Name: Pedro Ruiz-Femenia (email_not_shown)
Date: 02/02/17-08:41:39 PM Z


Hi Vladyslav,

thanks a lot for the detailed answer.

>As to the second part of your question, the issue here is, that, in >general, Larin's scheme doesn't allow one to anticommute gamma^5 >matrices in a trace with an even number of gamma^5. I know that this >is what people usually do in QCD calculations and in most cases this >works out as it should, but nevertheless this trick is not >guaranteed to give correct results in all cases.

I am not very familiar with Larin's scheme, but I would have naively expected that any gamma5 scheme gives the same output for traces with an even number of gamma5's, even if the anticommutation of gamma5 is not allowed in such a scheme. But from what you are saying it seems this is not true, right?

>On the other hand, I'm always in favor of giving people the right to
>choose how they do their calculations, as long as they understand the
>implications. In my view the only acceptable solution here is to
>implement a second Larin's scheme with the property that you >request, so that traces with an even number of g^5 will give the >same result as in NDR.

I think it makes sense, since for traces with even number of gamma5's one does not usually bother about gamma5 issues (modulo some subtlety related to your comment above (?)).

>In fact, this is probably also a good point to improve the way how
>traces are calculated in Larin's scheme, as the current performance >is apparently very bad.

Indeed: I am not sure if it is a problem of Larin's scheme only, but the time needed to compute a trace that has a factor

cv GAD[mu] + ca GAD[mu].GA[5]

inside, is very much reduced is one writes the trace as two separate traces, one with the vector and one with the axial-vector piece.

>The only issue is that I quite busy at the moment, so it will take me
>some time O(2-3 weeks) to take care of that.

That's perfectly ok, there is no hurry!

Thanks again,
Pedro

Cheers,
Vladyslav



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