标题： 宇宙学常数及其主导时期 显示英文标题

标题： The cosmological constant and the time of its dominance

摘要： 我们探讨了一个模型，在该模型中，宇宙学常数$\Lambda$和再结合时期密度对比度$\sigma_{rec}$是随机变量，其范围和{\it 先验}概率由物理定律决定。 （此类模型在暴胀宇宙学框架中自然出现。） 基于我们是典型观测者的假设，我们表明三个时间尺度之间的数量级巧合：星系形成的时间、宇宙学常数开始主导宇宙能量密度的时间以及宇宙的当前年龄，可以得到自然的解释。 我们还讨论了$\sigma_{rec}$的概率分布，并发现对于一大类{\it 先验}分布来说，它在观测建议的值附近达到峰值。 显示英文摘要

摘要： We explore a model in which the cosmological constant $\Lambda$ and the density contrast at the time of recombination $\sigma_{rec}$ are random variables, whose range and {\it a priori} probabilities are determined by the laws of physics. (Such models arise naturally in the framework of inflationary cosmology.) Based on the assumption that we are typical observers, we show that the order of magnitude coincidence among the three timescales: the time of galaxy formation, the time when the cosmological constant starts to dominate the cosmic energy density, and the present age of the universe, finds a natural explanation. We also discuss the probability distribution for $\sigma_{rec}$, and find that it is peaked near the observationally suggested values, for a wide class of {\it a priori} distributions.