引力波与引力理论的观测检验

In 2016, LIGO Collaboration claimed the discovery of gravitational-wave signal for the first time by the direct observations, which marks the birth of gravitational-wave astrophysics. One of the most important application of gravitational wave is the experimental tests of gravitational theories in the strong gravitational field. Until now, Einstein's General Relativity is the most successful gravitational theory. However, the studies on the modified gravities are still the popular research area, which is caused by the fact that scientists can never truely "prove" General Relativity is correct, but rather all we do is disprove, or more accurately constrain, alternative hypothesis. In this project, we will focus on the following three parts: (1) Choosing the typical modified gravities and calculating the Parameterized Post-Newtonian parameters. Then we constrain the models by the tests in solar system and cosmology. (2) Based on these results, we calculate the orbital decay of the compact binary systems in these theories caused by the gravitational radiations, and constrain the theory by the observations. (3) Calculating the gravitational waves in the binary systems including their amplitude, phase and polarizations. Then, we study the possibility to constrain the theories by LIGO and Pulsar Timing Array observations. By these three related parts, in this project we will study the experimental tests of gravitational theories in the strong gravitational fields.

2016年，美国的LIGO工作组宣布首次直接探测到了引力波信号，这标志着引力波天文物理学这门新学科的诞生。引力波的一个非常重要的应用，就是使得人们可以在强引力场中对引力理论进行观测检验。虽然，到目前为止，爱因斯坦的广义相对论仍然是最成功的引力理论，但是对修改引力波的研究仍然是目前理论和实验研究的热门，这是因为相对论本身不可能从实验上被验证，只有在与其它引力预言的比较中才能一步步被检验。在本项目中，我们就以下三个问题开展研究：（1）选择具有典型特征的修改引力理论，计算其后牛顿参数以及其太阳系和宇宙学限制；（2）在此基础上，我们详细计算致密双星系统的引力辐射导致的双星轨道衰变，通过与观测比较来限制修改引力；（3）计算修改引力中双星引力辐射的波形、相位和极化，通过激光干涉仪和脉冲星即使阵列来限制该引力。上述三个部分紧密相关，互为基础，通过在理论和观测上与相对论预言比较在强引力场中检验引力理论。

在基金委面上项目“引力波与引力理论的观测检验”的大力支持下，研究团队紧密围绕引力波与引力检验这个主题，深入研究了引力波天文与物理学的多个相关方面，包括引力波数据分析及其引力的强场检验、原初引力波及其探测研究、引力波源及其宇宙学应用等方面的内容。在过去四年内，本团队紧密围绕这几个研究方向，在通过分析现有的和未来的引力波数据限制各种修改引力波模型包括屏蔽修改引力，宇称不对称引力，Brans-Dicke引力，Einstein-Aether引力等，检验引力的宇称对称性；引力波标准汽笛和引力波源的空间定位，空间引力波探测器数值模拟及其对哈勃常数和暗能量状态方程的限制、原初引力波的数据分析与模拟方面等方面做出了一系列的研究工作。在项目执行期间，本团队围绕引力波天文学共发表论文24篇，被引用300余次。在读博士生4名，硕士生6名，出站博士后3名，培养博士生2名，本科生4名。完成了项目设定的目标。