CMB power spectra induced by primordial cross-bispectra between metric perturbations and vector fields
CMB power spectra induced by primordial cross-bispectra between metric perturbations and vector fields
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DOI：
10.1088/1475-7516/2012/11/046
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发表时间：
2012-09
影响因子：
6.4
通讯作者：
M. Shiraishi;S. Saga;Shuichiro Yokoyama
中科院分区：
文献类型：
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作者：
M. Shiraishi;S. Saga;Shuichiro Yokoyama
本文研究了由暴胀模型产生的宇宙微波背景辐射的温度和偏振各向异性。如果再加热后矢量场仍然存在，则辐射占优时期由矢量场组成的各向异性应力会增强原初标量和张量涨落。我们表明，通过这种增强的原始交叉双谱产生不仅CMB双谱，但CMB功率谱。一般来说，我们可以预期这种交叉双谱产生标量和张量涨落之间的非平凡模式耦合信号。然而，我们明确表明，这种模式耦合信号不出现在CMB功率谱。通过对CMB标量模功率谱的数值分析，我们发现，虽然这些交叉双谱的信号小于初级非电磁信号，但它们具有一些特征，例如温度和偏振模式的负自相关。另一方面，张量模式的信号几乎可以与初级非电磁模式的信号相比较，因此在非电磁情况下，观测到的B模式谱的形状可能偏离预测。这些印记可能有助于我们判断早期宇宙中标量场和矢量场之间是否存在耦合。
We study temperature and polarization anisotropies of the cosmic microwave background (CMB) radiation sourced from primordial cross-bispectra between metric perturbations and vector fields, which are generated from the inflation model where an inflaton and a vector field are coupled. In case the vector field survives after the reheating, both the primordial scalar and tensor fluctuations can be enhanced by the anisotropic stress composed of the vector fields during radiation dominated era. We show that through this enhancement the primordial cross-bispectra generate not only CMB bispectra but also CMB power spectra. In general, we can expect such cross-bispectra produce the non-trivial mode-coupling signals between the scalar and tensor fluctuations. However, we explicitly show that such mode-coupling signals do not appear in CMB power spectra. Through the numerical analysis of the CMB scalar-mode power spectra, we find that although signals from these cross-bispectra are smaller than primary non-electromagnetic ones, these have some characteristic features such as negative auto-correlations of the temperature and polarization modes, respectively. On the other hand, signals from tensor modes are almost comparable to primary non-electromagnetic ones and hence the shape of observed B-mode spectrum may deviate from the prediction in the non-electromagnetic case. The above imprints may help us to judge the existence of the coupling between the scalar and vector fields in the early Universe.