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+1 vote

when I use

ex:=A A tr{u^{\mu} u^{\nu}} tr{u^{\nu} u^{\mu}}- B B tr{u^{\mu} u^{\nu}} tr{u^{\mu} u^{\nu}};

I get the following error

{\color{red}{\begin{verbatim}RuntimeError: Power with free indices not allowed.

At: (4): \end{verbatim}}}

How to solve it?

in General questions by (2.1k points)

1 Answer

+1 vote
Best answer

Now fixed on github. The problem was that collect_factors would try to collect the trace expressions because it didn't correctly scan for free indices on those factors.

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