feynlag.export.ufo.vvvv.permute_vvvv¶

feynlag.export.ufo.vvvv.permute_vvvv(structures, perm, simplifier=<function simplify>)[source]¶

Structures after relabelling the external legs by perm.

Parameters:

structures – {VVVV1/2/3: coeff} for the current leg order.
perm – a 4-tuple mapping input leg n to result leg perm[n] (0-based). Every current caller passes an involution, for which the direction is immaterial; a 3- or 4-cycle would not be.

A permutation mixes the catalog structures (swapping legs 2 and 3 sends VVVV1 <-> VVVV2 and flips VVVV3), so callers that need a partner ordering – the hermiticity check, or matching MadGraph’s leg order – must go through here rather than reusing the coefficients verbatim.