[Users] Add a lapse condition

[Peter Diener]

Hi Erik,

McLachlan is a thorn generated from a tool named Kranc from 
high level tensorial expressions in Mathematica. So if you have
access to Mathematica you can add additional lapse conditions in the
mathematica source file located in:

arrangements/McLachlan/m/McLachlan_BSSN.m

and then regenerate the McLachlan thorn using

make McLachlan_BSSN.out

in the arrangements/McLachlan/m directory.

I admit the section on gauge conditions is rather messy as the selection 
of particular gauges are done based on conditionals on thorn parameters, 
but hopefully you can figure this out. Otherwise let me know and I'll be 
happy to help.

Cheers,

   Peter

On Thursday 2019-10-24 00:14, Erik Rodrígo Jiménez Vázquez wrote:

>Date: Thu, 24 Oct 2019 00:14:05
>From: Erik Rodrígo Jiménez Vázquez <erjive at ciencias.unam.mx>
>To: users at einsteintoolkit.org
>Subject: [Users] Add a lapse condition
>
>Dear all
>
>Is there a way to add different gauge conditions for the lapse? I'm trying
>to add a gauge shock avoid lapse for the Bona-Masso family of slicing
>conditions
>
>dot alpha = -alpha^2 f(alpha) K
>
>with f(alpha)=1+constant/alpha^2
>
>I don't know if I should add a thorn that complements the McLachlan thorn,
>or what is the correct procedure to implement the gauge condition?
>Furthermore, this kind of gauge condition allows to the lapse become
>negative which I know is a serious drawback when the lapse collapses to
>zero, however I want to do some numerical experiments with this kind of
>lapse.
>
>Any help is very welcome. Thanks
>Erik
>
>
>