YOUNGST@RS - Lost in Translation: The languages of Gravitational Waves

19 Jan 2026, 00:00 → 21 Jan 2026, 23:40 Europe/Berlin

Mainz Institute for Theoretical Physics, Johannes Gutenberg University

In recent years, the modelling of gravitational wave sources has become a cornerstone of theoretical and numerical relativity. Multiple communities—working with distinct formalisms such as Self-Force, Effective One Body (EOB), Effective Field Theory (EFT) and post-Newtonian approximations—have developed powerful tools to describe the two-body problem with increasing precision. Each of these approaches is advanced enough to come with its own set of language, notation, conceptual framework, and computational tools.

The workshop aims to bridge this gap and bring these communities closer together. This will be done by providing a mix of beginner friendly lectures, hands on coding sessions, plenary overviews together with state of the art research talks for each of the fields.

Monday 19 January

09:50 → 10:00 Welcome

10:00 → 10:50 Julio Parra-Martinez: PM/SF Synergies

tba

10:50 → 11:00 Break

11:00 → 11:30 Gustav Uhre Jakobsen: Theoretical setup for scattering in PM

Abstract: The weak-field regime of black hole scattering is naturally described in the post-
Minkowskian (PM) approximation. Here, the gravitational metric is expanded
around flat Minkowski space-time and the black holes appear as point-like
particles in an effective field theory. High-precision computations of observables of
this system can — via a mapping to bound dynamics — be used to inform
gravitational waveform models relevant to current gravitational wave detectors. In
this lecture, I will give an accessible introduction to the main physical assumptions
and methods of PM computations. As a concrete example, I will consider the
calculation of the total energy lost by the black holes to gravitational waves at the
leading 3PM order. Several aspects of this example illustrate the challenges at
higher perturbative orders and for other physical observables.

Presentation_Gustav_Jakobsen.pdf

11:30 → 11:45 Break

11:45 → 12:15 Gustav Uhre Jakobsen: Theoretical setup for scattering in PM

Abstract: The weak-field regime of black hole scattering is naturally described in the post-
Minkowskian (PM) approximation. Here, the gravitational metric is expanded
around flat Minkowski space-time and the black holes appear as point-like
particles in an effective field theory. High-precision computations of observables of
this system can — via a mapping to bound dynamics — be used to inform
gravitational waveform models relevant to current gravitational wave detectors. In
this lecture, I will give an accessible introduction to the main physical assumptions
and methods of PM computations. As a concrete example, I will consider the
calculation of the total energy lost by the black holes to gravitational waves at the
leading 3PM order. Several aspects of this example illustrate the challenges at
higher perturbative orders and for other physical observables.

12:15 → 12:40 Q&A Session

12:40 → 14:00 Lunch Break

14:00 → 14:30 Gregor Kalin: How not to compute gravitational observables at 6PM

Abstract: State-of-the-art computations for gravitational observables (in the scattering
regime) rely on a plethora of algorithms, tools and software. In this talk I will give an
overview over the whole machinery with a focus on the strengths, weaknesses and
-- most importantly -- future potential of the different approaches. The topics will
include discussions of abstract algorithms and ideas, as well as explicit
implementations at a low level.

Presentation_Gregor_Kaelin.nb

14:30 → 14:45 Break

14:45 → 15:15 Gregor Kalin: How not to compute gravitational observables at 6PM

Abstract: State-of-the-art computations for gravitational observables (in the scattering
regime) rely on a plethora of algorithms, tools and software. In this talk I will give an
overview over the whole machinery with a focus on the strengths, weaknesses and
-- most importantly -- future potential of the different approaches. The topics will
include discussions of abstract algorithms and ideas, as well as explicit
implementations at a low level.

15:15 → 15:30 Break

15:30 → 16:00 Mathias Driesse: Conservative Black Hole Scattering at Fifth Post-Minkowskian and Second Self- Force Order

Abstract: Motivated by the need for high-precision binary dynamics, I will present
preliminary results for the conservative scattering angle and impulse at fifth post-
Minkowskian and second self-force order, obtained using the WQFT framework. I
will also show how results resolve ambiguities related to a mysterious pole in the
physical region. Finally, I will present some recent comparisons between selfforce,
NR and our PM data (at 1SF) to demonstrate the physical accuracy of our
results and to motivate comparisons at the next SF order.

