Non-Gaussianity from curvatons revisited
Non-Gaussianity from curvatons revisited
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DOI：
10.1103/physrevd.84.123506
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发表时间：
2011-07
影响因子：
5
通讯作者：
M. Kawasaki;Takeshi Kobayashi;F. Takahashi
中科院分区：
文献类型：
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作者：
M. Kawasaki;Takeshi Kobayashi;F. Takahashi
我们研究了由具有一般能量势的曲率项引起的密度微扰。偏离二次型的曲率子势的关键特征是，曲率子势经历了一个非均匀的振荡开始。这对由此产生的密度微扰产生了额外的贡献，我们特别发现，非高斯性参数f_nL可以变得很大，具有任何一个符号，无论曲率在宇宙衰变时是支配还是支配宇宙。这种非二次曲率子势是产生红色倾斜密度微扰谱所必需的(而不会引起大场膨胀)，也受到基于微观物理的显式曲率子势的驱动。我们进一步将我们的一般结果应用于曲率是破坏U(1)对称性的伪Nambu-Goldstone(NG)玻色子的情况，并表明所产生的密度微扰朝着能势的山顶区域强烈增强，伴随着非高斯性的轻微增加。这种山顶NG曲率能在大范围的膨胀/再加热尺度下产生观测建议的密度扰动，并进一步预测密度扰动的非高斯性在10<；~f_nl<；~30的范围内。
We investigate density perturbations sourced by a curvaton with a generic energy potential. The key feature of a curvaton potential which deviates from a quadratic is that the curvaton experiences a non-uniform onset of its oscillation. This sources additional contributions to the resulting density perturbations, and we especially find that the non-Gaussianity parameter f_NL can become large with either sign no matter whether the curvaton dominates or subdominates the universe when it decays. Such non-quadratic curvaton potentials are required in order to produce a red-tilted density perturbation spectrum (without invoking large-field inflation), and are also motivated by explicit curvaton models based on microscopic physics. We further apply our generic results to the case where the curvaton is a pseudo-Nambu-Goldstone (NG) boson of a broken U(1) symmetry, and show that the resulting density perturbations are strongly enhanced towards the hilltop region of the energy potential, accompanied by a mild increase of the non-Gaussianity. Such hilltop NG curvatons can produce observationally suggested density perturbations under wide ranges of inflation/reheating scales, and further predict the non-Gaussianity of the density perturbations to lie within the range 10 <~ f_NL <~ 30.