Local Unitarity

TL;DR

The paper introduces Local Unitarity, a formalism that rewrites cross-sections to cancel infrared singularities locally, simplifying calculations and enabling more efficient Monte Carlo integration for quantum field theory observables.

Contribution

It presents a novel Local Unitarity approach that regulates infrared divergences locally, eliminating the need for counter-terms and facilitating automation in fixed-order computations.

Findings

Infrared singularities are canceled locally within the formalism.

The method simplifies phase-space and loop integral regulation.

It enhances the automation of fixed-order differential observable calculations.

Abstract

Within the Local Unitarity formalism, any physical cross-section is re-written in such a way that cancellations of infrared singularities between real and virtual contributions are realised locally. Consequently, phase-space and loop integrals are regulated locally without the need of any counter-terms or dimensional regularisation aside from those strictly needed to achieve ultraviolet regularisation. This Local Unitarity representation is especially suitable to direct Monte Carlo integration. As such, it offers a clear and direct path to automate the computation of fixed-order differential observables in Quantum Field Theories.