Theoretical Studies in Gravitation and Astrophysics

该奖项支持相对论和相对论天体物理学的研究，并解决了NSF“宇宙之窗”大构想的优先领域。LIGO/Virgo科学合作组织编制了一份令人印象深刻的引力波（GW）事件列表，其中包括几十个双黑洞（BHBH）合并，一对双中子星（NSNS）合并和几个可能的黑洞-中子星（BHNS）合并。这些探测标志着GW天文学时代的开始。本研究项目涉及广义相对论、gw的产生、相对论流体力学和相对论磁流体力学等问题。连接不同理论主题的一条共同线索是引力，特别是相对论引力的关键作用。紧凑的物体（黑洞、中子星和白矮星）提供了主要的论坛，强引力场中的物质动力学是一个主要的主题。一些研究课题包括紧致双星（bhbhhs， NSNSs和BHNSs）的激发和聚并；由合并双星和其他有希望的天体物理源产生的gw，以及它们对应的电磁信号；引力坍塌;旋转的相对论恒星的稳定性和不稳定恒星的演化和最终命运；伽马暴源；超大质量恒星（SMSs）磁旋转坍缩导致的超大质量黑洞（SMBHs）的形成和成长等场景；围绕星系和类星体核心的合并双星SMBHs的环双星盘；星系核心（包括银河系）中SMBHs周围暗物质的轮廓和可观测特征，以及包含DM、恒星和SMBHs的星团的动态演化。该结果对天文观测具有重要意义，包括由GW干涉仪收集和/或计划用于GW干涉仪的观测。这些主题大多代表了理论物理中长期存在的基本问题，需要大规模的计算来解决。因此，除了分析建模之外，该方法在很大程度上还涉及在超级计算机上进行大规模模拟。关键工具将是稳健且经过良好测试的伊利诺伊广义相对论磁流体动力学（GRMHD）代码。模拟求解了引力的爱因斯坦广义相对论场方程、流体的相对论MHD方程和电磁场的麦克斯韦方程组。这些方程构成了高度非线性的、耦合的3+1维偏微分方程，用有限差分法求解。伊利诺伊州GRMHD代码采用Baumgarte-Shapiro-Shibata-Nakamura （BSSN）技术，采用移动穿刺计条件和自适应移动网格细化来求解场方程和MHD的高分辨率冲击捕获方案。要解决的问题包括初始值和进化计算，并处理包含黑洞的真空时空，以及包含现实物质源，磁场以及EM和中微子辐射的时空（“多信使天文学”）。这项拨款支持的研究和推广活动有助于促进计算机和可视化工具在各级教育中的使用，以及公众对引力物理学和天体物理学中一些最新和最令人兴奋的发展的认识。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award supports research in relativity and relativistic astrophysics and it addresses the priority areas of NSF's "Windows on the Universe" Big Idea. The LIGO/Virgo Scientific Collaboration has compiled an impressive list of detected gravitational wave (GW) events consisting of several dozen binary black hole (BHBH) mergers, a couple of binary neutron star (NSNS) mergers and several likely black hole--neutron star (BHNS) mergers. These detections mark the beginning of the era of GW astronomy. This research project spans several problems involving general relativity (GR), the generation of GWs, relativistic hydrodynamics, and relativistic magnetohydrodynamics. A common thread uniting the different theoretical topics is the crucial role of gravitation, especially relativistic gravitation. Compact objects (black holes, neutron stars and white dwarfs) provide the principal forum, and the dynamics of matter in a strong gravitational field is a major theme. Some of the topics for investigation include the inspiral and coalescence of compact binaries (BHBHs, NSNSs and BHNSs); the generation of GWs from merging binaries and other promising astrophysical sources, and their counterpart electromagnetic (EM) signals; gravitational collapse; the stability of rotating, relativistic stars and the evolution and final fate of unstable stars; gamma-ray burst sources (GRBs); the formation and growth of supermassive black holes (SMBHs) from the magnetorotational collapse of supermassive stars (SMSs) and other scenarios; circumbinary disks around merging binary SMBHs in the cores of galaxies and quasars; and the profiles and observable signatures of dark matter around SMBHs in galaxy cores, including the Milky Way, and the dynamical evolution of clusters containing DM, stars and SMBHs. The results have important implications for astronomical observations, including those collected by and/or planned for GW interferometers.Most of these topics represent long-standing, fundamental problems in theoretical physics requiring large-scale computation for solution. Hence the approach involves to a significant degree large-scale simulations on supercomputers, in addition to analytical modeling. The key tool will be the robust and well-tested Illinois general relativistic, magnetohydrodynamic (GRMHD) code. The simulations solve Einstein's field equations of GR for gravity coupled to the equations of relativistic MHD for the fluid and Maxwell's equations for the EM fields. These equations constitute highly nonlinear, coupled partial differential equations in 3+1 dimensions that are solved by finite-differencing. The Illinois GRMHD code employs the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) technique with moving puncture gauge conditions and adaptive moving mesh refinement to solve the field equations and a high-resolution, shock capturing scheme for the MHD. The problems to be tackled comprise both initial value and evolution computations and treat vacuum spacetimes containing black holes, as well as spacetimes containing realistic matter sources, magnetic fields and both EM and neutrino radiation ("multimessenger astronomy"). The research and outreach activities supported by this grant help promote the use of computers and visualization tools at all levels of education, as well as the public awareness of some the latest and most exciting developments in gravitational physics and astrophysics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.