Collaborative Research: Deploying Curvilinear Coordinate and Multipatch Methods on Neutron Star Mergers

该奖项支持相对论和相对论天体物理学的研究，并阐述了美国国家科学基金会“宇宙之窗”宏伟构想的优先领域。最近使用引力波干涉仪和电磁望远镜的全谱观测到的双中子星合并，开启了万用站天文学和天体物理学的时代。LIGO、处女座和其他即将到来的类似干涉仪和主要天文设施迅速增加的新GW探测速度，预计将在不久的将来从这些来源带来前所未有的丰富的观测证据。这一奖项将资助罗切斯特理工学院和约翰霍普金斯大学合作研究中子星合并的后期阶段，特别是坍塌为黑洞和稳定中子星的长寿命超大质量中子星。这项工作还包括开发这些计算所需的新计算工具。将特别注意状态方程和总质量作为诸如磁场等最终性质的决定因素所起的作用。由于磁场既支持吸积又支持喷流，所以磁场在很大程度上掩盖了所发生的一切。对一系列天体物理事件的模拟，包括电磁波和引力波信号的强来源，将需要能够处理越来越广泛的微物理处理、特征尺度和复杂程度的数值工具。另一方面，许多天体物理系统表现出近似的对称性，可以用来降低总的计算成本。通过选择反映近似对称性的坐标拓扑或多个坐标面片，可以在较低的计算成本下获得较高的模拟精度。球极网格最适合相对论天体物理中的许多应用。然而，这些方法往往严重的库兰特稳定性限制，使它们的成本高得令人望而却步。这个项目是开发新的编码基础设施来克服这些限制，并应用它们来执行高精度，但也非常快的超大质量中子星残骸的模拟。另一方面，多面体方法虽然计算比单个球面面片复杂，但非常适合于模拟这些紧凑物体周围的射流。除了开发新的算法外，该奖项还将用于培训高度并行计算方面的博士后和研究生。它还将为学生提供多信使天文学和高性能计算方面的教育材料，并通过各种渠道加强公众宣传，包括多信使天文学的REU计划和为未被充分代表的少数族裔本科生提供物理研究经验的暑期计划。本科生科学教育的改进将带来更多的教育利益。拟议模拟的科学可视化将通过年度社区范围的公共展览，作为关于科学和计算的公共宣传活动的工具。这也将给更广泛的科学界带来好处：新的模拟工具和输出数据集都将被公开。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势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 recent observations of a binary neutron star merger using both gravitational wave interferometers and the full spectrum of electromagnetic telescopes has initiated the age of multimessenger astronomy and astrophysics. The rapidly increasing rate of new GW detections by LIGO, VIRGO, and other upcoming similar interferometers and major astronomical facilities is expected to bring an unprecedented wealth of observational evidence from these sources in the near future. This award will fund a collaborative research effort at the Rochester Institute of Technology and the Johns Hopkins University into the latter stages of neutron star mergers, in particular long-lived hypermassive neutron stars that collapse to black holes and stable neutron stars. The effort also includes development of new computational tools required for these calculations. Particular attention will be paid to the roles of the equation of state and total mass as determinants of final properties such as magnetic fields. Magnetic fields underly much of what happens because they support both accretion and jets.Simulations of a wide range of astrophysical events, including strong sources of both electromagnetic and gravitational wave signals, will require numerical tools that can handle an increasingly wide range of microphysical treatments, characteristic scales, and levels of complexity. On the other hand, many astrophysical systems exhibit approximate symmetries that can be leveraged to reduce the total computational cost. By choosing coordinate topologies that mirror the approximate symmetries, or multiple coordinate patches, one can obtain higher simulation accuracies at lower computational costs. Spherical polar grids are optimally suited for a host of applications in relativistic astrophysics. However, the often severe Courant stability limitation of these methods have made them prohibitively expensive. This project is to develop new coding infrastructures to overcome these limitations and apply them to perform highly-accurate, but also very fast simulations of hypermassive neutron star remnants. On the other hand, multipatch method, while computational more complex than single spherical patches, are ideal for simulations of jets around these compact objects. In addition to developing new algorithms, this award will be used train a postdoc and a graduate student in highly-parallelized computing. It will also provide material for educating students in multimessenger astronomy and high-performance computing, and enhance public outreach through a variety of channels, including both an REU program in multimessenger astronomy and a summer program giving underrepresented minority undergraduates experience in physics research. Further educational benefits will accrue through improvements in undergraduate science education. Scientific visualizations from the proposed simulations will be used as a vehicle for public outreach events on science and computing through annual community-wide public exhibits. There will also be benefits to the broader scientific community: both the new simulation tools and the output data sets will be made public.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.