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arXiv 0810.5591gr-qcastro-phhep-th
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时空离散的能量-动量扩散

Energy-momentum diffusion from spacetime discreteness

Fay Dowker, Lydia Philpott, Rafael Sorkin

摘要:

我们研究了大质量和无质量粒子运动的时空离散性的潜在可观察后果。首先,我们描述了一些简单的内在模型的运动的一个大质量的点粒子在一个固定的因果集的背景。在大尺度下,由原子性引起的微观转向表现为由单个唯象参数控制的能量-动量的洛伦兹不变扩散,我们完全推导出相应的扩散方程。受简单的结果的启发,我们然后推导出最一般的洛伦兹不变扩散方程的无质量粒子,它原来包含两个唯象参数描述,分别扩散和漂移的粒子的能量。然而,粒子并没有离开光锥:它们的世界线仍然是零测地线。最后,我们从宇宙微波背景辐射光谱的黑体性质推导出光子漂移和扩散常数的界。

英文摘要:

We study potentially observable consequences of spatiotemporal discreteness for the motion of massive and massless particles. First we describe some simple intrinsic models for the motion of a massive point particle in a fixed causal set background. At large scales, the microscopic swerves induced by the underlying atomicity manifest themselves as a Lorentz invariant diffusion in energy-momentum governed by a single phenomenological parameter, and we derive in full the corresponding diffusion equation. Inspired by the simplicity of the result, we then derive the most general Lorentz invariant diffusion equation for a massless particle, which turns out to contain two phenomenological parameters describing, respectively, diffusion and drift in the particle's energy. The particles do not leave the light cone however: their worldlines continue to be null geodesics. Finally, we deduce bounds on the drift and diffusion constants for photons from the blackbody nature of the spectrum of the cosmic microwave background radiation.

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