Loops without loops and the Feynman tree

by German Rodrigo Garcia (IFIC Valencia)

Thursday 11 Apr 2019, 14:00 → 15:00 Europe/Zurich

Aula Caldirola (Dipartimento di Fisica, Università degli Studi di Milano)

Quantum field theory is poorly defined in four space-time dimensions 
due to unphysical configurations introduced by quantum corrections. 
These unphysical configurations lead to the proliferation of 
infinities that are usually regulated by modifying the dimensions of 
the space-time. In this talk we introduce the loop-tree duality (LTD) 
and the four-dimensional unsubtraction (FDU) formalisms.
The LTD allows to rewrite loop scattering amplitudes in terms of 
connected tree-level dual amplitudes, and provides a very intuitive 
view over the origin of the IR and UV singularities and their 
interpretation in terms of causality.  We also comment on its relation 
to the Feynman’s Tree Theorem. The FDU allows to perform the summation 
over soft and collinear degenerate states from virtual and real 
configurations by introducing a suitable mapping of momenta, then 
avoiding subtractions in the infrared in such a way that higher order 
perturbative calculations can directly be performed in four space-time 
dimensions. We illustrate the power of the formalism with benchmark 
physical examples.

2019_04_rodrigo_Milano.pdf