Isocurvature bounds on axions revisited
Isocurvature bounds on axions revisited
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重新审视轴子的等曲率界限
DOI：
10.1103/physrevd.75.103507
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发表时间：
2006
影响因子：
5
通讯作者：
J. Lesgourgues
中科院分区：
文献类型：
--
作者：
M. Beltrán;J. García;J. Lesgourgues
轴子是粒子暗物质最有动力的候选者之一。我们研究并更新了最近的CMB和LSS实验对由失调机制产生的轴子质量的约束，作为暴胀尺度和再加热温度的函数。在一些特殊的（虽然不是非常规的）假设下，轴子会引起等曲率扰动，其振幅太大，无法与观测相一致。具体来说，对于发生在中间能量尺度上的暴胀，我们推导出一些限制性的限制，这些限制只能通过假设一个有效的再加热机制来避免，即${T}_{\ mathm {rh}}g{10}^{11}\text{}\text{}\ mathm {GeV}$。只要Peccei-Quinn尺度${f}_{a}$接近${10}^{10}$或${10}^{11}\text{}\text{}\mathrm{GeV}$，具有二次势的混沌暴胀仍然与轴子场景兼容。等曲率边界消除了较大的${f}_{a}$和较小的不对准角的可能性。我们发现，当暴胀的尺度大于${10}^{12}\text{}\text{}\mathrm{GeV}$时，轴子情景的等曲率约束必须考虑在内；在这个尺度以下，轴子等曲率模态太小，目前的观测无法探测到。
The axion is one of the best motivated candidates for particle dark matter. We study and update the constraints imposed by the recent CMB and LSS experiments on the mass of axions produced by the misalignment mechanism, as a function of both the inflationary scale and the reheating temperature. Under some particular although not unconventional assumptions, the axion induces isocurvature perturbations with an amplitude too large to be compatible with observations. Specifically, for inflation taking place at intermediate energy scales, we derive some restrictive limits which can only be evaded by assuming an efficient reheating mechanism, with ${T}_{\mathrm{rh}}g{10}^{11}\text{ }\text{ }\mathrm{GeV}$. Chaotic inflation with a quadratic potential is still compatible with the axion scenario, provided that the Peccei-Quinn scale ${f}_{a}$ is close to ${10}^{10}$ or ${10}^{11}\text{ }\text{ }\mathrm{GeV}$. Isocurvature bounds eliminate the possibility of a larger ${f}_{a}$ and a small misalignment angle. We find that isocurvature constraints on the axion scenario must be taken into account whenever the scale of inflation is above ${10}^{12}\text{ }\text{ }\mathrm{GeV}$; below this scale, axionic isocurvature modes are too small to be probed by current observations.