A new code to solve the equations of general relativistic hydrodynamics in singular curvilinear coordinates using GRHayL*

We report on the development of a new open-source code that solves the equations of general relativistic hydrodynamics (GRHD) in singular curvilinear coordinates. This code extends the General Relativistic Hydrodynamic Library (GRHayL) to support reference-metric-based formulations of the GRHD equations within the NRPy+ framework. Building on the existing capabilities within GRHayL, this extension will enable us to exploit near symmetries to perform extremely efficient simulations of systems of astrophysical interest, including neutron stars (nearly spherically symmetric or axisymmetric), black hole accretion disks (nearly axisymmetric), etc. As GRHayL already provides robust implementations of reconstruction algorithms, conservative-to-primitive solvers, finite-temperature microphysical equations of state, and neutrino physics, this code will be capable of state-of-the-art simulations. Here we present our progress and multi-dimensional tests validating our code.