Collaborative Research: Testing General Relativity with Gravitational-Wave Observations

密西西比大学（University of Mississippi）和宾夕法尼亚州立大学（Pennsylvania State University）的研究小组合作，将利用LIGO和世界各地其他探测器即将观测到的数据，对爱因斯坦的空间、时间和引力理论进行新的精确测试。爱因斯坦的广义相对论是一个非常成功的物理学理论，他对光的弯曲的预言在100多年前被亚瑟·爱丁顿爵士证实。同样的理论预言了引力波的存在——引力波是一种新的辐射，在极端的天文现象中产生，比如黑洞碰撞。2015年9月14日，美国国家科学基金会的激光干涉仪引力波天文台（LIGO）首次探测到两个黑洞碰撞产生的引力波。从那时起，已经观察到近100次这样的事件。黑洞碰撞产生的引力波是检验爱因斯坦理论是否正确描述时空和引力的最佳依据。尽管爱因斯坦的理论在解释精确的地面实验和天文观测方面非常成功，但仍有迹象表明该理论是不完整的。密西西比大学（University of Mississippi）和宾夕法尼亚州立大学（Penn State）的研究人员发现了一种方法，可以将来自多个事件的数据结合起来，以提高所用方法的有效性。他们将利用复杂的统计推断工具来确定结果是可靠的，具有高置信度，但同时要确保数据中的噪声伪像和其他不相关的物理效应不会被误解为理论的失败。这些小组将在标准的科学实践和先进的分析技术方面培训学生，并为他们提供一个与全球引力波天文学专家合作的平台。该团队还将在“极限”研讨会上组织物理学和天体物理学，通过小组讨论和头脑风暴会议激发新颖的想法。在接下来的三年里，LIGO、Virgo和KAGRA探测引力波的灵敏度得到了提高，它们将能够探测到数百颗碰撞的中子星和黑洞。这些碰撞将向引力波释放大量能量，探测到的信号以前所未有的细节携带着相对论引力的特征，并有可能证伪广义相对论（GR）。由于GR在解释观测和实验结果方面取得了巨大的成功，因此该理论正确的先验概率非常高。伪造GR将需要可靠的统计推断，以解释用于检测和测量以及减轻由非平稳噪声引起的伪像的波形模型中缺失的物理。例如，目前的大多数测试都假设双黑洞在真空中处于准圆形轨道上，但这并不一定正确。本研究的主要目的是加强利用奇异值分解的GR标准测试，并利用发射波的多极结构实现一种新的测试。这些改进的测试可以揭示高保真信号中存在的GR违规。然而，至关重要的是，要有一个可能被误解为违反GR的系统性影响的全面列表。第二个主要目标是收集这样一个列表，探索它们对各种GR测试的影响，并为解决假警报做好准备。这种双管齐下的方法加强了合作进行的GR测试的影响，同时为发现新的物理现象做好了准备，如果它出现在数据中。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。

A collaboration between research groups at the University of Mississippi and Pennsylvania State University will use data from upcoming observations of LIGO and other detectors around the world to subject Einstein’s theory of space, time and gravity to new precision tests. Einstein’s General Theory of Relativity has been a highly successful theory of physics whose prediction of the bending of light was famously confirmed by Sir Arthur Eddington more than a hundred years ago. That same theory predicted the existence of gravitational waves–a new kind of radiation that is produced in extreme astronomical phenomena such as colliding black holes. On September 14, 2015, NSF's Laser Interferometer Gravitational-wave Observatory (LIGO) detected for the first-time gravitational waves from two colliding black holes. Since then, almost 100 such events have been observed. Gravitational waves from colliding black holes are the best grounds for testing if Einstein’s theory is the correct description of spacetime and gravity. Although Einstein’s theory has been remarkably successful in explaining precision terrestrial experiments and astronomical observations, there are hints that the theory is incomplete. Researchers at the University of Mississippi and Penn State have found a way to combine data from multiple events to increase the efficacy of the methods used. They will make use of sophisticated statistical inference tools to ascertain that the results are sound and are of high confidence, but at the same time make sure that noise artifacts in the data and other unrelated physical effects are not misinterpreted as a failure of the theory. The groups will train students in standard scientific practices and advanced analysis techniques and provide them with a platform to work with experts in gravitational wave astronomy globally. The team will also organize Physics and Astrophysics at the 'eXtreme' workshops to stimulate novel ideas via panel discussions and brainstorming sessions.The improved sensitivities of LIGO, Virgo, and KAGRA to detect gravitational waves over the next three years will allow the detection of hundreds of colliding neutron stars and black holes. These collisions will release vast amounts of energy into gravitational waves and the detected signals carry the signature of relativistic gravity in action in unprecedented detail and will have the potential to falsify general relativity (GR). Due to the enormous success of GR in explaining observational and experimental results, the prior probability that the theory is correct is very high. Falsifying GR will require robust statistical inference that accounts for missing physics in the waveform models used in detection and measurement and mitigation of artifacts due to non-stationary noise. For example, most of the current tests assume that binary black holes are in quasi-circular orbits in vacuum, but this is not necessarily true. The principal goal of the study is to strengthen the standard tests of GR using singular value decomposition and to implement a new test utilizing the multipole structure of the emitted waves. These refined tests could reveal GR violations present in high-fidelity signals. It is vital, however, to have a comprehensive list of systematic effects that could be misinterpreted as a GR violation. The second principal goal is to assemble such a list, explore their effect on the various tests of GR, and prepare the collaboration to account for false alarms. This two-pronged approach reinforces the impact of the tests of GR undertaken by the collaborations, while preparing the path to discovering new physics should it show up in the data.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.