[Users] evolving a BH hole with Kerr-Schild ID in ET

[Erik Schnetter]

Roland

This is almost possible. For puncture data, one typically evolves
lapse, shift, and a quantity B (the time derivative of the shift). For
Kerr-Schild data, one also needs to evolve A, the time derivative of
the lapse. Otherwise, Kerr-Schild data are not stationary. (One could
instead add an offset alpha_0 to the evolution equations for K, but
that is quite non-standard and not implemented in McLachlan.)

Additionally, I find it convenient to smooth all quantities near the
singularity, and to choose to advect both lapse and shift. I don't
know whether the latter is necessary in theory, but I am always using
it.

I can send a sample parameter file if that helps.

-erik


On Thu, Apr 25, 2019 at 10:38 AM Haas, Roland <rhaas at illinois.edu> wrote:
>
> Hello all,
>
> I am wondering if it is possible to take initial data for a single
> (maybe spinning) black whole in Kerr-Schild coordinates as provided by
> Exact or EinsteinExact (metric, curvature, lapse, shift, time
> derivatives of lapse and shift) and chose parameters for the "usual"
> 1+log and Gamma driver gauge evolution conditions so that this data is
> a stationary solution of the evolution equations?
>
> Yours,
> Roland
>
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Erik Schnetter <schnetter at gmail.com>
http://www.perimeterinstitute.ca/personal/eschnetter/