Presentation_Mathias_Driesse.pdf

16:00 → 16:10 Break

16:10 → 16:40 Lara Bohnenblust: Scattering Waveforms from QFT & WQFT

Abstract: In this talk, I present the calculation of the scattering waveform up to next-toleading
order in the post-Minkowskian (PM) expansion. I compare two
complementary strategies: the traditional QFT approach and the WQFT framework.
I discuss in detail the construction of the relevant five-point amplitude using the
numerical unitarity method and illustrate the practical use of the amplitudes code
“Caravel”. I then outline the WQFT procedure, which allows us to lift seven-point
tree amplitudes to the one-loop integrand. These two approaches provide
independent cross-checks, and I explain how this validation works in practice. I
conclude by discussing the resulting scattering waveform in impact-parameter
space.

16:40 → 17:00 Wrap up / Q&A: Q&A

Tuesday 20 January

10:00 → 10:50 Thibault Damour: Radiative Losses and Radiation Reaction in the Effective One-Body Approach: EOB, PN, MPM, PM, TF and All That

Abstract: A review will be presented of the radiative effects in the EOB approach as
obtained by combining information from various approximation methods, and
notably: the PN-matched Multipolar Post-Minkowskian formalism, the Post-
Minkowskian approach and the (EOB-based) Tutti Frutti approach.

10:50 → 11:00 Break

11:00 → 11:30 Piero Rettegno: Introduction to EOB formalism

Abstract: This talk will review the theoretical foundations of the EOB approach, describing
the first derivation of the EOB Hamiltonian, and showing how to include radiation
reaction effects by exploiting results from post-Newtonian theory.

Presentation_Pierro_Rettegno.pdf

11:30 → 11:45 Break

11:45 → 12:15 Piero Rettegno: Introduction to EOB formalism

Abstract: This talk will review the theoretical foundations of the EOB approach, describing
the first derivation of the EOB Hamiltonian, and showing how to include radiation
reaction effects by exploiting results from post-Newtonian theory.

12:15 → 12:40 Q&A Session

12:40 → 14:00 Lunch Break

14:00 → 14:30 Simone Albanesi: Hands-on session: a practical introduction to EOB softwares

Abstract: In this hands-on session we discuss the structure of EOB codes, focusing in
particular on TEOBResumS. We show how existing implementations can be used to
compute physical observables, such as waveforms and fluxes. The session
focuses on TEOBResumS-Dalí, the version of the code fore generic
orbits, providing practical examples illustrating its usage.

Presentation_Simone_Albanesi.pdf

14:30 → 14:45 Break

14:45 → 15:05 Simone Albanesi: Hands-on session: a practical introduction to EOB softwares

Abstract: In this hands-on session we discuss the structure of EOB codes, focusing in
particular on TEOBResumS. We show how existing implementations can be used to
compute physical observables, such as waveforms and fluxes. The session
focuses on TEOBResumS-Dalí, the version of the code fore generic
orbits, providing practical examples illustrating its usage.

Presentation_Simone_Albanesi.pdf

15:05 → 15:15 Break

15:15 → 16:00 Aldo Gamboa: The eccentric radiation-reaction force within the effective-one-body formalism

Abstract: Within the effective-one-body (EOB) formalism, the losses of energy and angular
momentum of a binary due to the emission of gravitational waves (GWs) are
modeled through a radiation-reaction (RR) force entering the
EOB equations of motion.
An accurate prescription for the EOB RR force is crucial, as it directly
determines the phase evolution of the binary, to which GW detectors are
particularly sensitive.
Inaccuracies in the RR force can therefore lead to systematic biases in the
estimation of the source parameters.
In this talk, I will describe how post-Newtonian results for the energy and
angular momentum fluxes are used, via flux-balance laws, to construct an
EOB radiation-reaction force, and I will discuss the additional difficulties that
arise when considering binaries on generic (non-circular) orbits.
I will then explain how these results are resummed and incorporated into
state-of-the-art EOB waveform models for eccentric binaries.
Finally, I will comment on the challenges involved in comparing different
eccentric waveform models, particularly in relation to eccentric numericalrelativity
simulations.

