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arXiv · 2512.15846

GRHayL: a modern, infrastructure-agnostic, extensible library for GRMHD simulations

Samuel Cupp·Leonardo R. Werneck·Terrence Pierre Jacques·Samuel Tootle·Zachariah B. Etienne
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Abstract

Interpreting multimessenger signals from neutron stars and black holes requires reliable general relativistic magnetohydrodynamics (GRMHD) simulations across rapidly evolving high-performance computing platforms, yet key algorithms are routinely rewritten within infrastructure-specific numerical relativity codes, hindering verification and reuse. We present the General Relativistic Hydrodynamics Library (GRHayL), a modular, infrastructure-agnostic GR(M)HD library providing conservative-to-primitive recovery, reconstruction, flux/source and induction operators, equations of state, and neutrino leakage through an intuitive interface. GRHayL refactors and extends the mature IllinoisGRMHD code into reusable point- and stencilwise kernels, enabling rapid development and cross-code validation in diverse frameworks, while easing adoption of new microphysics and future accelerators. We implement the same kernels in the Einstein Toolkit (Carpet and Carpetx) and BlackHoles@Home, demonstrating portability with minimal duplication. Validation combines continuous-integration unit tests with cross-infrastructure comparisons of analytic GRMHD Riemann problems, dynamical Tolman-Oppenheimer-Volkoff evolutions, and binary neutron star mergers, showing comparable or improved behavior over legacy IllinoisGRMHD and established Einstein Toolkit codes.

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Samuel Cupp, Leonardo R. Werneck, Terrence Pierre Jacques, Samuel Tootle, Zachariah B. Etienne. 2025-12-17. GRHayL: a modern, infrastructure-agnostic, extensible library for GRMHD simulations. https://doi.org/10.1103/bbtm-31r5

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