标题： 并非所有广义相对论光线追踪的时空坐标都是相同的 显示英文标题

标题： Not all spacetime coordinates for general-relativistic ray tracing are created equal

摘要： 用于天体物理黑洞观测外观的模型关键依赖于精确的广义相对论光线追踪和辐射传输，以计算远处观察者测得的强度。 在本文中，我们说明坐标选择和初始条件如何影响这一过程。 特别是，我们表明，如果光子的空间动量指向事件视界或远离事件视界，从相机到光源传播光线会导致不同的解。 在此过程中，我们还表明，适用于数值广义相对论磁流体动力学（GRMHD）模拟的坐标通常不是通用光线追踪的最佳选择。 我们讨论了对黑洞图像的影响，并表明在最优和非最优时空坐标中的辐射传输会导致相同的图像，仅受数值误差和算法选择的影响。 显示英文摘要

摘要： Models for the observational appearance of astrophysical black holes rely critically on accurate general-relativistic ray tracing and radiation transport to compute the intensity measured by a distant observer. In this paper, we illustrate how the choice of coordinates and initial conditions affect this process. In particular, we show that propagating rays from the camera to the source leads to different solutions if the spatial part of the momentum of the photon points towards the horizon or away from it. In doing this, we also show that coordinates that are well suited for numerical General-Relativistic MagnetoHydroDynamic (GRMHD) simulations are typically not optimal for generic ray tracing. We discuss the implications for black-hole images and show that radiation transport in optimal and non-optimal spacetime coordinates lead to the same images up to numerical errors and algorithmic choices.