GRoovy: a GRHayL-based code to solve the general relativistic hydrodynamics equations in dynamical spacetimes using singular curvilinear coordinates*

Self-consistent modeling of astrophysical systems involving black hole accretion disks and neutron stars is quite computationally intensive, requiring that we solve the general relativistic hydrodynamics (GRHD) equations. In the case of dynamical spacetimes, the GRHD equations must be coupled to the GR field equations as well. We address these challenges with GRoovy: a new GRHD code that extends the General Relativistic Hydrodynamics Library (GRHayL). This extension, built within the NRPy+ framework, supports a reference-metric-based formulation of the GRHD equations and the BSSN formulation in singular curvilinear coordinates. Leveraging this approach allows us to exploit near symmetries in black hole accretion disks and neutron star evolutions, greatly improving the efficiency over Cartesian AMR approaches. Given GRHayL's existing robust implementations for reconstruction algorithms, conservative-to-primitive solvers, finite-temperature microphysical equations of state, and neutrino physics, our new code is well-equipped for state-of-the-art simulations. In this report, we present multi-dimensional tests that showcase the accuracy and efficiency of our code.