[Users] Add a lapse condition

[Miguel Zilhão]

hi Erik,

you can also try with the LeanBSSNMoL thorn, which is not Kranc-generated. adding another gauge 
condition should be fairly simple; i can point you exactly to what you'd need to change in the code 
if you need.

cheers,
Miguel

On 24/10/19 16:21, Peter Diener wrote:
> 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
>>
>>
>>
> 
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