Name: Vladyslav Shtabovenko (email_not_shown)
Date: 06/01/16-11:43:35 AM Z


Hi,

could you please provide a minimal sample code where this happens?

By default PaVeReduce should leave A0[m^2] or equivalently PaVe[0, {},
{m^2}] untouched, which is what I'm currently observing:

$LoadAddOns = {"FeynHelpers"};
<< FeynCalc`

A0[m^2] // PaVeReduce
PaVe[0, {}, {m^2}] // PaVeReduce

A0 of course can be converted to B0 via the option A0ToB0 of the
"direct" A0 function. Here I have

$LimitTo4 = True;
res1=A0[m^2, A0ToB0 -> True]

-> m^2 + m^2 B0[0, m^2, m^2]

$LimitTo4 = False;
res2=A0[m^2, A0ToB0 -> True]

-> -((2 m^2 B0[0, m^2, m^2])/(2 - D))

The same can be also achieved with PaVeReduce by using the same option:

$LimitTo4 = True;
A0[m^2] // PaVeReduce[#, A0ToB0 -> True] &
PaVe[0, {}, {m^2}] // PaVeReduce // PaVeReduce[#, A0ToB0 -> True] &

$LimitTo4 = False;
A0[m^2] // PaVeReduce[#, A0ToB0 -> True] &
PaVe[0, {}, {m^2}] // PaVeReduce // PaVeReduce[#, A0ToB0 -> True] &

Both res1 and res2 are correct, as can be seen by comparing
the explicit analytic results:

PaXEvaluate[res1] - PaXEvaluate[res2]

-> 0

The only way to obtain m^2*B0[0, m^2, m^2] that I currently see would
be take the D->4 limit via

res2/.D->4

which is however not correct, since B0[0, m^2, m^2] is UV divergent and
thus there is a finite contribution from multiplying the 1/Epsilon pole
with the 1/(2-D) prefactor.

So a real example would be very helpful to understand what is the
problem that you are experiencing.

Cheers,
Vladyslav

Am 01.06.2016 um 11:24 schrieb Steffen Schwertfeger:
> Dear all,
>
> using the latest dev version of FeynCalc I can not reproduce some of my
> earlier results. I also noticed that A0[m^2] reduces to
>
> m^2*B0[0, m^2, m^2]
>
> while the latest stable release yields
>
> m^2 + m^2*B0[0, m^2, m^2].
>
> Now I am not 100% certain that this is an error or a question of
> definition.
>
> Kind regards,
> Steffen Schwertfeger
>



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