Re: Question about mfpetersson

Dear Ahmad,

It looks like a bug to me, but I will check with Karim and Henri who 
wrote this package.

One line looks suspicious to me:

   if (!gequal0(gel(ESF,1)) && !gequal0(gel(ESG,1)))
     return mfpeterssonnoncusp(FS, GS);

When changing && to ||, we obtain:

? mfpetersson(mfsymbol(mfDelta), 
mfsymbol(mflinear([mfDelta,mfEk(12)],[1,2])))
%1 = 1.0353620568043209223478168122251645992 E-6 - 1.4909815660416053635 
E-42*I
? mfpetersson(mfsymbol(mfDelta), 
mfsymbol(mflinear([mfDelta,mfEk(12)],[1,0])))
%2 = 1.0353620568043209223478168122251645932 E-6 + 0.E-44*I
? mfpetersson(mfsymbol(mfDelta), 
mfsymbol(mflinear([mfDelta,mfEk(12)],[0,1])))
%3 = 1.1364530545674266445 E-42 - 5.829401611591239015 E-43*I

But I may be misunderstanding what the code is supposed to do.

Best,
Aurel

On 17/03/2025 12:38, Ahmad Mostafa Ismail El-Guindy wrote:
> Hello,
>
> I am not sure what exactly am I doing wrong, but I am getting 
> unexpected behavior from mfpetersson which seems to violate linearity. 
> Since <Delta, E_{12}>=0 shouldn't the first line below give <Delta, 
> Delta>? Why is it returning 0 instead?
>
> (12:22) gp > mfpetersson(mfsymbol(mfDelta), 
> mfsymbol(mflinear([mfDelta,mfEk(12)],[1,2])))
> %43 = 0
> (12:25) gp > mfpetersson(mfsymbol(mfDelta), 
> mfsymbol(mflinear([mfDelta,mfEk(12)],[1,0])))
> %44 = 1.0353620568043209223478168122251645932 E-6 + 0.E-44*I
> (12:25) gp > mfpetersson(mfsymbol(mfDelta), 
> mfsymbol(mflinear([mfDelta,mfEk(12)],[0,1])))
> %45 = 0
>
> Thanks,
>
> Ahmad