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I am trying to simplify a rather complicated equation involving vectors and kronecker delta. I am trying to use Feyncalc for this purpose, but somehow i am not able to do it using Contract/Trick.

Could some one help me ?

A simple thing like KroneckerDelta[u,v] FV[x,v] is also not giving be the desired result.

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You are mixing things that don't belong together. KroneckerDelta is a built-in Mathematica object, while FV is FeynCalc's shortcut for a Lorentz 4-vector. FeynCalc's Contract naturally works only with FeynCalc objects.

If you want to use FeynCalc for your purposes, you should write MT[u,v] instead. Since FeynCalc doesn't distinguish between upper and lower Lorentz indices, Kronecker delta and Minkowski metric are essentially represented by the same object.

Contract[MT[u, v] FV[x, v]]

returns the correct result.

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  • $\begingroup$ Great catch; +1 $\endgroup$
    – Sektor
    Commented Apr 20, 2015 at 10:29

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