<div dir="ltr"><p dir="ltr">Thanks Eloisa,</p>
<p dir="ltr">2015. 6. 26. 오후 8:50에 "Eloisa Bentivegna" <<a href="mailto:eloisa.bentivegna@ct.infn.it" target="_blank">eloisa.bentivegna@ct.infn.it</a>>님이 작성:<br>
><br>
> On 25/06/15 05:07, Hee Il Kim wrote:<br>
><br>
> >> Hi,<br>
> >><br>
> >> Recently, I found the multipole moment calculations in<br>
> >> QuasiLocalMeasures show large errors, e.g. 20% for the second mass<br>
> >> moment of my project.<br>
> ><br>
> > [...]<br>
> ><br>
> > I understand. But the issue is, even though I'm using sufficiently high<br>
> > resolution for my collapsing star study, the code calculates<br>
> > inaccurately the higher multipole moments for n >0, where n is the order<br>
> > of the Legendre polynomial. So it calculates the mass and the spin very<br>
> > accurately.<br>
><br>
> Dear Hee Il,<br>
><br>
> thanks for reporting the issue. May I ask: how are you testing the code?<br>
> Which quantities are you comparing to the output of QLM, and how did you<br>
> obtain them (a formula, another code, etc.)?</p><p dir="ltr">What I have checked is actually to see whether the QLM results satisfy the no-hair theorem of Kerr black holes, i.e., to see whether,</p><p>M_0 = M_bh, M_2 = -(J_bh)^2/M_bh, ...</p><p>J_1= J_bh, J_3 = -(J_bh)^3/(M_bh)^2, ... , when the bh formed in the simulation becomes stationary.</p><p>E.g.,</p><p dir="ltr"><span style="font-size:14px">> plot "quasilocalmeasures::qlm_</span><span style="font-size:14px">multipole_moments..asc" u 9:(-$23*$23/$13)</span></p><div style="font-size:14px">> replot "quasilocalmeasures::qlm_multipole_moments..asc" u 9:15</div><div><br></div><div>where $23=M_bh, $13=J_bh, and the 15th column of the data represents the 2nd mass multipole moment of the bh.</div><div><br></div><p dir="ltr">
> I see that you mention a collapsing star: what multipoles are you<br>
> calculating in that case? QLM only computes the geometric multipoles of<br>
> 2D surfaces (and not, for instance, of the matter density). Does an<br>
> apparent horizon form in your simulation, and in that case, is this what<br>
> you are calculating the multipoles of?</p><p>Sorry for the confusion. The multipole, here, means the mutipole moment of the black hole found by the horizon finder (AHFinderDirect), not the multipole moment of matter.</p><p>Cheers,</p><p>Hee Il </p><p dir="ltr"><br>
</p>
</div>