精确非均匀模型与宇宙介质非对称流引起的光线漂移
Exact inhomogeneous models and the drift of light rays induced by nonsymmetric flow of the cosmic medium
摘要：
在介绍了Szekeres和Lemaitre-Tolman宇宙学模型之后，简要介绍了实时宇宙学程序。然后，指出并纠正了一些关于宇宙学模型的普遍误解。对Szekeres模型中的零测地线方程的研究表明，处于有利位置的观测者将看到星系以每年高达$10^{-6}$角秒的速度在天空中漂移。这种漂移可以使用正在建造的设备进行测量;所需的监测时间为$\approx10$年。这种效应在FLRW模型中为零，因此它提供了宇宙不均匀性的度量。在Szekeres模型中，零漂移的条件是零剪切。但在无剪切正态模型中，零漂移的条件是，在共动坐标中，度量的时间依赖性完全因子化。
英文摘要：
After introducing the Szekeres and Lema\^ıtre--Tolman cosmological models, the real-time cosmology program is briefly mentioned. Then, a few widespread misconceptions about the cosmological models are pointed out and corrected. Investigation of null geodesic equations in the Szekeres models shows that observers in favourable positions would see galaxies drift across the sky at a rate of up to $10^{-6}$ arc seconds per year. Such a drift would be possible to measure using devices that are under construction; the required time of monitoring would be $\approx10$ years. This effect is zero in the FLRW models, so it provides a measure of inhomogeneity of the Universe. In the Szekeres models, the condition for zero drift is zero shear. But in the shearfree normal models, the condition for zero drift is that, in the comoving coordinates, the time dependence of the metric completely factors out.
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