**Next message:**zhangyaworld: "Eight Gamma Matrix involving Gamma5, within t'Hooft Scheme"**Previous message:**Matt Rizik: "Is there a method in FeynCalc for collecting like powers of four vectors? rizikmat@msu.edu"**In reply to:**Matt Rizik: "Is there a method in FeynCalc for collecting like powers of four vectors? rizikmat@msu.edu"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]**Mail actions:**[ respond to this message ] [ mail a new topic ]

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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