Name: Vladyslav Shtabovenko Date: 04/05/14-09:40:34 PM Z

Dear all,

I would like to report two bugs I encountered in Feyncalc 8.2 (latest
version). I’m using Mathematica 9, but the bugs are not really related
to that.

First of all, in Models/FCQCDLorentz.gen there should be a
“$FermionLines = True” statement, since otherwise FeynArts generates
diagrams without Dirac traces and FeynCalc subsequently fails to compute
the color trace. This is fixed in Phi, but not in FeynCalc itself.

Then, in general/Collect3.m, there is a regression bug related to the
MonomialList function. In FC8.1 there was a condition to use the
FeynCalc’s version of MonomialList for Mathematica below version 6. For
some reason this condition was removed in FC8.2. The problem is, that
Mathematica’s built-in MonomialList doesn’t have the Option
“CoefficientDomain -> RationalFunctions”, which makes all functions that
rely on Collect3 fail.

You can easily reproduce the bugs by trying to run
fcexamples/qcdghostse2loopnew2.nb.
Because of the missing Dirac traces and the broken MonomialList, the
computation fails on FC8.2.

Please find the patch that fixes this problems attached.

Just in case, I also attach a patch for the FeynArts 3.7, since
automatic patching doesn’t seem to work with Mathematica 9. The patch is
just what happens to FA 3.7 after you run

<< “HighEnergyPhysics`Phi`Extras`FAPatch`”
$FeynArtsDirectory =
“/home/YOUR_USERNAME/.Mathematica/Applications/HighEnergyPhysics/FeynArts-3.7/”
HighEnergyPhysics`Phi`FAPatch`FAPatch[]

-————————————————————————
If you need to use FeynCalc 8.2 now and you absolutely cannot wait until
developers release the new version, here’s a quick fix guide on Linux:

1) Install fresh Feyncalc via
    Import[“http://www.feyncalc.org/install.m”]
2) Copy the attached patches to
~/.Mathematica/Applications/HighEnergyPhysics

3) In the console run
    cd ~/.Mathematica/Applications/HighEnergyPhysics
    patch -p0 < feynarts.patch
    patch -p0 < fc82.patch
4) Restart Mathematica, run fcexamples/qcdghostse2loopnew2.nb. and check
    that you get the same results as in the notebook
-———————————————————————-

P.S. Correct me if I’m wrong but it looks like in the CVS we still have
FC8.1, not FC8.2. Also, with the instructions on
http://www.feyncalc.org/cgi-bin/cvsweb.cgi/ it is impossible to check
out the repository :(

Cheers,
Vladyslav