Boltzmann brains and the scale-factor cutoff measure of the multiverse
Boltzmann brains and the scale-factor cutoff measure of the multiverse
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玻尔兹曼大脑和多元宇宙的尺度因子截止测量
DOI：
10.1103/physrevd.82.063520
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发表时间：
2008
影响因子：
5
通讯作者：
A. Vilenkin
中科院分区：
文献类型：
--
作者：
A. Simone;A. Guth;Andrei Linde;Mahdiyar Noorbala;Michael P. Salem;A. Vilenkin
为了预测一个永远膨胀的“多重宇宙”，人们必须采用一种调节其发散时空体积的方法。最近，出现了对这种时空测量的新测试：在从热的大爆炸条件冷却下来的口袋宇宙中进化的正常观察者，在数量上不能被“玻尔兹曼大脑”远远超过--由于罕见的量子涨落而突然出现和消失的反常观察者。如果玻尔兹曼大脑占了上风，那么随机选择的观察者极有可能被一个空的世界所包围，在那里，除了真空能量之外，所有的能量都红移了，而不是我们观察到的丰富结构。使用尺度因子截断测量，我们计算玻尔兹曼大脑与正常观察者的比例。我们发现的比例是有限的，并给出一个表达式，它在玻尔兹曼脑成核率和真空衰减率。我们讨论的条件，这些利率必须遵守的比率是可以接受的，我们讨论的各种假设下的利率估计。
To make predictions for an eternally inflating 'multiverse', one must adopt a procedure for regulating its divergent spacetime volume. Recently, a new test of such spacetime measures has emerged: normal observers - who evolve in pocket universes cooling from hot big bang conditions - must not be vastly outnumbered by 'Boltzmann brains' - freak observers that pop in and out of existence as a result of rare quantum fluctuations. If the Boltzmann brains prevail, then a randomly chosen observer would be overwhelmingly likely to be surrounded by an empty world, where all but vacuum energy has redshifted away, rather than the rich structure that we observe. Using the scale-factor cutoff measure, we calculate the ratio of Boltzmann brains to normal observers. We find the ratio to be finite, and give an expression for it in terms of Boltzmann brain nucleation rates and vacuum decay rates. We discuss the conditions that these rates must obey for the ratio to be acceptable, and we discuss estimates of the rates under a variety of assumptions.