Nicholas Instead of modifying an existing (and complicated, because it has many features) thorn, I would recommend first writing a simple thorn by yourself. I'd be happy to meet via Zoom and chat.
-erik On Fri, Jul 23, 2021 at 8:24 AM Roland Haas <[email protected]> wrote: > > Hello Nicholas, > > my guess would be that the assumption that rho>0 is showing in lots of > places in GRhydro thus not likely to be easily removed. > > Just to be sure: "rho" in GRHyro is the rest-mass density, basically > the number density multiplied by the rest mass of the particles. For > photons this seems to be an hard quantitiy to define. > > The energy density ("tt-component of the stress energy tensor") on the > other hand is not actually evolved by GRhydro and is instead either > provided part of the stress energy tensor in the TmunuBase::eTtt > variable. > > GRHydro (and the Valencia formulation of hydrotdynamics that it uses) > does involve (almost) this component of Tmunu in its "energy density" > variable "E" but usually that one is not directly evolved and instead > "tau" the difference between total energy "E" and relativistic > rest-mass energy "D" is evolved. > > Please see: > > https://link.springer.com/article/10.12942/lrr-2008-7#Sec2.1.3 > > and > > https://www.einsteintoolkit.org/thornguide/EinsteinEvolve/GRHydro/documentation.html#x1-80003 > > for the definitions. > > Since you are at Waterloo you should also be able to reach out to > people at Perimeter institute (Luis Lehner, Erik Schnetter come to > mind) who are experts on fluid dynamics and NR. > > Yours, > Roland > > > Hello there > > > > I have been learning how to use and working with the Einstein Toolkit for a > > few months now and I have gotten to a point where I wanted to implement a > > photon gas with (locally) negative rho as part of my research, following a > > paper written by one of my supervisor's PhD students. While looking into it > > I found that GRHydro automatically discards negative values of rho and > > replaces them with rho_abs_min, and I can't set rho_ans_min to a negative > > value because they are ignored according to the documentation. > > I was wondering if there is a way to set rho_abs_min to be negative without > > it being ignored, or a way to circumvent the check for negative values of > > rho somehow to allow for negative values. I have some experience with > > rewriting thorns for my own purposes but GRHydro isn't as simple as the > > thorns I've been changing. > > > > Thanks, > > Nicholas Olsen, University of Waterloo > > > > -- > My email is as private as my paper mail. I therefore support encrypting > and signing email messages. Get my PGP key from http://pgp.mit.edu . > _______________________________________________ > Users mailing list > [email protected] > http://lists.einsteintoolkit.org/mailman/listinfo/users -- Erik Schnetter <[email protected]> http://www.perimeterinstitute.ca/personal/eschnetter/ _______________________________________________ Users mailing list [email protected] http://lists.einsteintoolkit.org/mailman/listinfo/users