Presentation_Aldo_Gamboa.pdf

16:00 → 16:10 Break

16:10 → 16:40 Lorenzo Pompili: Effective-one-body waveforms and fluxes in Einstein-scalar-Gauss-Bonnet gravity

Abstract: Gravitational waves from coalescing compact binaries provide a unique
opportunity to test General Relativity (GR) in the highly dynamical, strong-field
regime. So far, most tests of GR with gravitational-wave signals have followed
parametrized, theory-independent approaches. An alternative avenue consists in
developing inspiral-merger-ringdown (IMR) waveform models in specific beyond-
GR theories by combining analytical and numerical-relativity results. In this talk,
we focus on Einstein-scalar-Gauss-Bonnet (ESGB) gravity, a theory which has
attracted particular attention due to its rich phenomenology for binary black-hole
mergers arising from nontrivial scalar fields. We discuss how to include ESGB
corrections to the resummed gravitational wave modes and energy fluxes for
quasicircular binaries within the effective-one-body (EOB) formalism. Key
modifications from GR include: (1) ESGB corrections to the metric modes through
2PN order, resummed using a factorization scheme inspired by GR; (2) an
additional scalar flux entering at relative -1PN order (dipolar radiation) and
extending through 2.5PN order. We also briefly discuss ESGB corrections to the
conservative dynamics (3PN Hamiltonian) and merger-ringdown waveform (quasinormal-
mode frequencies and remnant mass and spin). Combining these
ingredients, we provide the first complete IMR waveform model in a beyond-GR
theory and discuss the resulting waveform phenomenology. Finally, we present
constraints on the fundamental ESGB coupling from recent gravitational-wave
observations.

Presentation_Lorenzo_Pompili.pdf

16:40 → 17:00 Wrap up / Q&A

Wednesday 21 January

10:00 → 10:30 Thomas Osburn: Introduction to black hole perturbation theory and self-force methods

Abstract: The four main approaches to the relativistic two-body problem of general
relativity, numerical relativity (NR), post-Newtonian expansions (PN), post-
Minkowskian expansions (PM), and black hole perturbation theory (BHPT), each
have unique advantages and disadvantages, with effective one-body theory (EOB)
assembling results from each within their respective domains of validity. When
extreme mass-ratio inspirals (EMRIs) enter the strong field regime, BHPT is
necessary to build accurate gravitational wave models. This talk is an introduction
to BHPT in the context of gravitational wave source modeling for an audience
familiar with the basics of gravitational physics. The topics covered include 1)
expanding the Einstein field equations in powers of the mass-ratio, 2) formulating
the field equations in terms of either metric perturbations or Weyl scalars and the
Teukolsky equation, 3) considering how the small body's motion is influenced by
interactions with its own first-order field through the first-order self-force, and 4)
introducing second-order perturbations and associated challenges.

Presentation_Thomas_Osburn.pdf

10:30 → 10:45 Break

10:45 → 11:15 Thomas Osburn: Introduction to black hole perturbation theory and self-force methods

Abstract: The four main approaches to the relativistic two-body problem of general
relativity, numerical relativity (NR), post-Newtonian expansions (PN), post-
Minkowskian expansions (PM), and black hole perturbation theory (BHPT), each
have unique advantages and disadvantages, with effective one-body theory (EOB)
assembling results from each within their respective domains of validity. When
extreme mass-ratio inspirals (EMRIs) enter the strong field regime, BHPT is
necessary to build accurate gravitational wave models. This talk is an introduction
to BHPT in the context of gravitational wave source modeling for an audience
familiar with the basics of gravitational physics. The topics covered include 1)
expanding the Einstein field equations in powers of the mass-ratio, 2) formulating
the field equations in terms of either metric perturbations or Weyl scalars and the
Teukolsky equation, 3) considering how the small body's motion is influenced by
interactions with its own first-order field through the first-order self-force, and 4)
introducing second-order perturbations and associated challenges.

