On the situation with SUNSimplify and SUNTrace

[vsht]

Dear FeynCalc users,

over the last years we received numerous complaints about SUNSimplify and SUNTrace either not being able to evaluate
some comparably simple expressions or producing weird results. So I took some time to rewrite the old legacy code and align
the working logic with other FeynCalc routines. The main changes are as follows

• SUNTrace will not evaluate anything unless the option SUNTraceEvaluate is set to True
• SUNSimplify also has the option SUNTraceEvaluate, but it is set to Automatic. This means that traces with 2 or 3 matrices are always evaluated, while those with more matrices will remain untouched (unless they can be simplified in other ways). Setting this option to True will force all traces to be evaluated.
• The option SUNIndexRename is gone, now indices will be canonicalized by default using FCCanonicalizeDummyIndices. You can specify the names of dummy indices via the options SUNIndexNames and SUNFIndexNames
• SUNFSimplify is gone for good, as SUNSimplify now has full support for explicit fundamental indices

The new code is already in the dev version and the documentation has been updated as well:

https://feyncalc.github.io/FeynCalcBookDev/SUNSimplify.html

https://feyncalc.github.io/FeynCalcBookDev/SUNTrace.html

It would be really nice if you could test it on expressions that didn't work that well with the old SUNSimplify and SUNTrace. Or perhaps let me know if things that used to work in the past are not working anymore. Since the new code is neat and clean, bugs should be comparably easy to fix now.

Cheers,
Vladyslav