Isocurvature perturbations in extra radiation
Isocurvature perturbations in extra radiation
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DOI：
10.1088/1475-7516/2012/02/022
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发表时间：
2011-07
影响因子：
6.4
通讯作者：
M. Kawasaki;Koichi Miyamoto;K. Nakayama;Toyokazu Sekiguchi
中科院分区：
文献类型：
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作者：
M. Kawasaki;Koichi Miyamoto;K. Nakayama;Toyokazu Sekiguchi
最近的宇宙学观测，包括CMB各向异性和原始氦丰度的测量，表明在宇宙中存在一种超出标准三种中微子的额外辐射成分。本文探讨了额外辐射具有等曲率涨落的可能性。一个一般的形式主义，以评估额外的辐射等曲率扰动提供了在混合的暴胀-曲率系统，其中额外的辐射是由两个标量场的衰变。我们还推导出额外的辐射和其等曲率扰动量的丰度的约束。目前的观测资料支持额外辐射分量的存在，但并不表明它具有等曲率扰动。这些约束条件被应用到一些粒子物理动机的模型。如果未来的观测在额外辐射中检测到等曲率扰动，它将给我们一个额外辐射起源的提示。
Recent cosmological observations, including measurements of the CMB anisotropy and the primordial helium abundance, indicate the existence of an extra radiation component in the Universe beyond the standard three neutrino species. In this paper we explore the possibility that the extra radiation has isocurvatrue fluctuations. A general formalism to evaluate isocurvature perturbations in the extra radiation is provided in the mixed inflaton-curvaton system, where the extra radiation is produced by the decay of both scalar fields. We also derive constraints on the abundance of the extra radiation and the amount of its isocurvature perturbation. Current observational data favors the existence of an extra radiation component, but does not indicate its having isocurvature perturbation. These constraints are applied to some particle physics motivated models. If future observations detect isocurvature perturbations in the extra radiation, it will give us a hint to the origin of the extra radiation.