# [Users] [Fwd: Kerr ID]

Bruno Coutinho Mundim bcmsma at astro.rit.edu
Wed Oct 6 19:29:42 CDT 2010

Hi Scott and Erik,

I was also looking into this issue now. The mapping from the PRD 54 1403
paper to the code documentation seems to go as in:

Paper                          Documentation
r                                 r_k
\bar{r}                              r

Also note that the Sigma definition in the documentation is not the
usual definition in Boyer-Lindquist coordinates.

I hope there is a reference for the documentation. Otherwise, the
non-usual notation there prevents us of a simple check.

Thanks,
Bruno.

Erik Schnetter wrote:
> Scott
>
> Do you have a pointer to literature that contains the correct
> equation? I'm looking at PRD 54 1403, which is the paper cited in the
> thorn; is that a good choice? Do you know how the variables in the
> paper are mapped to the variables in the code? The code documentation
> (the latex file doc/documentation.tex) seems consistent with the C
> code, but of course both could be wrong. Or is there an easy way to
> see why the factor Sigma is missing?
>
> I haven't used the Boyer-Lindquist Kerr initial data implemented in
> this thorn myself; I usually use Kerr-Schild coordinates form thorn
> Exact.
>
> -erik
>
> On Wed, Oct 6, 2010 at 11:18 AM, Scott Noble <scn at astro.rit.edu> wrote:
>> I see that this has not been patched yet.  Can someone please confirm the
>> fix and
>> patch the repo?
>>
>> thanks, scott n.
>>
>>
>> -------- Original Message --------
>> Subject: Kerr ID
>> Date: Mon, 07 Jun 2010 16:54:20 -0400
>> From: Scott Noble <scn at astro.rit.edu>
>> To: users at einsteintoolkit.org
>>
>>
>> Hello Users,
>>
>>
>> I believe I found a minor typo in
>>
>> EinsteinInitialData/IDAnalyticBH/src/Kerr.c
>>
>> of the ET.   Just a missing term in the denominator of the shift vector, so
>> it will not likely affect many users.   I have attached a patch.
>>
>> cheers,
>>
>> -- scott n.
>>
>>
>>
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>
>
>