[Users] weird behavior with some ET simulations

[Antoni Ramos Buades]

Hi,

my name is Antoni Ramos Buades, I am PhD student in the University of the
Balearic Islands working with Sascha Husa. We have been using ET with the
Llama thorn to produce waveforms. We have observed in some simulations
strange behaviors in the waveforms. For example, I have attached a plot of
the amplitude of the psi4 of a non-spinning q1 simulation, for different
higher order modes, where you can see that the 22, 32 and 44 show weird
spikes. We have rerun this simulation outputting 2D data in the x-y plane.
We have plotted the Hamiltonian constraint and made a movie (I cannot
attach the movie because its size is 42Mb ) but I can attach some snapshots
where you can observe that there seems to be an outburst of noise when the
boxes are aligned, and this continues happening in the simulation each time
the boxes are aligned with each other. Geraint Pratten is also
investigating this issue  adding some new parameters in the parameter file
(attached to the email) for the carpet mesh refinement like
freeze_unaligned_parent_levels, freeze_unaligned_levels, ... and running
some tests.

We would like to ask you if somebidy has ever seen this thing happening
before and if somebody knows how one could solve this problem, because with
the same Carpet settings we have observed that for some configurations
(mass ratio and spins) this does not happen, but for others, like the one
presented in this email we do. I have additional quantities as a 2D output
like the curvature, metric, horizon, ... in case you think they could be
used to check something.

Thanks and best regards,
Toni.
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