arXiv 1702.021162017-02-07hep-phastro-ph.COgr-qchep-th

超轻暗物质轴子的宇宙学产生

Cosmological production of ultralight dark matter axions

Alberto Diez-Tejedor, David J. E. Marsh

备注：: 13 pages, 3 figures

摘要：

质量为$m_a\sim 10^{-22}\,\textrm{eV}$的标量场的高密度低能激发可以代表宇宙的全部暗物质含量，并缓解小尺度上标准宇宙学场景中的一些紧张局势。这种{ \it模糊暗物质}成分通常被认为是物质扇区中新的类轴子粒子的结果，但为了简单起见，它通常被建模为一个简单的自由二次场。在本文中，我们考虑如何修改宇宙学约束时，瞬子势和温度依赖的质量的影响。目前的等曲率和张量边界证实，这个粒子应该形成之前的低尺度膨胀期与哈勃参数$H_I\lesssim 2.5\times 10^{12}\,\textrm{GeV}$，根据以前的自由场分析结束。轴子衰变常数$f_a$是确定轴子耦合的重要参数，它出现在瞬子势中，决定着遗迹的丰度、星系核对轴子辐射的稳定性以及模糊暗物质的直接搜索。如果轴子质量是$T$独立的，我们发现，$f_a\gtrsim 10^{16}\,\text{GeV}$是必要的，以达到所观察到的遗物密度没有微调的初始条件，而对于一个$T$依赖的情况下，这个界限可以降低一个数量级。然而，瞬子势中的非谐性，主要是一个$T$依赖的质量，可以延迟场振荡的发生，导致更大的物理抑制尺度的物质功率谱为一个固定的零温度轴子质量。这可能有利于一个字符串或意外的轴子出现在一个强耦合规范部门，如果这个模型需要提供大的星系晕核心，同时满足观测约束宇宙结构的形成。

英文摘要：

The highly populated, low-energy excitations of a scalar field of mass $m_a\sim 10^{-22}\,\textrm{eV}$ can represent the full dark matter content of the universe and alleviate some tensions in the standard cosmological scenario on small-scales. This {\it fuzzy dark matter} component is commonly assumed to arise as the consequence of a new axion-like particle in the matter sector, yet for simplicity it is usually modeled in terms of a simple free quadratic field. In this paper we consider how the cosmological constraints are modified when the effects of an instanton potential and temperature-dependent mass are included. Current isocurvature and tensor bounds confirms that this particle should be formed before the end of a low-scale inflation period with Hubble parameter $H_I\lesssim 2.5\times 10^{12}\,\textrm{GeV}$, in accordance with previous free-field analysis. The axion decay constant, $f_a$, which fixes axion couplings, appears in the instanton potential and determines the relic abundance, the stability of galaxy cores to axion emission, and the direct searches of fuzzy dark matter. If the axion mass is $T$-independent, we find that $f_a\gtrsim 10^{16}\,\text{GeV}$ is required in order to reach the observed relic density without fine tuning the initial conditions, while for a $T$-dependent case this bound can be lowered by an order of magnitude. However, the anharmonicities in the instanton potential, and mainly a $T$-dependent mass, can delay the onset of field oscillations, leading to larger physical suppression scales in the matter power spectrum for a fixed zero-temperature axion mass. This may favor a string or accidental axion over one emerging from a strongly coupled gauge sector if this model is required to provide large galactic halo cores while simultaneously satisfying observational constraints from cosmic structure formation.

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。

摘要：

英文摘要：

相关论文