arXiv 2103.018322021-03-02astro-ph.COgr-qchep-ph

不均匀的大爆炸核合成会产生今天不均匀的元素分布吗？

Does inhomogeneous big bang nucleosynthesis produce an inhomogeneous element distribution today?

Robert J. Scherrer

备注：: 5 pages, no figures
发表信息：: Phys. Rev. D 103, 123548 (2021)
DOI：: 10.1103/PhysRevD.103.123548

摘要：

非均匀大爆炸核合成（BBN）在$T \sim 10^9$ K下产生空间非均匀分布的元素丰度，但随后的元素扩散将趋于消除这些非均匀性。我们计算了BBN元素的宇宙学共动扩散长度。这个扩散长度受到原子散射的限制，因此当原子是中性的时，在复合和再电离的红移之间，扩散占主导地位。我们发现，今天的共动扩散长度是$d_{com} \approx 70$ pc的所有感兴趣的元素，除了$^7$锂，其中$d_{com}$是一个数量级较小，因为$^7$锂保持电离在整个相关的时代。这个共动扩散长度对应于一个亚恒星重子质量尺度，大致等于视界尺度在BBN。这些结果支持的可能性，即在BBN的地平线上的尺度大于不均匀性可能会导致今天的空间不均匀分布的元素，而纯粹的亚地平线波动在BBN只能导致在一个均匀的元素分布目前。

英文摘要：

Inhomogeneous big bang nucleosynthesis (BBN) produces a spatially inhomogeneous distribution of element abundances at $T \sim 10^9$ K, but subsequent element diffusion will tend to erase these inhomogeneities. We calculate the cosmological comoving diffusion length for the BBN elements. This diffusion length is limited by atomic scattering and is therefore dominated by diffusion when the atoms are neutral, between the redshifts of recombination and reionization. We find that the comoving diffusion length today is $d_{com} \approx 70$ pc for all of the elements of interest except $^7$Li, for which $d_{com}$ is an order of magnitude smaller because $^7$Li remains ionized throughout the relevant epoch. This comoving diffusion length corresponds to a substellar baryonic mass scale and is roughly equal to the horizon scale at BBN. These results lend support to the possibility that inhomogeneities on scales larger than the horizon at BBN could lead to a spatially inhomogeneous distribution of elements today, while purely subhorizon fluctuations at BBN can result only in a homogeneous element distribution at present.

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