Hi,
my name is Antoni Ramos Buades, I am PhD student at 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 modes 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 ), indeed I cannot even attach some snapshots because then the message exceeds the limit of 1000KB and the message gets stuck on the moderator approval procedure of the mailing list ( two days have already passed ...). So I have sent a minimal version without the snapshots. In the movie or the snapshots one observes 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 somebody has ever seen this thing happening before and if somebody knows how one could solve this problem, if adding some additional parameters to the parameter file (attached to this email) can prevent this from happening, 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 it does. 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.
