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Institute for Particle Physics Phenomenology

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Institute for Particle Physics Phenomenology

Description: 

Title:

Manifestly Causal Scattering Amplitudes

 

Abstract:

The numerical evaluation of multi-loop scattering amplitudes in the Feynman representation usually requires to deal with both physical (causal) and unphysical (non-causal) singularities. The loop-tree duality offers a powerful framework to easily characterise and distinguish these two types of singularities, and then simplify analytically the underling expressions. In this talk, we explicitly discuss the dual representation of multi-loop Feynman integrals generated from five parent topologies, which we refer to as Next-to-…-Next-to-Maximal loop topologies.  In particular, we aim at expressing these dual contributions, independently of the number of loops and internal configurations, in terms of causal propagators only. Thus, providing very compact and causal integrand representations to all orders.  In order to do so, we reconstruct their analytic expressions from numerical evaluation over finite fields. This procedure implicitly cancels out all unphysical singularities. We also interpret the result in terms of entangled causal thresholds. In view of the simple structure of the dual expressions, we integrate them numerically up to four loops in integer space-time dimensions, taking advantage of their smooth behaviour at integrand level.

 

Zoom link:  IPPP Seminars

https://durhamuniversity.zoom.us/j/99420124988?pwd=ZEFLSDB3THJtaWZOTU54R25mT1NuZz09

Type: 
Lecture
Category: 
Oct 2020 - Sept 2021
Date: 
05/11/2020
Timezone: 
Europe/London
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