[Users] Oscillations in total angular momentum from QuasiLocalMeasures

Mon Apr 1 07:25:18 CDT 2024

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
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Erik Schnetter <schnetter at gmail.com>
http://www.perimeterinstitute.ca/personal/eschnetter/
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Erik Schnetter <schnetter at gmail.com>
http://www.perimeterinstitute.ca/personal/eschnetter/
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