[Users] About the thorn Einstein exact

[Ian Hinder]

On 7 Nov 2017, at 14:04, Nisa Amir <nisaamir at math.qau.edu.pk> wrote:

> Yes, the mathematica package is given but it accepts the metric only in cartesian coordinates. I want to add the spacetime non kerr which is in polar coordinates to the mathematica package in Einstein Exact thorn. What transformations should I made?

Hi,

You can apply the usual basis transformations in Mathematica to generate the metric in a quasi-Cartesian basis and coordinates.  This will then allow you to construct the spacetime numerically in these coordinates, and the thorns in the toolkit which expect quasi-Cartesian coordinates will just work, for example the horizon finder.  You would then evolve in 3+1 dimensions.  I have done this for Kerr in Boyer-Lindquist coordinates using the xAct tensor manipulation package.  This is not straightforward, and it's not something that I would take on lightly if you don't have much experience with EinsteinExact or xAct.

However, you have said that you want to store the gridfunctions in polar coordinates, and do the evolution in polar coordinates.  I have no experience with this, and many of the thorns in the toolkit which expect quasi-Cartesian coordinates will just not work (e.g. the horizon finder).  That is why I asked you what you are trying to do.  Please can you answer that, before we go into a lot of detail about how to do it in one particular way, which may in the end not help you?

Thanks!

-- 
Ian Hinder
http://members.aei.mpg.de/ianhin

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.einsteintoolkit.org/pipermail/users/attachments/20171107/c2662133/attachment.html