Chain Early Dark Energy: Solving the Hubble Tension and Explaining Today's Dark Energy
Chain Early Dark Energy: Solving the Hubble Tension and Explaining Today's Dark Energy
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早期暗能量链：解决哈勃张力并解释当今的暗能量
DOI：
10.1103/physrevd.104.083533
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发表时间：
2021
影响因子：
6.4
通讯作者：
M. Winkler
中科院分区：
文献类型：
--
作者：
K. Freese;M. Winkler
我们提出了一个新的早期暗能量模型来解决宇宙学中的哈勃张力，即从宇宙微波背景推断的哈勃常数$H_0\simeq 74$kM，S$^-1}$MPC$^-1}$H_0\simeq 67$kM，S$^-1}$mpc$^-1}的局域测量之间的明显差异。在链EDE中，宇宙经历了一系列的一级相变，从势能的高能真空开始，向下穿过每一个较低能量亚稳态极小值的链。就像在所有的EDE模型中一样，真空能量对宇宙总能量密度的贡献一开始可以忽略不计，但在物质-辐射相等的情况下，在宇宙学数据要求它迅速红移--至少与辐射一样快之前，真空能量对宇宙总能量密度的贡献达到10000美元。我们确实通过一系列$N$隧穿事件获得了所需的行为，并表明对于$N&>600$，相变足够快以允许快速渗流，从而避免了CMB中的大尺度各向异性。我们构造了一个以准周期势(倾斜余弦)中的标量场为特征的链EDE的具体例子，这在轴子物理中是普遍存在的，因此具有很强的理论动机。有趣的是，真空之间的能量差可以大致相当于今天的暗能量(MEV标度)。因此，链EDE的最终结果可以提供对暗能量的自然解释，如果在场达到零(或负)能量之前的最后一步隧穿变得极其缓慢。我们讨论了一种简单的机制，它可以将标量场停止在所需的最小值。因此，链EDE为用同一标量场来解释EDE和暗能量提供了令人兴奋的前景。
We propose a new model of Early Dark Energy (EDE) as a solution to the Hubble tension in cosmology, the apparent discrepancy between local measurements of the Hubble constant $H_0\simeq 74$ km s$^{-1}$ Mpc$^{-1}$ and $H_0\simeq 67$ km s$^{-1}$ Mpc$^{-1}$ inferred from the Cosmic Microwave Background (CMB). In Chain EDE, the Universe undergoes a series of first order phase transitions, starting at a high energy vacuum in a potential, and tunneling down through a chain of every lower energy metastable minima. As in all EDE models, the contribution of the vacuum energy to the total energy density of the universe is initially negligible, but reaches $\sim 10\%$ around matter-radiation equality, before cosmological data require it to redshift away quickly -- at least as fast as radiation. We indeed obtain this required behavior with a series of $N$ tunneling events, and show that for $N>600$ the phase transitions are rapid enough to allow fast percolation and thereby avoid large scale anisotropies in the CMB. We construct a specific example of Chain EDE featuring a scalar field in a quasiperiodic potential (a tilted cosine), which is ubiquitous in axion physics and, therefore, carries strong theoretical motivation. Interestingly, the energy difference between vacua can be roughly the size of today's Dark Energy (meV scale). Therefore, the end result of Chain EDE could provide a natural explanation of Dark Energy, if the tunneling becomes extremely slow in the final step before the field reaches zero (or negative) energy. We discuss a simple mechanism which can stop the scalar field in the desired minimum. Thus Chain EDE offers the exciting prospect to explain EDE and Dark Energy by the same scalar field.