**Next message:**Rolf Mertig: "Re: Frustrating problem with Tr[0.]"**Previous message:**Rolf Mertig: "Re: Tr and Calc"**Next in thread:**Rolf Mertig: "Re: Frustrating problem with Tr[0.]"**Reply:**Rolf Mertig: "Re: Frustrating problem with Tr[0.]"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]**Mail actions:**[ respond to this message ] [ mail a new topic ]

Hello,

I am using fc5beta2 with Mathematica 5.2 both on MacOsX 10.4. There is a small but very frustrating problem when one runs Tr[0.*GS[p]]

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In[1]:=

<<HighEnergyPhysics`FeynCalc`

In[2]:=

Tr[DiracSimplify[0.*GS[p]]]

*>From In[2]:=
*

\!\(\*FormBox[

RowBox[{\(Power::"infy"\), \(\(:\)\(\ \)\), "\<\"Infinite expression \\!\\(

TraditionalForm\\`1\\/0.`\\)

encountered. \\!\\(\\*ButtonBox[\\\"More…\\\", \

ButtonStyle->\\\"RefGuideLinkText\\\", ButtonFrame->None, \

ButtonData:>\\\"Power::infy\\\"]\\)\"\>"}], TraditionalForm]\)

*>From In[2]:=
*

\!\(\*FormBox[

RowBox[{\(∞::"indet"\), \(\(:\)\(\ \)\), "\<\"Indeterminate

expression \\!\\n\\(

TraditionalForm\\`\\(0.`\\\\ \

\\(\\(\\(\\(TraditionalForm\\`\\\"\\\\[Gamma]\\\"\\)\\) · \

\\(\\(TraditionalForm\\`p\\)\\)\\)\\)\\\\ ComplexInfinity\\)\\)\\n \

encountered. \\!\\(\\*ButtonBox[\\\"More…\\\", \

ButtonStyle->\\\"RefGuideLinkText\\\", ButtonFrame->None, \

ButtonData:>\\\"General::indet\\\"]\\)\"\>"}], TraditionalForm]\)

Out[2]=

Indeterminate

----------------------------------

The exchange to tr = TR[Calc[#]]&; doesn't help. Expressions multiplied by "real" 0 occur in processing large expressions involving lots of terms, so it would be extremely hard to hunt all instances of 0. which occur as cancellations of terms with "real" coefficients like 0.5*GS[p]-0.5*GS[p]. Is there an easy way to get rid of this annoying error and get the correct answer for Tr[0.]=0?

One more question, why Tr[0] doesn't return 0?

-- Best Regards: Hrayr

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