Friday, March 13th 2026
10.30 – 15.30 followed by drinks

Lorenz Eberhardt (UvA)
Maria Ubiali (Cambridge) – Nikhef Colloquium
Béatrice Bonga (RU)
Oksana Iarygina (Nordita)

Lorenz Eberhardt (UvA) – How string theory computes quantum gravity amplitudes 
Abstract: String theory provides a framework in which quantum gravitational scattering amplitudes are ultraviolet finite and computable in perturbation theory. These amplitudes are defined by integrating over the moduli space of Riemann surfaces, replacing the Feynman diagram expansion of field theory by a sum over worldsheet topologies. I will review how this definition arises and explain structural properties such as UV-finiteness, dual resonance and their Regge behavior. I will then discuss recent progress in explicit computations, focusing on one-loop amplitudes and new results on their high-energy behavior.

Maria Ubiali (Cambridge) – Precision Physics at the LHC and Beyond
Abstract: The unprecedented precision achieved by the Large Hadron Collider (LHC) has transformed hadron collider physics into a high-precision laboratory for testing the Standard Model (SM) and probing new physics. In this regime, theoretical uncertainties play an increasingly central role.
In this talk, I will discuss recent developments in theoretical predictions at the LHC, with particular emphasis on parton distribution functions (PDFs), which parametrize the subnuclear structure of the proton. I will describe their impact on precision phenomenology and searches for physics beyond the Standard Model (BSM) and show how modern statistical and machine learning techniques enable a flexible and robust determination of PDFs from global collider data. I will also focus on the interplay between proton structure and new physics searches, showing how standard PDF fitting procedures may partially absorb or distort potential signals in high-energy observables.
Finally, I will outline a program towards a fully Bayesian analysis of PDFs and SM and BSM parameters. This approach provides improved control over prior assumptions and consistently incorporates correlations among intrinsically connected quantities. Such a unified framework is essential for fully exploiting current LHC data and for preparing for the precision frontier of the High-Luminosity LHC and future colliders.

Béatrice Bonga (RU) – the Messy Reality of Gravitational Wave Ringdowns 
Abstract: The past decade has completely transformed our understanding of what happens after black holes collide. What we once thought could be well-described by simple ringdowns—neat linear combinations of damped sinusoids (quasi-normal modes)—have turned out to be far richer and messier. Today we recognize ringdowns as an intricate tapestry woven from these quasinormal modes, nonlinear effects, tails, and secular phenomena like gravitational memory. In this talk, I’ll dive into the nonlinear aspects: where the theory stands today and some exciting recent observational claims that we might already be seeing these effects in GW250114.

Oksana Iarygina (Nordita) – Gravitational Waves and Magnetic Fields from Axion Inflation
Abstract: In the coming years, the search for primordial gravitational waves will combine direct detection with space-based observatories and measurements of Cosmic Microwave Background B-mode polarization. Accurately interpreting these measurements depends heavily on understanding their production mechanisms. A particularly compelling scenario involves gravitational wave generation through the interaction of an axion with gauge fields during inflation. I will present recent advances in axion inflation with non-Abelian gauge fields, focusing on the signatures in the primordial gravitational wave background and their correlation with primordial magnetic fields. I will also discuss how the emergence of a primordial plasma via the Schwinger effect alters the early universe dynamics, modifying both the gravitational wave signal and primordial magnetic field predictions.

Nikhef colloquium room, Nikhef, Science Park 105, Amsterdam

A zoom connection is available for those that wish to join remotely: https://go.nikhef.nl/colloquium

For questions or suggestions, please contact one of the organizers:

Melissa van Beekveld (NIKHEF)
e-mail: mbeekvel@nikhef.nl

Timothy Budd (RU)
e-mail: T.Budd@science.ru.nl

Subodh Patil (UL)
e-mail: patil@lorentz.leidenuniv.nl