Numerical studies of compact object binaries

引力波是空间和时间上的涟漪，它给我们带来了宇宙中最剧烈事件的信息：黑洞或中子星的碰撞，超新星和大爆炸本身。在过去的十年里，引力波探测器已经建成，最著名的是美国先进激光干涉仪引力波天文台（LIGO）。这些探测器计划最早在2015年开始搜寻引力波。第一个GW的发现将是一个分水岭事件，类似于最近发现的希格斯玻色子。不那么引人注目，但可以说更重要的是随后进一步的GW观测流，这将对我们的宇宙产生深远的见解：观察到的致密物体合并是否符合广义相对论？大质量恒星是如何死亡的，它们留下了什么样的致密物体？物质在超核密度下表现如何？黑洞和中子星在星系中心附近和球状星团中是如何相互作用的？这场革命需要对预期的引力波有精确的了解，而这只能从超级计算机计算中获得。知道预期引力波的形状可以发现较弱的引力波，增加将被观测到的引力波的数量。要确定引力波起源的精确信息，也需要了解引力波的波形：例如，黑洞和中子星的质量和旋转速度，以及它们在宇宙中的位置。Pfeiffer教授和他在CITA的研究小组在黑洞和中子星碰撞的计算机模拟以及将其结果应用于引力波天体物理学方面处于世界领先地位。与美国的合作者一起，他们开发了一种杰出的计算机代码来模拟致密物体的碰撞，并对碰撞黑洞进行了最详尽的研究。Pfeiffer教授的团队还参与了LIGO科学合作项目，在那里领导开发低延迟搜索管道，可以在几分钟内确定引力波是否穿过望远镜。该提案寻求资金来继续这个研究小组，以确保LIGO能够尽可能快地发现引力波，尽可能灵敏，并且能够以最小的偏差确定发射引力波的物体的特性。这个研究项目涵盖了一系列相互交织的主题。我们建议继续我们擅长的工作：执行二进制黑洞计算并基于这些模拟构建波形模板。鉴于菲佛目前的发现基金所取得的成就，准圆形黑洞双星的完整解决方案似乎是可行的，这也是我们的目标。我们建议扩展到对偏心双黑洞的调查。这样的系统——如果存在的话——必须以与准圆双星截然不同的方式形成，并表现出准圆双星所没有的特性。不幸的是，偏心双星更难被探测到。我们的模拟将有助于探测它们，至少可以量化LIGO对这些源的实际敏感程度。我们建议加强对LIGO搜索工作的直接参与。最后，我们建议开发一种新的，下一代相对论天体物理代码，它消除了当前代码的限制。这将成为这个研究小组未来世界一流科学的基础。各种各样的目标平衡了LIGO对首次突破性发现的迫切需求和长期科学领导的战略发展。我们要求为该研究项目提供约60%的资金，剩余部分预计将来自其他来源。

Gravitational waves are ripples in space and time which carry information to us about the most violent events in the universe: Collisions of black holes or neutron stars, supernovae and the big bang itself. During the last decade gravitational wave detectors have been built, most notably the U.S. Advanced Laser Interferometer Gravitational Wave Observatory (LIGO). As early as 2015 these detectors plan to begin searches for gravitational waves. The first GW discovery will be a watershed event, similar to the recent discovery of the Higgs boson. Less dramatic, but arguably even more important will be the subsequent stream of further GW observations, which will yield far-reaching insights into our Universe: Are the observed compact object mergers consistent with general relativity? How do massive stars die, and what compact objects do they leave behind? How does matter behave at supernuclear densities? How do black holes and Neutron stars interact near the centres of galaxies and in globular clusters? This revolution requires precise knowledge of the expected gravitational waves, which can only be obtained from supercomputer calculations. Knowing the shape of the expected waves allows to find weaker waves, increasing the number of gravitational waves that will be observed. Knowledge of the waveform is also required to determine the precise information about the origin of the wave: for instance, the masses and rotation rates of black holes and neutron stars, their location in the universe. Prof. Pfeiffer and his research group at CITA are world-leaders in computer simulations of colliding black holes and neutron stars, and in applying their results to gravitational wave astrophysics. With collaborators in the U.S. they have developed an outstanding computer code to simulate colliding compact objects, and have performed the most exhaustive study of colliding black holes. Prof. Pfeiffer’s group also participates in the LIGO Scientific Collaboration where it leads the development of low-latency search pipelines that can decide within minutes whether gravitational waves have passed through the telescopes. This proposal seeks funding to continue this research group to ensure LIGO will discover gravitational waves as quickly as possible, will be as sensitive as possible, and will be able to determine, with minimal bias, the properties of the objects emitting the gravitational waves. This research program spans a gamut of interwoven themes. We propose to continue what we do well: Perform binary black hole calculations and construct waveform templates based on these simulations. Given the accomplishments of Pfeiffer’s present Discovery Grant, the complete solution for quasi-circular black hole binaries appears feasible, and is our objective. We propose to expand into a survey of eccentric binary black holes. Such systems -if they exist- must form in profoundly different ways than quasi-circular binaries, and exhibit properties that are absent in quasi-circular binaries. Unfortunately, eccentric binaries are much more difficult to detect. Our simulations will aid in detecting them and –at the least– allow to quantify how sensitive LIGO actually is to such sources. We propose to intensify direct participation in LIGO’s search efforts. Finally, we propose to develop a novel, next generation relativistic astrophysics code which removes limiting restrictions of the current code. It will be the foundation for future world-class science from this research group. The variety of objectives balances immediate needs of LIGO for the first breakthrough discovery with strategic development of long-term scientific leadership. We request funding for about 60% of this research program, with the remainder anticipated from other sources.