[Users] Accuracy issue of multipole moment calculations in QuasiLocalMeasures

[Eloisa Bentivegna]

On 25/06/15 05:07, Hee Il Kim wrote:

>>     Hi,
>>
>>     Recently, I found the multipole moment calculations in
>>     QuasiLocalMeasures show large errors, e.g. 20% for the second mass
>>     moment of my project. 
>
> [...]
>
> I understand. But the issue is, even though I'm using sufficiently high
> resolution for my collapsing star study, the code calculates
> inaccurately the higher multipole moments for n >0, where n is the order
> of the Legendre polynomial. So it calculates the mass and the spin very
> accurately.

Dear Hee Il,

thanks for reporting the issue. May I ask: how are you testing the code?
Which quantities are you comparing to the output of QLM, and how did you
obtain them (a formula, another code, etc.)?

I see that you mention a collapsing star: what multipoles are you
calculating in that case? QLM only computes the geometric multipoles of
2D surfaces (and not, for instance, of the matter density). Does an
apparent horizon form in your simulation, and in that case, is this what
you are calculating the multipoles of?

Best,
Eloisa