宇宙遗迹丰度与f（R）引力
Cosmic relic abundance and f(R) gravity
摘要：
利用PAMELA（Payload for Antimatter-Matter Exploration and Light-nucleus Astrophysics）实验获得的最新数据，评述了$f(R)$引力的宇宙学后果。这项合作报告了过量的正电子事件，这些事件无法用传统的宇宙学和粒子物理学来解释，通常被归因于暗物质的存在（特别是弱相互作用的大质量粒子）。PAMELA数据的暗物质解释激发了对替代宇宙学模型（相对于标准宇宙学）的研究，因为它们预测哈勃膨胀率的增强，以这种方式产生具有更大遗迹丰度的热遗迹。我们的分析表明，$f(R)$宇宙学允许解释PAMELA之谜的暗物质遗迹粒子的顺序或小于$10^2$ GeV的制度$ρ^c \lesssim ρ^m $，其中$ρ^c$是曲率密度和$ρ^m$辐射密度。对于模型$f(R)=R+αR^n$，则可以得出结论，$n\simeq 1$和相对于广义相对论的小修正确实可以导致解决实验结果。然而，其他有趣的宇宙学模型可以考虑在前BBN时代的BBN约束放松。在这种情况下，PAMELA数据可以适合更大类的$f(R)$模型。
英文摘要：
The cosmological consequences of $f(R)$ gravity are reviewed in the framework of recent data obtained by PAMELA (Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics) experiment. This collaboration has reported an excess of positron events that cannot be explained by conventional cosmology and particle physics, and are usually ascribed to the dark matter presence (in particular, weak interacting massive particles). The dark matter interpretation of PAMELA data has motivated the study of alternative cosmological models (with respect to the standard cosmology) owing to the fact that they predict an enhancement of the Hubble expansion rate, giving rise, in such a way, to thermal relics with a larger relic abundance. Our analysis shows that $f(R)$ cosmology allows to explain the PAMELA puzzle for dark matter relic particles with masses of the order or lesser than $10^2$ GeV in the regime $ρ^c \lesssim ρ^m $ where $ρ^c$ is the curvature density and $ρ^m$ the radiation density. For the model $f(R)=R+αR^n$, it then follows that $n\simeq 1$ and small corrections with respect to General Relativity could lead indeed to address the experimental results. However other interesting cosmological models can be considered during the pre-BBN epoch as soon as the BBN constraints are relaxed. In such a case, the PAMELA data can be fitted for a larger class of $f(R)$-models.
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