WOU-MMA: Gravitational Radiation and Relativistic 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。激光干涉仪引力波天文台（LIGO）现在正在反复探测引力波（GWs）——空间和时间上的涟漪——由距离地球数百万光年，有时甚至数十亿光年的致密物体碰撞发出。这些物体中的大多数是黑洞，其他的是中子星。从GWs中，科学家可以测量物体的属性（位置、质量、自旋），并了解它们可能是如何形成的，以及它们在碰撞时如何扭曲空间和时间；对于中子星来说，碰撞也会产生伽马射线和其他电磁辐射，与GWs一起，这告诉科学家物质在超高密度下的行为以及一些化学元素是如何形成的。但是这些研究需要将探测到的gw与对引力波的详细预测进行比较。这些预测是根据广义相对论做出的，广义相对论是爱因斯坦在1915年写下的，但直到2005年，随着先进方法和强大超级计算机的发展，才得以解决（对于致密物体的碰撞）。该项目支持理论工作，旨在巩固和提高LIGO从观测到的GWs中提取丰富信息的能力，并通过电磁对口改进对LIGO事件的解释。这包括改进和使用光谱爱因斯坦代码（SpEC），这是目前解决爱因斯坦黑洞双星方程的最精确的计算机代码。SpEC将用于进行黑洞碰撞的数值解，以分析LIGO数据。此外，正在开发的下一代计算机代码SpECTRE将用于预测两颗中子星碰撞和黑洞与中子星碰撞产生的gw，并将用于研究合并后形成的吸积盘。该项目还将成为年轻物理学家和天体物理学家的培训基地。新代码SpECTRE及其输出将公开发布。小组成员将通过讲座、互动网页和YouTube视频与公众接触。通过将分析技术和数值模拟与谱爱因斯坦代码（SpEC）相结合：(i)将生成BBH的GW信号，用于在BBH参数空间的未开发区域进行LIGO数据分析，并将用于生成数值替代模型，该模型可以在毫秒内评估单个波形，同时保留完整数值模拟的准确性；（ii）高度弯曲时空的动力学行为将通过解析、微扰和数值方法进行探索，其中将包括准正规模式激发、奇异致密物体、超越爱因斯坦引力理论和极端质量比吸气的研究。分析技术和下一代开源代码SpECTRE的结合将应用于BHNS和NSNS二进制和吸积盘的研究，以了解多信使事件。这将包括对合并后吸积盘和潮汐耦合的研究。我们将研究地面和天基探测器可能探测到的信号的参数估计，并探索未来可能的十赫兹引力波探测器的科学案例。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 Laser Interferometer Gravitational-Wave Observatory (LIGO) is now repeatedly detecting gravitational waves (GWs)---ripples in space and time---emitted by the collision of compact objects millions, sometimes billions, of light-years from Earth. Most of these objects have been black holes, others have been neutron stars. From the GWs, scientists can measure properties (locations, masses, spins) of the objects and learn about how they might have formed and how they warp space and time as they collide; for neutron stars, the collision also produces gamma-rays and other electromagnetic radiation, and together with the GWs this teaches scientists how matter behaves at ultra-high densities and how some chemical elements were formed. But these studies require comparing the detected GWs with detailed predictions of the waves. The predictions are made using the equations of General Relativity, written down by Einstein in 1915 but unsolvable (for colliding compact objects) until about 2005 with the development of advanced methods and powerful supercomputers. This project supports theoretical work designed to underpin and improve LIGO's ability to extract from observed GWs the rich information that the waves carry, and to improve the interpretation of LIGO events with electromagnetic counterparts. This includes the improvement and use of the Spectral Einstein Code (SpEC), currently the most accurate computer code for solving Einstein's equations for black hole binaries. SpEC will be used to carry out numerical solutions of black-hole collisions for the purpose of analyzing LIGO data. In addition, a next-generation computer code SpECTRE, under development, will be used to predict GWs from two colliding neutron stars and from a black hole colliding with a neutron star, and will be used to study accretion disks that form after the merger. This program will also serve as a training ground for young physicists and astrophysicists. The new code SpECTRE and its output will be publicly released. The group members will reach out to the general public through lectures, interactive web pages, and YouTube videos.By combining analytical techniques and numerical simulations with the Spectral Einstein Code (SpEC): (i) GW signals for BBHs will be generated for use in LIGO data analysis in poorly-explored regions of the BBH parameter space, and will be used to produce numerical surrogate models that can evaluate a single waveform in milliseconds while retaining the accuracy of full numerical simulations; and (ii) the dynamical behavior of highly curved spacetime will be explored via analytic, perturbative, and numerical approaches, which will include studies of quasinormal mode excitations, exotic compact objects, beyond-Einstein theories of gravitation, and extreme mass ratio inspirals. A combination of analytic techniques and the next-generation open-source code SpECTRE will be applied to studies of BHNS and NSNS binaries and accretion disks to understand multi-messenger events. This will include investigations of post-merger accretion disks and tidal coupling. Parameter estimation will be investigated for signals that might be detected by both ground-based and space-based detectors, and the science case for possible future deci-Hertz gravitational-wave detectors will be explored.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.