非最小耦合暗物质流体宇宙学II. 宇宙学扰动

中文摘要 AI 辅助

我们扩展了对暗物质在流体层面非最小耦合引力的宇宙学情景的研究。在先前工作中，我们展示了这种相互作用可以驱动早期加速膨胀阶段，解决视界和平坦性问题，并且还可以在存在空间曲率的情况下导致宇宙反弹。在这里，我们分析了该框架下线性扰动的演化。我们推导了标量、矢量和张量扰动的控制方程，并在相关宇宙学区域获得了解析解。我们发现，在加速膨胀阶段产生的扰动会产生强烈蓝移的标量功率谱，因此与观测不相容。相比之下，在反弹解中，原初涨落可以在反弹前的收缩阶段起源。在这种情况下，该模型产生近似标度不变的标量功率谱，同时保持张量-标量比与当前界限相容，而无需引入额外的标量场。尽管我们的处理依赖于简化近似，需要在未来工作中加以改进，但这些结果表明非最小耦合暗物质可能为原初宇宙学扰动的产生提供一种可行的替代机制。

英文摘要

We extend our study of a cosmological scenario in which dark matter is non-minimally coupled to gravity at the fluid level. In previous work, we showed that this interaction can drive an early phase of accelerated expansion, addressing the horizon and flatness problems, and can also lead to a cosmological bounce in the presence of negative spatial curvature. Here we analyse the evolution of linear perturbations in this framework. We derive the equations governing scalar, vector and tensor perturbations, and obtain analytic solutions in the relevant cosmological regimes. We find that perturbations generated during the accelerated expansion phase produce a strongly blue scalar power spectrum and are therefore incompatible with observations. By contrast, if primordial fluctuations are generated during the contracting phase of a bouncing solution, the model yields an approximately scale-invariant scalar power spectrum while keeping the tensor-to-scalar ratio compatible with current bounds. Although our treatment relies on simplifying approximations that should be refined in future work, these results indicate that an observationally viable primordial spectrum can be obtained only with a bouncing solution, and hence with a non-singular early-time evolution.

发表机构

• SISSA - International School for Advanced Studies（国际高等研究院）
• INFN, Sezione di Trieste（意大利国家核物理研究所的里雅斯特分部）
• IFPU - Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）
• INAF, IRA - Istituto di Radioastronomia（意大利国家天体物理研究所射电天文学研究所）

机构由 AI 辅助整理，请以论文原文为准。

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备注

29 pages + references, 6 figures. Accepted on JCAP