标题： 量子引力扩散与光速的随机涨落 显示英文标题

标题： Quantum-Gravitational Diffusion and Stochastic Fluctuations in the Velocity of Light

摘要： 我们认为时空背景中的量子引力涨落赋予真空非平凡的光学性质，其中包括扩散以及光子到达时间的相应不确定性，从而导致“真空中”光速的随机涨落。 我们的提议是在量子引力的刘维尔弦表述框架下提出的，该表述还暗示了粒子真空具有频率依赖性的折射率。 我们通过研究光子在时空泡沫中$D$- 膜涨落的量子激发下的传播，构建了一个明确的实现方法。 这些涨落由高亏格弦效应描述，导致耦合强度以及光速的随机涨落。 我们讨论了通过遥远天体物理源的$\gamma$- 射线观测来限制或测量“真空中”光子扩散的可能性。 显示英文摘要

摘要： We argue that quantum-gravitational fluctuations in the space-time background give the vacuum non-trivial optical properties that include diffusion and consequent uncertainties in the arrival times of photons, causing stochastic fluctuations in the velocity of light ``in vacuo''. Our proposal is motivated within a Liouville string formulation of quantum gravity that also suggests a frequency-dependent refractive index of the particle vacuum. We construct an explicit realization by treating photon propagation through quantum excitations of $D$-brane fluctuations in the space-time foam. These are described by higher-genus string effects, that lead to stochastic fluctuations in couplings, and hence in the velocity of light. We discuss the possibilities of constraining or measuring photon diffusion ``in vacuo'' via $\gamma$-ray observations of distant astrophysical sources.