近日，美国塔夫茨大学Alexander Cassem团队报道了统一性、因果关系和太阳系边界可能会极大地限制引力波用于检验广义相对论的使用。相关论文于2025年11月24日发表在《高能物理杂志》上。
通过研究合并黑洞产生的引力波（GWs）来探测/约束对广义相对论的偏离，是LIGO/Virgo等引力波干涉仪的主要驱动力之一。在纯引力理论框架下，偏离的唯一可能来源是有效作用量中存在高阶导数修正项，即黎曼曲率张量的更高次幂项。任何观测约束都会对应限制这些修正项的威尔逊系数（Wilson coefficients）。在作用量层面，可以设想这些系数足够大，原则上可被探测。然而，从因果律和幺正性等基本原理出发，这一可能性则远不明确。
研究组对此展开分析，他们首先回顾了这些系数已知的一些约束，这些约束共同表明该有效理论存在低能截断。随后，考虑了一种可能的生成此类修正项的机制，即通过大量仅与引力最小耦合的标量场，这些标量场被积掉（integrated out）后会产生高阶算符。研究组证明，这一过程的副产物是牛顿势的量子修正，而其可观测效应已被太阳系实验排除。他们指出，为避免此类太阳系约束，需要引力波干涉仪的灵敏度提升超过7个数量级。研究组还提到了来自黑洞霍金辐射的额外约束。
附：英文原文
Title: Unitarity, causality, and solar system bounds may significantly limit the use of gravitational waves to test general relativity
Author: Cassem, Alexander, Hertzberg, Mark P.
Issue&Volume: 2025-11-24
Abstract: The prospect of detecting/constraining deviations from general relativity by studying gravitational waves (GWs) from merging black holes has been one of the primary motivations of GW interferometers like LIGO/Virgo. Within pure gravity, the only possible way deviations can arise is from the existence of higher order derivative corrections, namely higher powers of the Riemann curvature tensor, in the effective action. Any observational bounds imply constraints on the corresponding Wilson coefficients. At the level of the action, one can imagine the coefficients are sufficiently large so as to be in principle detectable. However, from the point of view of some fundamental principles, namely causality and unitarity, this is much less clear, as we examine here. We begin by reviewing certain known bounds on these coefficients, which together imply a low cut off on the effective theory. We then consider a possible mechanism to generate such terms, namely in the form of many scalars, minimally coupled to only gravity, that can be integrated out to give these higher order operators. We show that a by product of this is the generation of quantum corrections to Newton’s potential, whose observable consequences are already ruled out by solar system tests. We point out that over 7 orders of magnitude of improvement in interferometer sensitivity would be required to avoid such solar system constraints. We also mention further constraints from Hawking radiation from black holes.
DOI: 10.1007/JHEP11(2025)144
Source: https://link.springer.com/article/10.1007/JHEP11(2025)144