[Users] Oscillations in total angular momentum from QuasiLocalMeasures

Miguel Zilhão mzilhao at ua.pt
Mon Apr 1 09:33:12 CDT 2024


hi Sudipta and Erik,

just to mention that i've also seen similar behaviour in the ADM angular 
momentum reported by QuasiLocalMeasures in simulations with boson stars.

i don't have more detailed information at hand to provide (though i 
could find it if necessary), but i do recall that for simulation that 
i've done in the past with rotating boson stars, the ADM angular 
momentum reported oscillated widely. in same cases of the order of 100% 
of the expected value.

since this output was not crucial for my purposes at the time, and since 
all other diagnostic quantities that i looked at (including the ADM 
mass) looked totally fine, i never investigated this further.

but given what Sudipta reports, it could be worth to open an issue, and 
(once i have time to collect my data) i'd be happy to add any 
information i may have there.

cheers,
Miguel


On 01/04/2024 13:25, Sudipta Hensh wrote:
> Hi Erik,
> 
> Sorry for the delayed reply, I was checking possible correlations with 
> the oscillation frequency and other parameters. However, I have not 
> found anything like that. If we increase the spatial resolution then the 
> oscillation amplitude changes slightly while the frequency seems to be 
> almost unchanged, so this information may not be useful.
> 
> I am looking forward to hearing from you,
> Sudipta
> 
> Erik Schnetter wrote:
> 
> 
>> Sudipta
>>
>> Does the oscillation frequency coincide with anything in your
>> discretization? Is it related to your time step size or to the size of
>> a grid cell?
>>
>> What happens if you change the spatial resolution?
>>
>> -erik
>>
>>
>> On Thu, Mar 21, 2024 at 8:28 AM Sudipta Hensh <hensh at astro-osaka.jp> 
>> wrote:
>>
>>>
>>> Hi Erik,
>>>
>>> Sorry for the delay, I have written below the answers.
>>>
>>> 1. What is the size of the simulation domain?
>>>
>>> Simulation domain along x and y direction is [-1000,1000] and along z 
>>> direction is [0,1000].
>>>
>>> 2. At which radius do you evaluate the angular momentum?
>>>
>>> There are two extraction radii, 200 and 300. The plot that I sent was 
>>> for 300.
>>>
>>> 3. What is the spatial resolution there?
>>>
>>> Spatial resolution is 5.
>>>
>>> 4. What is the time resolution there?
>>>
>>> The time resolution is 0.75.
>>>
>>> 5. Is there any matter nearby?
>>>
>>> There is no matter during the inspiral.
>>>
>>> 6. What happens if you change the evaluation radius? What if you make it
>>> smaller or larger?
>>>
>>> For smaller radius the amplitude of oscillations is comparatively 
>>> smaller.
>>>
>>> 7. How close is this to the outer boundary?
>>>
>>> The extraction radius is far from the outer boundary.
>>>
>>> 8. Do you have a visualisation of the geometry (e.g. the imaginary part
>>> of the Weyl scalar Psi_2)?
>>>
>>> I am afraid that I do not have Psi_2 in the output. If necessary then 
>>> I can output it.
>>>
>>> 9. In which direction does the angular momentum point?
>>> Does this change over time?
>>>
>>> The plot I sent was for the angular momentum along z direction.
>>>
>>> 10. What is the magnitude of the angular momentum? How does this compare
>>> to the mass?
>>>
>>> The initial magnitude of the angular momentum is 7.3 and total 
>>> gravitational mass of the system is 2.75 M_Sun.
>>>
>>> I am leaving below some information from the parameter file that 
>>> maybe relevant.
>>>
>>> CoordBase::xmin                = -1000
>>> CoordBase::xmax                =  1000
>>> CoordBase::ymin                = -1000
>>> CoordBase::ymax                =  1000
>>> CoordBase::zmin                =  0
>>> CoordBase::zmax                =  1000
>>> CoordBase::spacing                      = "numcells"
>>> CoordBase::ncells_x                    = 200
>>> CoordBase::ncells_y                    = 200
>>> CoordBase::ncells_z                    = 100
>>>
>>> Carpet::max_refinement_levels          = 8
>>> Carpet::time_refinement_factors        = 
>>> "[1,1,2,4,8,16,32,64,128,256,512]"
>>>
>>>
>>> CarpetRegrid2::num_centres              = 3
>>> CarpetRegrid2::regrid_every            = 128
>>> CarpetRegrid2::snap_to_coarse          = "yes"
>>> CarpetRegrid2::freeze_unaligned_levels          = "yes"
