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@ciencias.unam.mx To: users@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