What's new (2020)

New article related to Qgraf–r is available online (paper ‘III’ listed below).

latest version:  1.0

Qgraf–r can compute particle number conservation rules (both additive and multiplicative) for many types of QFT models. It is then able to identify (un)physical processes that break those rules, thereby ruling out the existence of matching Feynman diagrams for every order of perturbation theory.

Additionally, qgraf–r can ‘solve’ inclusive processes with a fixed number of external fields, some of which ‘unknowns’ — that is, it can find the matching non-inclusive processes that satisfy the number conservation rules it has itself computed. For example, it can create a list of the n–point functions allowed by those rules (for n fixed, and not too large).

The information produced by qgraf–r may also be used to partly cross-check the input model-file. For instance, if some of the rules of the (intended) model are known in advance, and if they are not compatible with those computed by the program, then the model description is very likely incorrect.

  • Latest version: qgraf–r–1.0 (2019).
    Please report any error you may happen to find.

  • Programming language: Fortran.
    No binaries either (see also the corresponding entry for qgraf).

Most of the theory behind qgraf–r is described in these articles:

  • From Feynman rules to conserved quantum numbers, I
    P. Nogueira
    Comput. Phys. Commun. 214 (2017) 83–90

  • From Feynman rules to conserved quantum numbers, II
    P. Nogueira
    Comput. Phys. Commun. 215 (2017) 13–19

  • From Feynman rules to conserved quantum numbers, III
    P. Nogueira
    Comput. Phys. Commun. 260 (2021) 107740
    (published online 10 December 2020)