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?
<https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=icon> Virus-free. www.avast.com <https://www.avast.com/sig-email?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=webmail&utm_term=link> <#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> On Mon, Nov 6, 2017 at 9:11 PM, Ian Hinder <ian.hin...@aei.mpg.de> wrote: > > On 5 Nov 2017, at 09:28, Nisa Amir <nisaa...@math.qau.edu.pk> wrote: > > > Actually, when in the einsteinexact thorn there is a mathematica package > named EinsteinExact. The documentation said that if you want to add some > new space time add the space time in that mathematica package. I want to > add non kerr which is in polar coordinates to that package, so that it > generates a new thorn but I dont know how to do that. > > Kindly guide me. > > Hi, > > Yes, you can add a new spacetime to the Metrics package (in > Cactus/arrangements/EinsteinExact/m/Metrics/metrics). See the examples in > there. For example, Schwarzschild.m: > > (* ::Package:: *) > > { > "Name" -> "Schwarzschild", > "Description" -> "Schwarzschild spacetime", > "Dimensions" -> 4, > "Coordinates" -> {t, r, \[Theta], \[Phi]}, > "Parameters" -> {M}, > "Metric" -> {{-1 + 2 M / r, 0, 0, 0}, > {0, 1/(1 - 2 M / r), 0, 0}, > {0, 0, r^2, 0}, > {0, 0, 0, r^2 Sin[\[Theta]]^2}}, > "SignDet" -> -1 > } > > The EinsteinExact package then uses this information to generate an exact > solution thorn, which can be used for initial data in a numerical > relativity evolution. However, it only supports metrics which are > explicitly given in Cartesian coordinates, so for example, the > Schwarzschild example won't work with it (the Metrics package is generic, > and is used also in other contexts, outside EinsteinExact). > > There is a check in arrangements/EinsteinExact/m/EinsteinExact.m that the > metric is in Cartesian coordinates. I suspect that the only reason for > this check is that it wouldn't know what Cactus gridfunctions to use for > anything else. > > Since you want to do the evolution in polar coordinates, I assume that you > are going to have some mapping between x, y and z, and r, th and ph? I > must admit I have never tried to do something like this. > > There are people on this list who have done evolutions in polar > coordinates; maybe one of them could give some advice about whether what > you are trying to do is feasible? Maybe you could give more details about > what you are trying to do? > > PS: *please* include users@einsteintoolkit.org in the CC when you reply. > If you reply just to me, then nobody else benefits from the discussion, and > nobody else has the opportunity to help you. > > -- > Ian Hinder > http://members.aei.mpg.de/ianhin > >
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