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arXiv 2407.07529hep-phastro-ph.CO
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Kaluza-Klein引力子冻结产生与大爆炸核合成

Kaluza-Klein Graviton Freeze-In and Big Bang Nucleosynthesis

Mathieu Gross, Dan Hooper

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12 pages, 6 figures
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AI总结：

本研究针对额外空间维度模型中Kaluza-Klein引力子的产生与衰变过程，计算其对大爆炸核合成轻元素丰度的影响，给出不同额外维度数下引力基本标度与宇宙最高温度的约束，限制了早期宇宙热浴中黑洞高效产生的可能。

摘要：

在具有额外空间维度的模型中，早期宇宙中的粒子碰撞会产生Kaluza-Klein引力子。这类粒子随后会发生衰变，可能对大爆炸核合成过程产生影响。本文中，我们研究了引力可在n个平直紧致化额外维度中自由传播、而标准模型（Standard Model）场被限制在3+1维膜上的场景。我们计算了构成Kaluza-Klein引力子塔的各态的产生率与衰变率，并确定了其丰度在早期宇宙中的演化过程。随后，我们进一步评估了这些衰变对最终轻元素丰度的影响。我们识别出此前未被探索的参数空间中，与原初氦和氘丰度测量结果不一致的显著区域。具体而言，我们发现对于1个额外维度（2个额外维度）的情况，引力基本标度必须满足M⋆ > 2×10¹³ GeV（M⋆ > 10¹⁰ GeV），除非早期宇宙的温度从未超过T ~ 2 TeV（T ~ 1 GeV）。对于更大的n值，这些约束会相对宽松。例如，在n=6的情况下，我们的分析排除了所有小于~10⁶ GeV的M⋆取值，除非宇宙温度从未超过T ~ 3 TeV。本文给出的结果极大限制了早期宇宙热浴中粒子碰撞高效产生黑洞的可能性。

英文摘要：

In models featuring extra spatial dimensions, particle collisions in the early universe can produce Kaluza-Klein gravitons. Such particles will later decay, potentially impacting the process of Big Bang nucleosynthesis. In this paper, we consider scenarios in which gravity is free to propagate throughout $n$ flat, compactified extra dimensions, while the fields of the Standard Model are confined to a 3+1 dimensional brane. We calculate the production and decay rates of the states that make up the Kaluza-Klein graviton tower and determine the evolution of their abundances in the early universe. We then go on to evaluate the impact of these decays on the resulting light element abundances. We identify significant regions of previously unexplored parameter space that are inconsistent with measurements of the primordial helium and deuterium abundances. In particular, we find that for the case of one extra dimension (two extra dimensions), the fundamental scale of gravity must be $M_{\star} > 2 \times 10^{13} \, {\rm GeV}$ ($M_{\star} > 10^{10} \, {\rm GeV}$) unless the temperature of the early universe was never greater than $T \sim 2 \, {\rm TeV}$ ($T \sim 1 \, {\rm GeV}$). For larger values of $n$, these constraints are less stringent. For the case of $n=6$, for example, our analysis excludes all values of $M_{\star}$ less than $\sim 10^{6} \, {\rm GeV}$, unless the temperature of the universe was never greater than $T \sim 3 \, {\rm TeV}$. The results presented here severely limit the possibility that black holes were efficiently produced through particle collisions in the early universe's thermal bath.

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