Numerical Perturbation Theory

Session

Afternoon 1

20 Nov 2025, 13:30

E41.1 (ETHZ)

1. Factorisable Local Unitarity for Hadronic Cross-Sections

Zeno Capatti (University of Bern)

20/11/2025, 13:30

The KLN theorem establishes that infrared divergences in parton‑model diagrams cancel when summed alongside diagrams that account for the simultaneous hard interaction of multiple partons within the same hadron. Meanwhile, it is well established that initial-state infrared poles and logarithms are governed by collinear factorisation. In this talk, I introduce a formalism where an initial-state...

6. Loop–Tree Duality at Finite Temperature and Density

Kaapo Elmo Ilmari Seppänen (University of Bern)

20/11/2025, 13:55

In finite-temperature or finite-density QFT, computing perturbative coefficients is notoriously challenging because the thermal bath breaks Lorentz symmetry by singling out the time direction, making standard integration-by-parts and differential-equation techniques inefficient. I will present the generalization of Loop–Tree Duality (LTD) to thermal settings, in which loop-energy (Matsubara)...

15. Soft Factorisation and Exponentiation from Schwinger-Space Geometry

Giulio Gambuti (University of Oxford)

20/11/2025, 14:20

In this talk I will report on a recent analysis of soft divergences of entire scattering amplitudes within the Schwinger-parameter representation of Feynman integrals. Using tools from tropical geometry and graph theory, I will show how soft and hard contributions factorise directly in parameter space and how “worldline” Schwinger variables make exponentiation of soft divergences manifest at...