[Users] Failed to calculate the magnitude of the horizon spin in precessing BBH system

[Erik Schnetter]

Yu Liu

QuasiLocalMeasures regular spin measurement assumes that the black hole
spin is roughly aligned with the z direction. A spin near the equatorial
plane does not work well. In this case you'll have to use the coordinate
spins (qlm_coordspinx, qlm_coordspiny, qlm_coordspinz); these are less
accurate for distorted black holes, but will still work very well under
these circumstances.

-erik


On Thu, Apr 22, 2021 at 10:43 PM 刘屿 <yuliumutian at gmail.com> wrote:

> Dear Cactus users,
>
> I am trying to simulate a precessing BBH system. When I analysed the mass
> of the black hole (qlm_mass), I found that the spin evolution (qlm_spin) is
> abnormal.
> [image: qlm_spin.png]
> The coordinate-base spin vector gives a value closer to what I set.
> [image: qlm_coordspin_norm.png]
> This is the initial parameters.
>
> ADMMass = 0.9898872694943947
> Mass Ratio = 1.0
> separation = 10.4
> spin1 = [-0.125  0.     0.   ]
> spin2 = [0.125 0.    0.   ]
> chi1 = [-0.5  0.   0. ]
> chi2 = [0.5 0.  0. ]
>
>
> I tried different methods for finding the killing vector field (i.e.
> QuasiLocalMeasures::killing_vector_method), but it didn't work.
>
> If the small black hole does not spin (spin2 = [0, 0, 0]), things will get
> better.
>
> The following is the difference between my parfile and GW150914.rpar
>
> $ diff GW150914.rpar BBH000.rpar
> 32,33c32,33
> < D = 10.0                    # Separation
> < q = 36.0/29.0               # Mass ratio: q = mp/mm >= 1
> ---
> > D = 10.4                    # Separation
> > q = 1              # Mass ratio: q = mp/mm >= 1
> 35,38c35,38
> < chip = [0, 0,  0.31]        # Dimensionsless spin of + BH (x0 > 0, more
> massive)
> < chim = [0, 0, -0.46]        # Dimensionsless spin of - BH (x0 < 0, less
> massive)
> < Pr = -0.00084541526517121;  # Radial linear momentum
> < Pphi = 0.09530152296974252; # Azimuthal linear momentum
> ---
> > chip = [-0.5, 0, 0]        # Dimensionsless spin of + BH (x0 > 0, more
> massive)
> > chim = [0.5, 0, 0]        # Dimensionsless spin of - BH (x0 < 0, less
> massive)
> > Pr = -0.000878483532190008
> > Pphi = 0.0927554222753844
> 261,265c261,265
> < CoordinatesSymmetry::reflection_z       = yes
> < CoordinatesSymmetry::stagger            = no
> < Coordinates::symmetry                   = "+z bitant"
> < Coordinates::additional_symmetry_size   = 1
> < Coordinates::verbose                    = no
> ---
> > ##CoordinatesSymmetry::reflection_z       = yes
> > ##CoordinatesSymmetry::stagger            = no
> > ##Coordinates::symmetry                   = "+z bitant"
> > ##Coordinates::additional_symmetry_size   = 1
> > ##Coordinates::verbose                    = no
> 552,553c552,553
> < SphericalSurface::maxntheta             = 66
> < SphericalSurface::maxnphi               = 124
> ---
> > SphericalSurface::maxntheta             = 161
> > SphericalSurface::maxnphi               = 320
> 559,560c559,560
> < SphericalSurface::ntheta            [2] = 41
> < SphericalSurface::nphi              [2] = 80
> ---
> > SphericalSurface::ntheta            [2] = 161
> > SphericalSurface::nphi              [2] = 320
> 565,566c565,566
> < SphericalSurface::ntheta            [3] = 41
> < SphericalSurface::nphi              [3] = 80
> ---
> > SphericalSurface::ntheta            [3] = 161
> > SphericalSurface::nphi              [3] = 320
> 571,572c571,572
> < SphericalSurface::ntheta            [4] = 41
> < SphericalSurface::nphi              [4] = 80
> ---
> > SphericalSurface::ntheta            [4] = 161
> > SphericalSurface::nphi              [4] = 320
> 633,634c633,638
> < IOScalar::outScalar_reductions          = "minimum maximum average"
> < IOScalar::outScalar_vars                =
> "SystemStatistics::process_memory_mb"
> ---
> > IOScalar::outScalar_reductions          = "minimum maximum average norm1
> norm2"
> > IOScalar::outScalar_vars                = "
> >   SystemStatistics::process_memory_mb
> >   ML_ADMConstraints::ML_Ham
> >   ML_ADMConstraints::ML_mom
> > "
> 670c674
> < IOHDF5::out2D_every                     = $out2d_every
> ---
> > IOHDF5::out2D_every                     = 0
>
>
> Thank You
> Best Regards
>
> ---------------------------
>
> Yu Liu
> PhD Student
> Department of Astronomy
> Huazhong University of Science and Technology
> _______________________________________________
> Users mailing list
> Users at einsteintoolkit.org
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>


-- 
Erik Schnetter <schnetter at cct.lsu.edu>
http://www.perimeterinstitute.ca/personal/eschnetter/
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