Hi Nick,
Your approach of modifiying TOVSolver::TOV_Rho_Central[0] in your
parameter file just results in an different equilibrium
solution.
However, the TOV-solver actually have built in parameters for doing
exactly what you want.
If you set
TOVSolve::Perturb[0] = "yes"
you can add a perturbation to the density before writing the initial
data to the grid.
You'll also need to set TOVSolver::Pert_Amplitude[0] to some nonzero
value in order for a nonzero perturbation to be added.
The initial data, written to the grid, will of course no longer satisfy
the constraint equations but for your purpose that should be okay.
Other ways of adding perturbations could also be to use different values
of TOVSolver::TOV_Gamma and/or TOVSolver::TOV_K for the initial data
thorn and for the evolution thorn.
Cheers,
Peter
On Friday 2020-10-16 18:11, Nick Olsen wrote:
Date: Fri, 16 Oct 2020 18:11:22
From: Nick Olsen <[email protected]>
To: [email protected]
Subject: [Users] TOV Solver and Equilibrium
Hello
I am a master's student working on general relativity and in my project we
have gotten to a point where we need to solve the Einstein equations. We are
not numerical relativity experts but we have started getting familiarized
with the Einstein Toolkit.
After playing with it for a while I have realized that I can’t even run a
very simple example where I get the TOV equilibrium parameter file from the
par folder of the ET installation and modify it to take it a little bit out
of equilibrium and see it numerically evolve back to a new equilibrium
situation (say for example changing the density profile). I have tried
modifying rho_central in the file tov_star.par however it seems that after
that modification the system does not evolve to a new equilibrium. I was
wondering if somebody here can point me in the right direction. Thank you so
much in advance.
Nicholas Olsen
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