Name: Sascha T. (email_not_shown)
Date: 08/12/08-07:21:29 PM Z


Hello,

I tried to find a general expression for a tensor integral using
Feyncalc. To test the result, I performed an especially easy
contraction where one can calculate the result by hand. Unfortunately
I reproduced the result only up to an additional summand of 1/2.

I then tried to find where I made a mistake. Finally I figured out
that there is obviously a problem with Feyncalc. Maybe it is related
to Bug #4, but it is somehow different.

Using the following mathematica code, the problem becomes obvious
already in this very simple case:

LoopFunc =
 FVD[q, \[Mu]] FVD[q, \[Nu]]
  FAD[{q, Subscript[m, 0]}, {q + Subscript[p, 1], Subscript[m, 1]}]

test1 =
 OneLoop[q,
  Contract[MTD[\[Mu], \[Nu]] LoopFunc ,
   OneLoopSimplify -> False] ]

test2 = Contract[
  MTD[\[Mu], \[Nu]] OneLoop[q, LoopFunc,
    OneLoopSimplify -> False] ]

diff = PaVeReduce[(test1 - test2)]

Can you please comment on this. Maybe it is already known. Or you can
advice me, what I should not do using these functions since I do not
know why this problem occurs.

best regards,
Sascha



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