Numerical Perturbation Theory

Session

Morning 1

20 Nov 2025, 09:00

E41.1 (ETHZ)

3. Applications and challenges in numerical methods for pQFT

Valentin Jonathan Hirschi (University of Bern)

20/11/2025, 09:00

I will briefly present a [recent application][1] of [Local Unitarity][2] to the calculation of the NNLO QCD correction to $\gamma \gamma \rightarrow Q \bar{Q}$.

Local Unitarity is a computational technique achieving the local cancellation of infrared singularities at the integrand level, unlocking the computation of perturbative cross-section fully numerically in momentum space.

This...

5. The art of constucting and sampling cut integrals

Mathijs Fraaije (University of Bern)

20/11/2025, 09:25

This talk will introduce new Monte Carlo sampling techniques used for the numerical integration of momentum-space loop integrals in the Loop-Tree Duality (LTD) framework.

I will then discuss the factorization property of the Cross-Free-Family (CFF) representation of LTD and how it can be used to conveniently construct three-dimensional integrands of cut diagrams.

4. Localized renormalization and graph-based tooling

Lucien Huber (University of Bern)

20/11/2025, 09:50

The BPHZ formalism provides a systematic framework for subtracting ultraviolet divergences from Feynman graphs. Originally conceived as a purely theoretical construct, it now underpins the ultraviolet regularization strategy for Local Unitarity, as implemented in gammaloop, an upcoming program designed to compute perturbative cross-sections fully numerically in momentum space.

In this talk,...