Name: Frederik Orellana (email_not_shown)
Date: 06/27/02-03:05:03 PM Z


Hello.

First of all, don't usually expect to get anything reasonable out of
factors with more than two occurrences of the same index. FeynCalc assumes
the usual Einstein summation convention, but cannot judge what to do in
cases like x*x.

Try

x=LC[a,b,c,d]FourVector[k1,a]FourVector[k2,b]FourVector[k3,c]FourVector[k4,d];
y=LC[e,f,g,h]FourVector[k1,e]FourVector[k2,f]FourVector[k3,g]FourVector[k4,h];
x y // Contract

W.r.t. writing out x in terms of scalar products, this would amount to
writing out the Levi-Civita tensor in terms of Kronecker deltas. I don't
believe this is possible?

Regards, Frederik Orellana

At 15:41 20-06-2002 +0200, you wrote:
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>Hello,
>
> I'm using version 4.1.1 on Mathematica 4.0.
> The problem arises when I have the following expression:
>
>x=LC[a,b,c,d]FourVector[k1,a]FourVector[k2,b]FourVector[k3,c]FourVector[k4,d]
>
> I have previously given the value of all possible scalar products. I want
>Feyncalc to expand x using these scalar products.
> I've tried to use every possible Feyncalc command, without success. On the
>other hand, if I ask it to compute Calc[x*x], it works! I've checked by hand,
>the result is correct, but then I loose the sign of x.
> Is there a way to make Feyncalc expand a single LC contraction? Is it a
> bug?
> Regards,
>
>- --
>Thibaut Cousin
>email : cousin@in2p3.fr
>web : http://clrwww.in2p3.fr
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