Counting to one: reducibility of one- and two-loop amplitudes at the integrand level

Understand

Calculation of amplitudes in perturbative quantum field theory involve large loop integrals.

• The complexity of those integrals, in combination with the large number of Feynman diagrams, make the calculations very difficult.
• Reduction methods proved to be very helpful, lowering the number of integrals that need to be actually calculated.
• Especially, the reduction at the integrand level technique, improves the speed and set-up of these calculations.