General relativistic resistive magnetohydrodynamics with Whisky Seminar

We present a new numerical implementation of the general-relativistic resistive magnetohydrodynamics (GR-RMHD) equations within the Whisky code. The numerical method adopted exploits the properties of Implicit-Explicit Runge-Kutta (RKIMEX) numerical schemes to treat the stiff terms of the equations. Using tests in 1D, 2D and 3D we show that our method is robust and recovers the ideal-MHD limit in regimes of very high conductivity. Moreover, the results illustrate that the code is capable of describing physical setups in all ranges of conductivities. In addition to tests in flat spacetime, we report simulations of magnetized nonrotating stars both in the Cowling approximation and in dynamical spacetimes. The case of the collapsing star has also been extensively studied because it provides a very good testbed for numerical codes with dynamical electromagnetic fields in strong gravity and because of its astrophysical relevance. We show that our results for a star collapsing to a black hole are in good agreement with the perturbative studies of the dynamics of electromagnetic fields in a Schwarzschild background. Finally, going beyond the simplified electrovacuum numerical modeling of the exterior of a magnetized neutron star within the WhiskyRMHD code is going to be discussed in the context of matched resistive MHD and force-free electrodynamics.