Hi,
the question is not really related to FeynCalc, since CreateTopologies
is a FeynArts function. Anyway, you need to add more points to the
Adjacencies option:
?Adjacencies
Adjacencies is an option of CreateTopologies. Its setting is a list
{e1, e2, ...} of integers (ei > 2) of allowed adjacencies of vertices.
The adjacency of a vertex is the number of propagators ending at that
vertex. The two special cases ei = 1 and 2 are for external particles
and counter terms, respectively, and are taken care of by
CreateTopologies.
E.g.
top1 = CreateTopologies[0, 3 -> 3, Adjacencies -> {3, 4, 5, 6}]
Paint[top1, AutoEdit -> False]
I disabled the automatic call to the shaper, but at some point you might
still need to shape those topologies to make them look nice.
Cheers,
Vladyslav
Am 10.07.19 um 17:42 schrieb gghuen:
> Hi,
> I want to use FeynCalc to do some amplitude computation in Effective Field Theories. In particular, I am interested in higher points (𝑛>4) scattering amplitudes, that may receive contributions from pure contact terms. When I create the topology for tree-level 3->3 processes, the result does not contain the topology of a contact term. Instead, for a 2->2 process the contact term is considered in the TopologyList. You can easily see this with the following commands
>
> $LoadFeynArts = True;
> << FeynCalc`;
> $FAVerbose = 0;
> FAPatch[PatchModelsOnly -> True]
> top1 = CreateTopologies[0, 2 -> 2];
> Paint[top1]
>
> top2 = CreateTopologies[0, 3 -> 3];
> Paint[top2]
>
>
> Why contact terms of higher points amplitudes are not considered in the TopologyList? Indeed, when computing 6pt amplitudes, the 6pt contact terms of my model are not used while only 4pt contact terms are glued to make 6pt amplitudes.
>
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