>>> CarpetRegrid2::freeze_unaligned_parent_levels  = "yes"
>>>
>>> # ----------- Region 1 --------------------
>>> CarpetRegrid2::active_1                = "yes"
>>> CarpetRegrid2::num_levels_1            = 7
>>> CarpetRegrid2::position_x_1            = 15.2365094091
>>> CarpetRegrid2::position_y_1            = 0.0
>>> CarpetRegrid2::radius_1[1]              = 300.0
>>> CarpetRegrid2::radius_1[2]              = 160.0
>>> CarpetRegrid2::radius_1[3]              = 80.0
>>> CarpetRegrid2::radius_1[4]              = 40.0
>>> CarpetRegrid2::radius_1[5]              = 20.0
>>> CarpetRegrid2::radius_1[6]              = 10.0
>>>
>>> # ----------- Region 2 --------------------
>>> CarpetRegrid2::active_2                = "yes"
>>> CarpetRegrid2::num_levels_2            = 7
>>> CarpetRegrid2::position_x_2            = -15.2365094091
>>> CarpetRegrid2::position_y_2            = -0.0
>>> CarpetRegrid2::radius_2[1]              = 300.0
>>> CarpetRegrid2::radius_2[2]              = 160.0
>>> CarpetRegrid2::radius_2[3]              = 80.0
>>> CarpetRegrid2::radius_2[4]              = 40.0
>>> CarpetRegrid2::radius_2[5]              = 20.0
>>> CarpetRegrid2::radius_2[6]              = 10.0
>>>
>>> # ----------- Region 3 --------------------
>>> CarpetRegrid2::active_3        = "yes"
>>> CarpetRegrid2::num_levels_3            = 3
>>> CarpetRegrid2::position_x_3            = 0
>>> CarpetRegrid2::radius_3[1]              = 320.0
>>> CarpetRegrid2::radius_3[2]              = 160.0
>>> CarpetRegrid2::radius_3[3]              = 80.0
>>> CarpetRegrid2::radius_3[4]              = 40.0
>>> CarpetRegrid2::radius_x_3[5]            = 30.0
>>> CarpetRegrid2::radius_y_3[5]            = 30.0
>>> CarpetRegrid2::radius_z_3[5]            = 25.0
>>> CarpetRegrid2::radius_3[6]              = 20.0
>>> CarpetRegrid2::radius_3[7]              = 5.0
>>> # -----------------------------------------
>>>
>>> Thanks for your time. I would look forward to hearing from you.
>>>
>>> Thanks,
>>> Sudipta
>>>
>>> Sudipta Hensh
>>> JSPS Postdoctoral Researcher
>>> Pronouns: He/Him
>>> Graduate School of Science
>>> Osaka University
>>> 1-1 Machikaneyama-cho, Toyonaka
>>> Osaka 560-0043, Japan
>>>
>>> Erik Schnetter wrote:
>>>
>>>
>>> Sudipta
>>>
>>> What is the size of the simulation domain?
>>> At which radius do you evaluate the angular momentum?
>>> What is the spatial resolution there?
>>> What is the time resolution there?
>>> Is there any matter nearby?
>>> What happens if you change the evaluation radius? What if you make it
>>> smaller or larger?
>>> How close is this to the outer boundary?
>>> Do you have a visualisation of the geometry (e.g. the imaginary part
>>> of the Weyl scalar Psi_2)?
>>> In which direction does the angular momentum point?
>>> Does this change over time?
>>> What is the magnitude of the angular momentum? How does this compare
>>> to the mass?
>>>
>>> -erik
>>>
>>>
>>> On Tue, Mar 19, 2024 at 9:35 AM Sudipta Hensh <hensh at astro-osaka.jp> 
>>> wrote:
>>>
>>>
>>>>
>>>> Dear all,
>>>>
>>>> I hope this email finds you well.
>>>>
>>>> I am performing simulations of BNS mergers and utilizing the 
>>>> QuasiLocalMeasures thorn to plot the total angular momentum of the 
>>>> spacetime. However, I have noticed high-frequency oscillations in 
>>>> the plotted data, as shown in the attached plot. I was wondering if 
>>>> we should expect such oscillations. I would also like to know the 
>>>> reason behind such oscillations. I would appreciate if you kindly 
>>>> help me to understand this issue.
>>>>
>>>> I am looking forward to hearing from you. Many thanks in advance!
>>>>
>>>> Regards,
>>>> Sudipta Hensh
>>>> JSPS Postdoctoral Researcher
>>>> Pronouns: He/Him
>>>> Graduate School of Science
>>>> Osaka University
>>>> 1-1 Machikaneyama-cho, Toyonaka
>>>> Osaka 560-0043, Japan
>>>> _______________________________________________
>>>> Users mailing list
>>>> Users at einsteintoolkit.org
>>>>
>>>
>>> http://lists.einsteintoolkit.org/mailman/listinfo/users
>>>
>>>
>>>
>>> --
>>> Erik Schnetter <schnetter at gmail.com>
>>> http://www.perimeterinstitute.ca/personal/eschnetter/
>>>
>>>
>>
>>
>>
>> -- 
>> Erik Schnetter <schnetter at gmail.com>
>> http://www.perimeterinstitute.ca/personal/eschnetter/
>>
>>
>> <
>>
>> <
>>
> 
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