[Users] TOVSolver interpolation algorithm

[Gabriele Bozzola]

Hi CJ,

Yes, that's correct. The solution of the TOV equation is in Schwarzschild
coordinates, but it is in isotropic coordinates when
mapped onto the 3D grid.

Best,
Gabriele

On Mon, Sep 23, 2024 at 9:20 AM CJ Osakwe <cuosakwe at ucalgary.ca> wrote:

> Hello Gabriele,
>
> Thanks for the response. Does this mean that the final (3D) output of the
> thorn is also in isotropic coordinates?
>
> Cheers,
> CJ
> ------------------------------
> *From:* Gabriele Bozzola <bozzola.gabriele at gmail.com>
> *Sent:* Saturday, September 14, 2024 5:33 PM
> *To:* CJ Osakwe <cuosakwe at ucalgary.ca>
> *Cc:* users at einsteintoolkit.org <users at einsteintoolkit.org>
> *Subject:* Re: [Users] TOVSolver interpolation algorithm
>
> [△EXTERNAL]
>
> Hi CJ Osakwe,
>
> 1D and 3D solutions look different because different coordinate systems
> are being used,
> so the meaning of "radius" changes. More specifically, Schwarzschild
> coordinates in 1D, but
> 3D interpolation is performed with isotropic coordinates, which tend to be
> better behaved
> for numerical relativity simulations.
>
> You can find more information here:
>
> https://einsteintoolkit.org/thornguide/EinsteinInitialData/TOVSolver/documentation.html
>
> Best,
> Gabriele
>
>
>
>
> On Fri, Sep 13, 2024 at 10:31 AM CJ Osakwe <cuosakwe at ucalgary.ca> wrote:
>
> Hello,
>
> Thank you for your response to my previous inquiry. I am now trying to
> model a hybrid star in the Einstein Toolkit, and I have some questions
> about the algorithm in the TOVSolver thorn that takes the 1D solution to
> the TOV equations and interpolates it to the 3D grid.
>
> I was able to extract the 1D data and plot it, but when I do, the pressure
> v. radius and density v. radius relations noticeably change (they both
> decrease sooner and reach zero sooner in the 3D case than the 1D case). I
> am wondering why this happens, and if it should be expected.
>
> Cheers,
> CJ Osakwe
>
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