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arXiv 2303.13271gr-qcastro-ph.GAastro-ph.HEhep-th
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未来VLBI观测中对爱因斯坦等效原理的检验

A test of Einstein's equivalence principle in future VLBI observations

Joseph P Johnson, Susmita Jana, S. Shankaranarayanan

AI总结:

本研究提出利用未来VLBI观测黑洞图像检验电磁场非最小耦合对爱因斯坦等效原理的违反,计算了光子环大小变化量,并指出天基望远镜有望实现直接探测。

摘要:

我们证明,对超大质量黑洞的甚长基线干涉测量(VLBI)观测将使我们能够检验广义相对论(GR)的基本原理。GR建立在引力的普遍性和爱因斯坦等效原理(EEP)之上,但EEP并非物理学的基本原理,而是一项经验事实。电磁场的非最小耦合(NMC)会违反EEP,且其效应会在强引力场区域显现。因此,对黑洞的VLBI观测为在强引力场区域检验NMC提供了机会。在自旋参数的领头阶近似下,我们明确证明电磁场的NMC会对黑洞图像产生可观测的修正。此外,我们发现光子环的大小变化约为$3 r_H$,对应人马座A*约为30微角秒,M87约为23微角秒。VLBI望远镜预计在不久的将来能达到约5微角秒的分辨率,但要直接探测光子环,M87需要约1微角秒的分辨率,这一分辨率有望由天基事件视界探测器(Event Horizon Explorer)实现。

英文摘要:

We show that very-long-baseline-interferometry (VLBI) observations of supermassive black holes will allow us to test the fundamental principles of General Relativity (GR). GR is based on the universality of gravity and Einstein's equivalence principle (EEP). However, EEP is not a basic principle of physics but an empirical fact. Non-minimal coupling (NMC) of electromagnetic fields violates EEP, and their effects manifest in the strong-gravity regime. Hence, VLBI observations of black holes provide an opportunity to test NMC in the strong-gravity regime. To the leading order in the spin parameter, we explicitly show that the NMC of the electromagnetic field introduces observable modifications to the black hole image. In addition, we find that the size of the photon rings varies by $\sim 3 r_H$, which corresponds to $\sim 30 μas$ for Sagittarius $A^*$ and $\sim 23 μas$ for M87. VLBI telescopes are expected to attain a resolution of $\sim 5 μas$ in the near future. However, direct detection of photon ring will require the resolution of $\sim 1 μas$ for M87, which can potentially be probed by the space-based Event Horizon Explorer.

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