A conservation law formulation of nonlinear elasticity in general relativity

Monday, October 14, 2013, 10am US central time

The Einstein Toolkit BigBlueButton meeting was be used for audio and slides. The recordings are available in Theora or MP4 format.


After months of work, I am pleased to release my rewrite of the Illinois numerical relativity group's staggered A-field GRMHD thorn to the ET community. The new thorn is called IllinoisGRMHD, and yields results identical (within roundoff error) to the original GRMHD code of the Illinois group with AMR & unigrids, with bitant symmetry & without, and with single or multiple MPI processes. We used precisely these GRMHD algorithms to produce our latest GRMHD-based papers. IllinoisGRMHD is written entirely in C, except for some C++ file I/O for debugging purposes, and all loops are OpenMP-compatible. The coding standard is C99. I would like to thank Frank and the CCT folks, who have graciously agreed to host IllinoisGRMHD on the ET SVN server, as the thorn awaits maintainers' approval for incorporation into the official ET. Download IllinoisGRMHD via the following command:

svn co https://svn.einsteintoolkit.org/cactus/EinsteinEvolve/IllinoisGRMHD/trunk/
Browse IllinoisGRMHD source code in your web browser.


Roughly a decade of work has gone into the original code, and nearly all of the credit for debugging that battle-hardened code goes to Stu Shapiro and other former & current members of his group, to whom I give my great thanks and send the following message: Despite weeks entirely devoted to debugging this rewritten code, I found no major bugs in the original code.


The IllinoisGRMHD thorn is hereby released under the GNU GPL v2 or higher, to maximize compatibility with the ET thorns.

Presenter: Zachariah Etienne

Zachariah Etienne

JSI fellow at U. Maryland & NASA Goddard

Numerical Relativity Group Research interests: My research interests span all of computational astrophysics. Much of my past work has focused on simulating the mergers of compact binary systems, including BHNS, BHBH, WDNS, and NSNS. My current work focuses on BHBH mergers, as well as studying MHD effects in BHNS mergers.