Steinhardt Paul J, Turok Neil
Joseph Henry Laboratories, Princeton University, Princeton, NJ 08544, USA.
Science. 2006 May 26;312(5777):1180-3. doi: 10.1126/science.1126231. Epub 2006 May 4.
Within conventional big bang cosmology, it has proven to be very difficult to understand why today's cosmological constant is so small. In this paper, we show that a cyclic model of the universe can naturally incorporate a dynamical mechanism that automatically relaxes the value of the cosmological constant, including contributions to the vacuum density at all energy scales. Because the relaxation time grows exponentially as the vacuum density decreases, nearly every volume of space spends an overwhelming majority of the time at the stage when the cosmological constant is small and positive, as observed today.
在传统的大爆炸宇宙学中，已证明很难理解为何如今的宇宙学常数如此之小。在本文中，我们表明宇宙的循环模型能够自然地纳入一种动力学机制，该机制会自动使宇宙学常数的值弛豫，包括所有能量尺度下对真空密度的贡献。由于弛豫时间会随着真空密度的降低呈指数增长，几乎每一个空间体积在绝大多数时间里都处于宇宙学常数小且为正的阶段，正如如今所观测到的那样。
