RUI: Studies in Numerical Relativity

爱因斯坦的广义相对论描述了宇宙中所有的引力相互作用，从把落下的苹果拉到地球上的力，到宇宙本身的膨胀。特别是，这一理论描述了黑洞和中子星--即所谓的具有极强引力场的“致密物体”。这个奖项的目的是研究当这样的物体与更大的恒星相撞时会发生什么：这样的碰撞是可观察到的吗？碰撞的残余物是否会形成一种新类型的恒星，或者它会坍塌形成另一个黑洞，可能在一个不寻常的质量范围内？这些问题的答案将有助于揭示大量致密天体，包括可能在早期宇宙中形成并可能对其暗物质含量做出贡献的极小黑洞，并有助于理解LIGO引力波探测器最近对具有异常质量的黑洞的观测。找到这些答案需要数值相对论的工具，即可以从数值上找到爱因斯坦广义相对论方程的解的计算机程序。本科生将参与这些活动，为他们提供实践的研究体验，并在鲍登学院创造一个丰富的研究学习环境。这些研究工作的科学目标包括开发和实施求解爱因斯坦广义相对论方程的数值算法，以及它们在相对论物体，特别是中子星和黑洞的数值模拟中的应用。在下一个资助期，这些活动的重点将是所谓的“索恩-兹特科夫类天体”，即较大的“宿主”恒星，它们拥有较小的致密天体作为“寄生虫”。例如，有可能是原始起源的小黑洞的中子星，有中子星的白矮星，以及有黑洞或中子星的主序星。具体的研究活动将探索这些天体可能形成的过程，包括捕获和/或双星合并，并将确定它们是否动态稳定，它们的共同演化和最终坍塌是否导致可观察到的引力波或电磁信号，以及这些场景是否为标准恒星演化导致的质量范围外的黑洞提供可行的演化路径。该奖项反映了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。

Einstein’s theory of general relativity describes all gravitational interactions in the universe, ranging from the force that pulls a falling apple to the Earth, to the expansion of the Universe itself. In particular, this theory describes black holes and neutron stars — so-called "compact objects" that have extremely strong gravitational fields. The goal of this award is to study what happens when such an object collides with a larger star: would such a collision be observable, would the remnant of the collision form a new type of star, or would it collapse to form another black hole, possibly in an unusual mass range? Answers to these questions will help shed light on the abundance of compact objects, including very small black holes that may have formed in the early Universe and that may contribute to its dark-matter content, and will help understand recent observations by the LIGO gravitational wave detectors of black holes with unusual masses. Finding these answers requires the tools of numerical relativity, i.e. computer programs that can find solutions to Einstein’s equations of general relativity numerically. Undergraduate students will participate in these activities, providing them with a “hands-on” research experience, and generating a research-enriched learning environment at Bowdoin College.The scientific goals of these research efforts include the development and implementation of numerical algorithms for the solution of Einstein's equations of general relativity, as well as their application in the numerical modeling of relativistic objects, in particular neutron stars and black holes. In the next funding period these activities will focus on so-called "Thorne-Zytkow-like-Objects", i.e. larger "host" stars that harbor smaller compact objects as "parasites". Examples include neutron stars that harbor small black holes, possibly of primordial origin, white dwarfs that harbor neutron stars, and main sequence stars that harbor black holes or neutron stars. Specific research activities will explore processes by which these objects may form, including capture and/or binary merger, and will determine whether or not they are dynamically stable, whether their co-evolution and ultimate collapse results in observable gravitational-wave or electromagnetic signals, and whether these scenarios provide viable evolutionary pathways to black holes outside the mass ranges resulting from standard stellar evolution.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.