Chain early dark energy: A Proposal for solving the Hubble tension and explaining today’s dark energy,Physical Review D

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Chain early dark energy: A Proposal for solving the Hubble tension and explaining today’s dark energy
Physical Review D ( IF 4.6 ) Pub Date : 2021-10-20 , DOI: 10.1103/physrevd.104.083533
Katherine Freese _{1,

2,

3} , Martin Wolfgang Winkler _{1,

2}

Affiliation

We propose a new model of early dark energy (EDE) as a possible solution to the Hubble tension in cosmology, the apparent discrepancy between local measurements of the Hubble constant

H_{0} ≃ 74 km s^{- 1} {Mpc}^{- 1}

and

H_{0} ≃ 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 (milli-electron-volt 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.

中文翻译：

链式早期暗能量：解决哈勃张力和解释当今暗能量的建议

我们提出了一种新的早期暗能量 (EDE) 模型作为宇宙学中哈勃张力的可能解决方案，即哈勃常数的局部测量值之间的明显差异

H_{0} ≃ 74 公里 秒^{- 1} {多氯联苯}^{- 1}

和

H_{0} ≃ 67 公里 秒^{- 1} {多氯联苯}^{- 1}

从宇宙微波背景 (CMB) 推断。在链式 EDE 中，宇宙经历了一系列一阶相变，从势能中的高能真空开始，然后通过每一个低能亚稳态最小值的链向下隧穿。与所有 EDE 模型一样，真空能量对宇宙总能量密度的贡献最初可以忽略不计，但达到

～ 10 %

围绕物质辐射相等，在宇宙学数据要求它快速红移之前——至少和辐射一样快。我们确实通过一系列操作获得了这种所需的行为

N

隧道事件，并证明对于

N > 600

相变足够快以允许快速渗透，从而避免 CMB 中的大规模各向异性。我们构建了一个链 EDE 的具体例子，它具有准周期势（倾斜余弦）中的标量场，这在轴子物理学中无处不在，因此具有很强的理论动机。有趣的是，真空之间的能量差异可以大致相当于当今暗能量的大小（毫电子伏级）。因此，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，链式 EDE 的最终结果可以提供暗能量的自然解释。我们讨论了一种可以将标量场停止在所需最小值的简单机制。因此链式EDE提供了用同一个标量场来解释EDE和暗能量的令人兴奋的前景。

更新日期：2021-10-20

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