报告题目：Testing theories of gravity by gravitational wave observations: theories with breaking Lorentz symmetry

报告人：王安忠 教授（美国贝勒大学）

报告时间：2021年9月30日（周四）上午10:00-11:00

报告地点：在线报告（腾讯会议ID：174 439 030）

报告摘要：

So far (September 1, 2021) more than 50 gravitational waves (GWs), emitted by binary systems of black hole - black hole (BBH), or black hole - neutron star (BBN), or neutron star - neutron star (BNS), have been observed by LIGO and Virgo collaborations, since the first detection in the human history by LIGO on September 14, 2015. The 2017 physics Nobel Prize was awarded to three leaders of the observation, Profs. Rainer Weiss, Barry Barish and Kip Thorne, while half of the 2020 physics Nobel Prize went to Prof. Roger Penrose "for the discovery that black hole formation is a robust prediction of the general theory of relativity." Soon, observations of GWs will become routine, and their applications to understanding fundamental physics just start. One of such applications is to test gravitational theories by GW observations.

In this talk, I shall present our recent studies on testing Einstein-aether theory by GWs. Einstein-aether theory is a particular type of the general vector-tensor theory, in which the vector field, the so-called aether, is timelike and unity, so it defines a preferred direction at each given moment and spatial point. As a result, it locally breaks the Lorentz symmetry - a cornerstone of modern physics. Yet, it is self-consistent (free of ghosts, instabilities, and so on), and is consistent with all the observations and experiments. Its Cauchy problem is also well imposed. In addition, due to the presence of the aether, three different species of gravitons exist, the spin-0, spin-1, and spin-2 gravitons, while in Einstein's general theory of relativity (GR), only spin-2 gravitons exist. This will bring dramatical differences especially in the strong-field regime.

I shall first provide a basic overview on GWs in GR, and then report what we have found in Einstein-aether theory. In particular, I shall show that the GW observations already reduce the four free coupling constants of the theory to two, and future studies of GWs emitted in the inspiral and ringdown phases shall further reduce the parameter space of the theory.

参考文献：

[1] S. Tsujikawa, C. Zhang, X. Zhao, A. Wang, Odd-parity stability of black holes in Einstein-Aether gravity, arXiv:2107.08061.

[2] C. Zhang, X. Zhao, K. Lin, S.-J. Zhang, W. Zhao, A. Wang, Spherically symmetric static black holes in Einstein-aether theory, Phys. Rev. D 102, 064043 (2020) [arXiv:2004.06155].

[3] C. Zhang, X. Zhao, A. Wang, B. Wang, K. Yagi, N. Yunes, W. Zhao, T. Zhu, Gravitational waves from the quasi-circular inspiral of compact binaries in Einstein-aether theory, Phys. Rev. D 101, 044002 (2020) [arXiv:1911.10278].

[4] X. Zhao, C. Zhang, K. Lin, T. Liu, R. Niu, B. Wang, S.-J. Zhang, X. Zhang, W. Zhao, T. Zhu, A. Wang, Gravitational waveforms and radiation powers of the triple system PSR J0337+1715 in modified theories of gravity, Phys. Rev. D 100, 083012 (2919) [arXiv:1903.09865].

[5] K. Lin, X. Zhao, C. Zhang, T. Liu, B. Wang, S.-J. Zhang, X. Zhang, W. Zhao, T. Zhu, A. Wang, Gravitational wave forms, polarizations, response functions and energy losses of triple systems in Einstein-Aether theory, Phys. Rev. D 99, 023010 (2019) [arXiv:1810.07707].

[6] J. Oost, S. Mukohyama, A. Wang, Phys. item Constraints on Einstein-aether theory after GW170817, Phys. Rev. D 97, 124023 (2018) [arXiv:1802.04303].

报告人简介：

王安忠教授，籍贯山东聊城，美国贝勒(Baylor)大学教授，引力、宇宙学和天体粒子物理研究中心主任。1983年于山东聊城大学获学士学位，1986年于东北师范大学获硕士学位，1991年于希腊约阿尼纳 (Ioannina)大学获博士学位，1991年至1992年于希腊克里特(Crete)大学从事博士后研究工作，1992年至2003年先后任巴西圣保罗州坎皮纳斯(Campinas)大学副教授、里约热内卢国家天文台副教授、里约热内卢州立大学教授，2003年至今任美国贝勒大学教授。王安忠教授一直在经典及量子引力理论、宇宙学等领域开展研究工作，特别是在黑洞、引力塌缩、引力辐射、暗物质、暗能量、早期宇宙学等领域做了长期系统的研究。在国际学术杂志上发表250余篇学术论文。长期致力于研究生的培养工作, 已指导40余名博士后、博士生及硕士生毕业。现为四个国际学术刊物编委、以及二十几个国际学术刊物、基金会的项目评审专家。

视频链接：

https://www.bilibili.com/video/BV1Su411Z7mH?spm_id_from=333.999.0.0