around black holes known as “spikes”. These environments can perturb the dynamical evolution of a companion object orbiting inside of them, and thus significantly alter the emitted gravitational waveform (GW). For extreme mass ratio inspirals (EMRIs), the accurate modelling of waveforms is key to successfully extracting information about their environments.

In this talk, I will introduce the topic, discuss what we’ve learned about modelling these systems and present some implications arising from the strong gravity of the two black holes.

karydas_ifpu.pdf

10:00 AM → 10:30 AM Talk: Mudit Garg - "Characterising sub-parsec environment of LISA Massive Black Hole Binaries"

Title: Characterising sub-parsec environment of LISA Massive Black Hole Binaries

Abstract: Our current understanding is that an environment – mainly consisting of gas or stars – is required to bring massive black hole binaries (MBHBs) with total mass ∼ [10^4, 10^7] MSun from parsec scale to near-merger. During their final years of inspiral, MBHBs will radiate gravitational waves (GWs) at near-milliHz frequencies that will be observed by the recently adopted space-based mission LISA. I will demonstrate, using a realistic Bayesian data analysis approach, the importance of modeling gas-induced perturbations and eccentricity in the gravitational waveform of LISA MBHBs to constrain properties of the environment, reduce biases on inferred binary parameters, and mitigate systematics in tests of general relativity. Moreover, I will show results from my hydrodynamical simulations studying a MBHB in the final years of its merger. LISA will launch in a decade, making this exploration exciting and valuable in unlocking the mysteries of MBHB evolution.

10:30 AM → 11:00 AM Break

11:00 AM → 11:30 AM Discussion (Maselli)

11:30 AM → 2:00 PM Lunch

2:00 PM → 4:00 PM Small group discussions

8:00 PM → 10:00 PM SOCIAL DINNER

Dinner at the Antica Trattoria Suban
Address: Via Emilio Comici, 2, 34128 Trieste TS
Phone: 040 54368

Thursday, May 29

9:00 AM → 9:30 AM Coffee

9:30 AM → 10:00 AM Talk- Matters of Relativity: Andrea Maselli

Coalescing compact binaries serve as natural laboratories where black holes act both
as targets for gravitational wave observations and as moving probes of their surrounding
medium. In this talk, I will explore how asymmetric binaries—a promising new class of
sources to be observed by next-generation detectors—can be used to investigate the
properties of non-vacuum spacetimes in which they evolve.

I will emphasize the importance of employing fully relativistic approaches to accurately describe these systems and highlight some intriguing effects that emerge from such treatments. Finally, I will show that in certain scenarios, the influence of environmental effects can be captured with minimal modifications to standard self-force methods, offering a simplified yet accurate description of their evolution.

10:00 AM → 10:30 AM Talk- Sequential simulation-based inference for extreme mass ratio inspirals: Philippa Cole

Extreme mass ratio inspirals are a key target for next-generation space-based gravitational wave detectors because they have a rich phenomenology that could offer new astrophysics and fundamental physics insights. However, their dynamics are complicated to model, and they will be buried amongst a large population of other sources in the milliHertz frequency band, with a background of non-stationary and non-Gaussian noise. Searching for these systems and measuring their parameters therefore presents a difficult challenge.

Simulation-based inference methods could offer solutions to some of these challenges. I will show parameter estimation results for extreme mass ratio inspiral systems achieved using sequential simulation-based inference, specifically truncated marginal neural ratio estimation. I will highlight the benefits of this approach with respect to traditional likelihood-based methods, and discuss the broader context in which such a pipeline will need to be embedded as well as how and when environmental effects should be considered.

SBI_EMRIs_Trieste_FocusWeek.pdf

10:30 AM → 11:00 AM Break

11:00 AM → 11:30 AM Talk- A common framework for consistently modelling perturbed EMRIs: Maarten van de Meent

Extreme Mass-Ratio Inspirals are a promising source for precision gravitational wave astronomy. This promise can only be fulfilled if we manage to produce equally precise waveform models. Producing such models is extremely challenging, even in “vanilla” vacuum general relativity, requiring intricate gravitational self-force (GSF) calculations. This can make modelling beyond vacuum GR perturbations to EMRIs seem daunting. Luckily, at leading post-adiabatic order the calculation of GSF and beyond vacuum GR corrections completely decouples, allowing both problems to be pursued independently and in parallel. We review the common post-adiabatic framework for including perturbations to EMRIs, and classify different potential contributions.

11:30 AM → 12:00 PM Discussion (Barausse)

12:00 PM → 2:30 PM Lunch

2:30 PM → 4:30 PM Small group discussions

Friday, May 30

9:00 AM → 9:30 AM Coffee

9:30 AM → 11:00 AM Wrap up: Barausse / Bertone

11:00 AM → 11:30 AM IFPU Colloquium (Bertone)

11:30 AM → 1:30 PM Lunch

1:30 PM → 3:30 PM Small group discussions