General relativistic magnetohydrodynamic simulations with BAM: Implementation and code comparison

Binary neutron star mergers are among the most energetic events in our Universe, with magnetic fields significantly impacting their dynamics, particularly after the merger. While numerical-relativity simulations that correctly describe the physics are essential to model their rich phenomenology, the inclusion of magnetic fields is crucial for realistic simulations. For this reason, we have extended the bam code to enable general relativistic magnetohydrodynamic (GRMHD) simulations employing a hyperbolic “divergence cleaning” scheme. We present a large set of standard GRMHD tests and compare the bam code to other GRMHD codes, spritz, gram-x, and SACR_AKK⁢22, which employ different schemes for the evolution of the magnetic fields. Overall, we find that the bam code shows good performance in simple special-relativistic tests. In addition, we find good agreement and consistent results when comparing GRMHD simulation results between bam and SACRA_KK⁢22.