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arXiv 2104.05352astro-ph.COgr-qc
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宇宙成分的早期热化?解决宇宙张力的一个提示

Early-time thermalization of cosmic components? A hint for solving cosmic tensions

Hermano Velten, Ingrid Costa, Winfried Zimdahl

摘要:

我们研究了一个非相对论性暗物质和辐射在一定时间内相互作用并建立近似热平衡的膨胀双流体模型。这种在背景水平上产生有效体积粘性压力的相互作用预计与从辐射到物质主导的过渡有关。我们量化了在物质辐射相等时期周围$1 {\rm eV} \lesssim m_χ \lesssim 10 {\rm eV}$范围内的暗物质粒子质量的压力大小(即,红移$z_{\rm eq}\sim 3400$),并证明了瞬态体积粘度的存在具有可能与解决标准宇宙学模型的当前张力相关的后果:(一)附加(负)压力贡献修改了$z_{\rm eq}$附近的膨胀率,产生较大的$H_0$值,和ii)大-尺度结构的形成是通过抑制物质过密度增长的幅度,通过一个新的粘性摩擦项贡献的Mészáros效应的影响。结果,当前标准宇宙学模型的$H_0$和$S_8$张力都得到了显著的缓解。

英文摘要:

We study an expanding two-fluid model of non-relativistic dark matter and radiation which are allowed to interact during a certain time span and to establish an approximate thermal equilibrium. Such interaction which generates an effective bulk viscous pressure at background level is expected to be relevant for times around the transition from radiation to matter dominance. We quantify the magnitude of this pressure for dark matter particles masses within the range $1 {\rm eV} \lesssim m_χ \lesssim 10 {\rm eV}$ around the matter-radiation equality epoch (i.e., redshift $z_{\rm eq}\sim 3400$) and demonstrate that the existence of a transient bulk viscosity has consequences which may be relevant for addressing current tensions of the standard cosmological model: i) the additional (negative) pressure contribution modifies the expansion rate around $z_{\rm eq}$, yielding a larger $H_0$ value and ii) large-scale structure formation is impacted by suppressing the amplitude of matter overdensity growth via a new viscous friction-term contribution to the Mészáros effect. As a result, both the $H_0$ and the $S_8$ tensions of the current standard cosmological model are significantly alleviated.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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