Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

FeynCalc Mathematica : Polarization Vector Sum

  1. Dec 22, 2009 #1

    Hepth

    User Avatar
    Gold Member

    Does anyone here use Feyncalc? (Or have a better alternative).

    I have terms that I need to simplify like :

    (2 Pair[Momentum[p1], Momentum[PB]] Pair[Momentum[p2],
    Momentum[Polarization[q, -I]]] Pair[Momentum[PB],
    Momentum[Polarization[q, I]]])/(
    Pair[Momentum[p1], Momentum[q]] Pair[Momentum[p2], Momentum[q]])

    Which looks like :
    [tex]
    \frac{(p1\cdot \varepsilon (q) )( p2\cdot \varepsilon^{*}(q))}{(p1 \cdot q)}
    [/tex]

    Everything is general 4-vectors, the polarizations also. Now this, by hand, is easily simplified by doing a polarization sum. The top is just -p1.p2, as the sum gives the negative metric tensor. I can't seem to do this in FeynCalc though. If you use "PolarizationSum[m,n]" itll just spit out the negative metric tensor, but the indices of p1,p2 and epsilon are all INTERNAL, so that [m,n], is actually something internal that I cannot specify.

    Has anyone done something like this before? Or do you have an alternative program?
     
  2. jcsd
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Can you offer guidance or do you also need help?
Draft saved Draft deleted