[Users] Eccentricity in BNS evolution with Lorene

[Bing-Jyun Tsao]

Dear Einstein Toolkit community,

I am Bing-Jyun (Johnny) Tsao, a graduate student at University of Texas at
Austin. I am currently working on a project comparing our local version of
BNS initial data (M. Clark, P. Laguna, 2016 Physical Review D 94 064058)
with Lorene.

When using Lorene, I found that the trajectory of the stars is showing
eccentricity (as shown in the plot below), and this occurred when I ran
Lorene with equal-mass BNS with ADM mass = 1.4 Msun, and with the
publicly available Lorene data on their website "G2_I14vs14_D4R33_45km",
both of which have an initial separation of 45 km. I use
VolumeIntegral_GRMHD to track the stars, and GRHydro + ML_BSSN to evolve.
Additionally, I also found that the ADM angular momentum from Lorene is
about 20% smaller than that from our code which uses post-Newtonian
calculations.

My question is:
>From my understanding, Lorene gives quasi-circular initial data. Thus,
is it abnormal to see eccentricity, or is it a physical artifact, perhaps
from tidal deformation, that always shows up when the stars are very close
to each other?

Here I attached my parfile and the trajectory for a run using the Lorene
publicly available data "G2_I14vs14_D4R33_45km".

Thanks in advance.

Best,
Johnny Tsao
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