论文标题
弯曲空间中的因果关系：光与重力的速度
Causality in Curved Spacetimes: The Speed of Light & Gravity
论文作者
论文摘要
在QED和重力的低能有效场理论中，在弯曲的空间中，低能的光速或引力波的低能速度通常是轻度的。与此相关的是，相对于弯曲背景的少量散射时间可以从已知的光子或重力子的已知有效田间理论系数中出现。我们阐明了为什么这些结果与因果关系，分析性或洛伦兹的不变性不矛盾，并突出了在重力背景下处理超血性和时间进步时出现的各种微妙之处。通过确保在有效理论的有效性制度内计算出的任何时候，一致的低能量有效理论表明可以自我保护，这必然是不可回报的，并且不能说会导致宏观上更大的灯节。这些考虑因素与对宇宙学和引力有效领域理论的约束特别相关，我们提供明确的标准以确保因果关系。
Within the low-energy effective field theories of QED and gravity, the low-energy speed of light or that of gravitational waves can typically be mildly superluminal in curved spacetimes. Related to this, small scattering time advances relative to the curved background can emerge from known effective field theory coefficients for photons or gravitons. We clarify why these results are not in contradiction with causality, analyticity or Lorentz invariance, and highlight various subtleties that arise when dealing with superluminalities and time advances in the gravitational context. Consistent low-energy effective theories are shown to self-protect by ensuring that any time advance and superluminality calculated within the regime of validity of the effective theory is necessarily unresolvable, and cannot be argued to lead to a macroscopically larger lightcone. Such considerations are particularly relevant for putting constraints on cosmological and gravitational effective field theories and we provide explicit criteria to be satisfied so as to ensure causality.