11:15 → 11:40 Q&A Session

11:40 → 11:50 Break

11:50 → 12:40 Adam Pound: State of the art in self-force theory

Abstract: In recent years, gravitational self-force theory has matured into a practical method of constructing fast, accurate, first-principles waveform models. In this talk, I summarize the state of the art in this approach to waveform modeling. I also highlight how synergies with other methods can overcome roadblocks in achieving beyond-leading-order, "post-adiabatic" accuracy across the parameter space of realistic binary configurations.

Presentation_Adam_Pound.pdf

12:40 → 14:00 Lunch Break

14:00 → 14:30 Zachary Nasipak: Computing GW fluxes and waveforms from self-force theory: a practical coding tutorial

Abstract: This tutorial provides a hands-on introduction to computing leading-order selfforce
fluxes and gravitational waveforms. Participants will work with two opensource
libraries—the Mathematica-based Black Hole Perturbation Toolkit and the
Python-based pybhpt—to generate fluxes and waveforms for quasi-circular and
eccentric binaries. (It is recommended that participants either have Jupyter/Python
and Mathematica installed on their machine or access to Google Collab and
Wolfram Cloud, if they wish to run the notebooks during the tutorial.)

LostInTranslation_SF_Fluxes_Tutorial.ipynb

LostInTranslation_SF_Fluxes_Tutorial.nb

14:30 → 14:45 Break

14:45 → 15:15 Zachary Nasipak: Computing GW fluxes and waveforms from self-force theory: a practical coding tutorial

Abstract: This tutorial provides a hands-on introduction to computing leading-order selfforce
fluxes and gravitational waveforms. Participants will work with two opensource
libraries—the Mathematica-based Black Hole Perturbation Toolkit and the
Python-based pybhpt—to generate fluxes and waveforms for quasi-circular and
eccentric binaries. (It is recommended that participants either have Jupyter/Python
and Mathematica installed on their machine or access to Google Collab and
Wolfram Cloud, if they wish to run the notebooks during the tutorial.)

15:15 → 15:30 Break

15:30 → 16:00 Kevin Cunningham: First Steps: Constructing First Order Metric Perturbations for Self-Force

Abstract: The speakers before me have introduced the EMRI problem, and the
perturbative and multi-scale techniques that we use to solve the problem.
One key consideration is that we need to go to second order in our perturbative
expansion in order to model EMRIs well enough to achieve the LISA mission's
science goals. Constructing the second order self-force requires accurate first
order information, in a suitable gauge. In this talk I will talk a little about
techniques that have been used in the past to calculate first order metric
perturbations, and about some modern techniques being used, including my own
work constructing Lorenz gauge metric perturbations in Lorenz gauge through
metric reconstruction, using recent breakthrough by Wardell, Kavanagh and
Dolan.

Presentation_Kevin_Cunningham.pdf

16:00 → 16:10 Break

16:10 → 16:40 Philip Lynch: Efficient Eccentric Effective-One-Body Dynamics via Near-Identity Averaging Transformations

Abstract: Next-generation gravitational wave detectors, such as LISA, the Einstein
Telescope, and Cosmic Explorer, will require accurate modelling of long-lived black
hole binary signals, including those with orbital eccentricity. A major challenge in
using eccentric effective-one-body (EOB) models for parameter estimation is the
high computational cost of evolving long-lived eccentric dynamics. We address this
by first recasting the EOB equations of motion using the method of osculating
orbital elements and then applying near-identity averaging transformations during
the inspiral phase.
By implementing these transformations up to second post-adiabatic order, we obtain
averaged equations of motion that faithfully capture the long-term dynamics of
comparable-mass systems. This approach eliminates the need to resolve rapidly
oscillating orbital dynamics, reducing the cost of the dynamics by a factor of the
mass ratio and reducing the overall cost of waveform generation even for
comparable mass systems.

Presentation_Philip_Lynch.pdf

16:40 → 17:00 Wrap up / Q&A