Powell James R, Lopez-Mobilia Rafael, Matzner Richard A
Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX 78249, USA.
Theory Group, University of Texas at Austin, Austin, TX 78712, USA.
Entropy (Basel). 2020 Jul 21;22(7):795. doi: 10.3390/e22070795.
The cosmological singularity of infinite density, temperature, and spacetime curvature is the classical limit of Friedmann's general relativity solutions extrapolated to the origin of the standard model of cosmology. Jacob Bekenstein suggests that thermodynamics excludes the possibility of such a singularity in a 1989 paper. We propose a re-examination of his particle horizon approach in the early radiation-dominated universe and verify it as a feasible alternative to the classical inevitability of the singularity. We argue that this minimum-radius particle horizon determined from Bekenstein's entropy bound, necessarily quantum in nature as a quantum particle horizon (QPH), precludes the singularity, just as quantum mechanics provided the solution for singularities in atomic transitions as radius r → 0 . An initial radius of zero can never be attained quantum mechanically. This avoids the spacetime singularity, supporting Bekenstein's assertion that Friedmann models cannot be extrapolated to the very beginning of the universe but only to a boundary that is 'something like a particle horizon'. The universe may have begun in a bright flash and quantum flux of radiation and particles at a minimum, irreducible quantum particle horizon rather than at the classical mathematical limit and unrealizable state of an infinite singularity.
具有无限密度、温度和时空曲率的宇宙学奇点是弗里德曼广义相对论解外推到宇宙学标准模型起源时的经典极限。雅各布·贝肯斯坦在1989年的一篇论文中提出，热力学排除了这种奇点存在的可能性。我们提议重新审视他在早期辐射主导宇宙中的粒子视界方法，并验证它是奇点经典必然性的一种可行替代方案。我们认为，由贝肯斯坦熵界确定的这个最小半径粒子视界，本质上必然是量子的，即量子粒子视界（QPH），它排除了奇点，就如同量子力学为原子跃迁中半径r→0时的奇点提供了解决方案一样。从量子力学角度永远无法达到初始半径为零的状态。这避免了时空奇点，支持了贝肯斯坦的论断，即弗里德曼模型不能外推到宇宙的起始，而只能外推到一个“类似于粒子视界”的边界。宇宙可能始于一道明亮的闪光以及辐射和粒子的量子通量，起始于一个最小的、不可约的量子粒子视界，而非始于经典数学极限和无限奇点这种无法实现的状态。
