**Next message:**Vladyslav Shtabovenko: "Re: H->gluon,gluon and wrong result?"**Previous message:**Xiu-Lei Ren: "Question about TID in FC9.2.0"**In reply to:**Xiu-Lei Ren: "Question about TID in FC9.2.0"**Next in thread:**Vladyslav Shtabovenko: "Re: Question about TID in FC9.2.0"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]**Mail actions:**[ respond to this message ] [ mail a new topic ]

Hi,

in FeynCalc 9.2 I introduced strict checking on the dimensions of the

input in TID. This is done to avoid issues like this one:

<https://feyncalc.org/forum/1115.html>

where people don't pay attention to their input expressions and then

complain about seemingly inconsistent results. So unless people have

activated the BMHV regularization scheme, TID will complain about

expressions that contain both 4-dim and D-dim objects, as such terms are

not allowed in the naive/conventional dimensional regularization, where

*everything* is taken to be D-dimensional and the limit D->4 is taken

only at the very end of the calculation.

In your case everything is almost correct, up to the spinors.

SpinorUBar, SpinorU etc. always depend on 4-dim momenta, so putting

something like Momentum[p1, D] there doesn't really make sense. I guess,

I should better block this kind of input, so thanks for this example.

Anyhow, in FC 9.2 there are now also FCE input expressions for spinors

that depend on D-dim momenta, namely SpinorUBarD, SpinorUD etc., c.f.

<https://github.com/FeynCalc/feyncalc/blob/master/FeynCalc/Changelog.md#version-920-november-2016>

So, the correct expression reads:

TID[(SpinorUBarD[p3, mN].GAD[\[Mu]].SpinorUD[p1, mN]) (SpinorUBarD[p4,

mN].GAD[\[Nu]].GAD[\[Omega]].GAD[\[Rho]].SpinorUD[p2,

mN]) ((2 FVD[l, \[Mu]] + FVD[q, \[Mu]]) FVD[

l, \[Nu]] (FVD[p4, \[Omega]] -

FVD[l, \[Omega]]) (FVD[l, \[Rho]] +

FVD[q, \[Rho]])) FeynAmpDenominator[

PropagatorDenominator[Momentum[l, D], m\[Pi]],

PropagatorDenominator[Momentum[l + q, D], m\[Pi]],

PropagatorDenominator[Momentum[p4 - l, D], mN]], l,

UsePaVeBasis -> True, PaVeAutoReduce -> False]

BTW, there is no need to use FeynAmpDenominator when writing down input

integrals, FAD is fully sufficient and makes things shorter and faster

to write:

TID[(SpinorUBarD[p3, mN].GAD[\[Mu]].SpinorUD[p1, mN]) (SpinorUBarD[p4,

mN].GAD[\[Nu]].GAD[\[Omega]].GAD[\[Rho]].SpinorUD[p2,

mN]) ((2 FVD[l, \[Mu]] + FVD[q, \[Mu]]) FVD[

l, \[Nu]] (FVD[p4, \[Omega]] -

FVD[l, \[Omega]]) (FVD[l, \[Rho]] + FVD[q, \[Rho]])) FAD[{l,

m\[Pi]}, {l + q, m\[Pi]}, {-l + p4, mN}], l, UsePaVeBasis -> True,

PaVeAutoReduce -> False]

Cheers,

Vladyslav

Am 17.12.2016 um 11:19 schrieb Xiu-Lei Ren:

*> Dear Vladyslav,
*

*>
*

*> Recently, I use the TID to calcualte a triangle diagram,
*

*> where the dirac spinors are explicitly involved.
*

*>
*

*> TID[ (SpinorUBar[Momentum[p3, D], mN].GAD[\[Mu]].SpinorU[
*

*> Momentum[p1, D], mN]) (SpinorUBar[Momentum[p4, D],
*

*> mN].GAD[\[Nu]].GAD[\[Omega]].GAD[\[Rho]].SpinorU[
*

*> Momentum[p2, D], mN]) ((2 FVD[l, \[Mu]] + FVD[q, \[Mu]]) FVD[
*

*> l, \[Nu]] (FVD[p4, \[Omega]] -
*

*> FVD[l, \[Omega]]) (FVD[l, \[Rho]] +
*

*> FVD[q, \[Rho]])) FeynAmpDenominator[
*

*> PropagatorDenominator[Momentum[l, D], m\[Pi]],
*

*> PropagatorDenominator[Momentum[l + q, D], m\[Pi]],
*

*> PropagatorDenominator[Momentum[p4 - l, D], mN]], l,
*

*> UsePaVeBasis -> True, PaVeAutoReduce -> False]
*

*>
*

*> Unfortunately, TID not works with
*

*>
*

*> TID::failmsg: Error! TID has encountered a fatal problem and must abort the computation. The problem reads: Your input contains a mixture of 4- and D-dimensional quantities. This i\[Ellipsis] on, unless you are using the Breitenlohner-Maison-t'Hooft-Veltman scheme. >>
*

*>
*

*> When I use FC9.0.1 to do such calculation, there is no problem.
*

*>
*

*> Could you kindly let me what should I do in FC9.2.0?
*

*>
*

*> Thanks in advance!
*

*> Xiu-Lei Ren
*

*>
*

**Next message:**Vladyslav Shtabovenko: "Re: H->gluon,gluon and wrong result?"**Previous message:**Xiu-Lei Ren: "Question about TID in FC9.2.0"**In reply to:**Xiu-Lei Ren: "Question about TID in FC9.2.0"**Next in thread:**Vladyslav Shtabovenko: "Re: Question about TID in FC9.2.0"**Messages sorted by:**[ date ] [ thread ] [ subject ] [ author ]**Mail actions:**[ respond to this message ] [ mail a new topic ]

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