Name: V. Shtabovenko (email_not_shown)
Date: 04/21/18-02:55:55 PM Z

Hi,

I'm not sure that I exactly understand what you are trying to achieve,
so an explicit example (preferably in the FeynCalc notation) would be
helpful.

Did you already have a look at various FCLoop* functions, cf. Section
3.4 of arXiv:1601.01167 ?

exp = FVD[q1 + l, mu] FVD[q2 + l, nu] FVD[l,
rho] FAD[{l}, {l + q1}, {l + q2}];

FCLoopIsolate[exp // ExpandScalarProduct, {l}]

I'm also not sure that I understand what are tensor integrals that
cannot be handled using tensor reduction.

As long as your integrals depend on some 4-momenta (loop and external),
like f(q_i,l_i), it should be possible to use the Tdec function and
generate the tensor basis, independently of what f(q_i,l_i) looks like.

For example, in my PhD thesis I used Tdec to do tensor reduction on
nonrelativistic Cartesian integrals and that worked flawlessly (albeit
with some amount of extra code).

Cheers,
Vladyslav

Am 21.04.2018 um 00:16 schrieb Matt Rizik:
> Hi,
>
> I'm linking my question from Stack Exchange for clarity, since I can use TeX formatting there:
>
> https://mathematica.stackexchange.com/questions/171476/is-there-a-method-in-feyncalc-for-collecting-like-powers-of-four-vectors
>
> My problem concerns isolating like powers of some loop momentum in order that a large integral may be broken down into a sum over smaller integrals without using PV reduction. Is there any built-in method to do this?
>
> Thanks in advance!
>
> -Matt
>

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