Name: V. Shtabovenko Date: 02/18/19-04:20:17 AM Z
Am 15.02.19 um 16:17 schrieb Mao Zeng:
> Does FeynCalc have capabilities to contract gamma matrices with
explicit spinor indices? For example, if I have an expression like
> GA[mu][i, j] GA[nu][k, l]
GA[rho][j, k], can I use FeynCalc to transform the
expression into GA[mu] . GA[rho] . GA[nu]? The
nontrivial part is correct ordering of the gamma matrix chain, by
following the contraction of the indices (i, j, k, l) above. Similarly,
I’m wondering if FeynCalc can perform contraction of SU(N) color
matrices with explicit indices, something like SUNT[a][i,
j].
>
For SU(N) matrices this is available since FeynCalc 9.2, cf. Sec 3.7
of
1601.01167
For the Dirac matrices I remember pushing some initial code into the
dev
version some time ago, but that was not production ready and not
sufficiently tested.
> It shouldn’t be hard for me to program this myself, but before I start, I’d like to know if FeynCalc has any built-in functions to handle such index contractions, similar to what can be done by e.g. FormTracer (arXiv:1610.09331).
Well, if it is not hard for you, then do it, after all FeynCalc is all
about being extendalbe. BTW, FormTracer can be conveniently employed
to
process FeynCalc expressions and convert the results back into the
FeynCalc notation. I remember Anton Cyrol (one of the developers)
showing me several scripts for doing that were only few lines of extra
code where needed. You can ask him for details.
Cheers,
Vladyslav
>
> Thanks for the help!
>