发表机构
School of Natural Sciences, Institute for Advanced Study; Princeton Gravity Initiative, Princeton University（高等研究院自然科学学院; 普林斯顿大学引力倡议）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文在 AthenaK 中实现了基于 tetrad 变换的广义相对论 HLLD 求解器，通过初始猜测和通量校正提升性能与鲁棒性，在 SANE 盘和双中子星并合中展现优势，成本略高于 HLLE。
AI 中文摘要
我们展示了在 AthenaK 天体物理学代码中实现 HLLD 近似黎曼求解器，并通过 tetrad 框架变换支持完整的广义相对论磁流体动力学。我们的实现使用 HLLD 迭代求解的初始猜测，消除了额外守恒-原初变量反演的需要，从而在不影响精度的情况下大大加速了性能。此外，通过将该方法与一阶通量校正相结合，我们能够在磁化强度超过 $10^4$ 时可靠地使用该方法，我们在 SANE 吸积盘中实现了这一点。我们的 SANE 盘表明，与 HLLE 相比，HLLD 导致更强的磁化漏斗和更精确的视界通量。我们进一步将新的 HLLD 实现应用于等质量双中子星并合。对于我们的长寿命残骸，HLLD 增强了外层中的磁剪切应力，并导致较弱的较差自转。然而，由于并合后阶段引力波辐射较弱，残骸始终较不致密，同时产生更多的动力学抛射物和更庞大的盘。得益于改进的初始猜测，这个新求解器的成本相对适中：我们的吸积盘测试仅比 HLLE 慢约 $10-25\%$，而对于我们使用微物理状态方程的双中子星运行，我们发现 HLLD 在所有运行中仅比 HLLE 慢约 $3\%$。
英文摘要
We present an implementation of an HLLD approximate Riemann solver for the AthenaK astrophysics code with support for full general relativistic magnetohydrodynamics via a tetrad frame transformation. Our implementation uses an initial guess for the HLLD iterative solve which eliminates the need for an additional conserved-to-primitive inversion, which greatly accelerates performance without affecting accuracy. Additionally, by coupling the method with a first-order flux correction, we are able to use the method reliably even when the magnetization exceeds $10^4$, which we achieve in a SANE accretion disk. Our SANE disk shows that HLLD leads to a more strongly magnetized funnel and more accurate horizon fluxes when compared with HLLE. We further apply the new HLLD implementation to an equal-mass binary neutron star merger. For our long-lived remnant, HLLD enhances the magnetic shear stresses in the outer layers and leads to weaker differential rotation. However, due to weaker gravitational wave emissions in the post-merger phase, the remnant is consistently less compact while producing more dynamical ejecta and a more massive disk. The cost of this new solver is relatively modest thanks to the improved initial guess: our accretion disk tests are only ${\sim}10-25\%$ slower than HLLE, and for our binary neutron star runs with a microphysical equation of state, we find that HLLD is only ${\sim}3\%$ slower than HLLE across all runs.
Comments19 pages, 15 figures
