FCGetFreeIndices[exp, {head1, head2, ...}] returns the
list of free (uncontracted) indices from heads head1,
head2, …
As always in FeynCalc, Einstein summation convention is implicitly
assumed. The function is optimized for large expressions, i.e. it is not
so good as a criterion in e.g. Select.
If it is understood that each term in the expression contains the
same number of free indices, setting the option First to
True can considerably speed up the evaluation.
Overview, FCRenameDummyIndices, Contract, FCGetDummyIndices, DummyIndexFreeQ, FreeIndexFreeQ.
FCI[FV[p, \[Mu]] FV[q, \[Nu]]]
FCGetFreeIndices[%, {LorentzIndex}]\overline{p}^{\mu } \overline{q}^{\nu }
\{\mu ,\nu \}
FCI[FV[p, \[Mu]] FV[q, \[Mu]]]
FCGetFreeIndices[%, {LorentzIndex}]\overline{p}^{\mu } \overline{q}^{\mu }
\{\}
FCI[SUNT[a, b]]
FCGetFreeIndices[%, {SUNIndex}]T^a.T^b
\{a,b\}
FCI[SUNT[a, a]]
FCGetFreeIndices[%, {SUNIndex}]T^a.T^a
\{\}