<div dir="ltr">Hi Peter,<div><br></div><div>Thanks so much! I asked because I'd like to try running simulations with the modified shift condition described in this paper (second page): <a href="https://arxiv.org/abs/gr-qc/0511103">https://arxiv.org/abs/gr-qc/0511103</a></div><div><br></div><div>Some terms that feature in the usual gamma driver equations are dropped, and the lapse appears in the time derivative of beta. Would I have to make changes to the Kranc code in order to implement such a condition?</div><div><br></div><div>Best,</div><div><br></div><div>Gwyneth</div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Wed, Dec 28, 2016 at 10:57 AM, Peter Diener <span dir="ltr"><<a href="mailto:diener@cct.lsu.edu" target="_blank">diener@cct.lsu.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi Gwyneth,<br>
<br>
The parameters to control the gamma driver shift condition is something<br>
that we would like to make more transparent. I have to go and look at<br>
the Kranc code, in order to figure out how things work.<br>
<br>
When ShiftBCoeff = 1 and ShiftAdvectionCoeff = 1 (both are the default<br>
values) we are evolving the gamma driver shift that is listed on the<br>
wiki you point to.<br>
<br>
ShiftGammaCoeff should be set to 0.75 (it's the 3/4 in the equation for<br>
the shift). It's unfortunate that 0.75 is not the default value for<br>
ShiftGammaCoeff, as this is the only value that is ever used (as far as<br>
I know). BetaDriver is the eta value in the eqaution for B.<br>
ShiftAlphaPower is a leftover parameter from before the moving puncture<br>
approach came into use and currently has no effect in the code.<br>
<br>
Let me know if you have any other questions.<br>
<br>
Cheers,<br>
<br>
Peter<br>
<br>
On Tuesday 2016-12-27 10:31, Gwyneth Allwright wrote:<br>
<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Date: Tue, 27 Dec 2016 10:31:55<br>
From: Gwyneth Allwright <<a href="mailto:allgwy001@myuct.ac.za" target="_blank">allgwy001@myuct.ac.za</a>><br>
To: <a href="mailto:users@einsteintoolkit.org" target="_blank">users@einsteintoolkit.org</a><br>
Subject: [Users] McLachlan Shift Condition<div><div class="h5"><br>
<br>
Hi All,<br>
<br>
I'm new to the Einstein Toolkit and would like to double check what the<br>
ML_BSSN parameters ShiftGammaCoeff, BetaDriver and ShiftAlphaPower refer to.<br>
I tried looking in the param.ccl file, but it still wasn't 100% clear to me.<br>
<br>
As far as I understand, the shift condition used by McLachlan is the gamma<br>
driver, given here: <a href="http://grwiki.physics.ncsu.edu/wiki/Shift_Conditions" rel="noreferrer" target="_blank">http://grwiki.physics.ncsu.edu<wbr>/wiki/Shift_Conditions</a>.<br>
What value of eta does ML_BSSN use?<br>
<br>
Thanks,<br>
<br>
Gwyneth<br>
<br>
<br>
</div></div></blockquote>
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