Name: Vladyslav Shtabovenko (email_not_shown)
Date: 05/12/14-10:08:04 AM Z


Hi,

> Before we load Feyncalc and Feynarts, all is ok:
> Conjugate[Exp[i*Pi/4]]=Exp[-i*Pi/4](Normal),
> but when the packages(Feyncalc and Feynarts) are both loaded, I find
this BUG appear:
> Conjugate[Exp[i*Pi/4]]=Exp[i*Pi/4](BUG!).
> when I set $LoadPhi=False and $LoadFeynArts=False
> and execute <<HighEnergyPhysics`FeynCalc`,this time I only load
FeynCalc, I find this BUG disappear again:
> Conjugate[Exp[i*Pi/4]]=Exp[-i*Pi/4](Normal).

The problem is that in the present state (at least in Mathematica 9)
FeynArts and Phi don't really work with FeynCalc. When you load them
nevertheless, you get a bunch of error messages related to shadowing.

As you correctly observed, using

$LoadPhi=False
$LoadFeynArts=False
<<HighEnergyPhysics`FeynCalc`

avoids these problems.

> Another question is:
> when use "ComplexConjugate" to replace "Conjugate" I find another question.
> ComplexConjugate[Exp[i*Pi/4]]=Exp[-i*Pi/4](Normal)
> ComplexConjugate[5^i]=5^i(BUG?)
> please contact me soon!
> Email:qfsun@mail.ustc.edu.cn
> Thank you!
>

I think that this behavior of ComplexConjugate is not a bug. The
description of the command (?ComplexConjugate) says
---------------------------------------------------------
ComplexConjugate[expr] complex conjugates expr.
It operates on Fermion-lines, i.e., products
of Spinor[..] .DiracMatrix[..] . Spinor[..].
For taking the spin sum (i.e. constructing the traces) use
FermionSpinSum.

WARNING: In expr should be NO explicit I in denominators!
---------------------------------------------------------

Now if you apply ComplexConjugate to 5^I, you are explicitly
ignoring the warning, which is why you are getting a wrong result.

I would not use ComplexConjugate for anything that is not a fermion line
or contains explicit I's.

Cheers,
Vladyslav



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