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arXiv 1111.3810astro-ph.CO
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曲率子方案中中微子等曲率扰动的未来限制

Future constraints on neutrino isocurvature perturbations in the curvaton scenario

Eleonora Di Valentino, Massimiliano Lattanzi, Gianpiero Mangano, Alessandro Melchiorri, Pasquale D. Serpico

摘要:

在曲率的情况下,残余的等曲率扰动可以在曲率场衰变后的宇宙中微子分量中留下印记,这反过来意味着中微子分布中的化学势不为零。我们研究了未来的实验,如普朗克,SPIDER或CMBPol将能够把中微子分量的等曲率扰动的幅度的限制。我们用非绝热性参数α的平方根γ和超相对论自由度ΔN_eff来表示我们的结果。假设一个具有纯绝热涨落的基准模型,我们发现普朗克(SPIDER)将能够在1 σ水平上设定以下上限:γ<5.3 × 10 ^-3(1.2 × 10 ^-2)和ΔN_eff < 0.16(0.40)。CMBPol将进一步改善这些约束,使γ< 1.5x10^-3,ΔN_eff < 0.043。最后,我们用背景中微子简并度参数σ_n和相应的微扰幅度σ_n重新计算了这些边界,并与大爆炸核合成理论中的σ_n边界进行了比较。

英文摘要:

In the curvaton scenario, residual isocurvature perturbations can be imprinted in the cosmic neutrino component after the decay of the curvaton field, implying in turn a non-zero chemical potential in the neutrino distribution. We study the constraints that future experiments like Planck, SPIDER or CMBPol will be able to put on the amplitude of isocurvature perturbations in the neutrino component. We express our results in terms of the square root γof the non-adiabaticity parameter αand of the extra relativistic degrees of freedom ΔN_eff. Assuming a fiducial model with purely adiabatic fluctuations, we find that Planck (SPIDER) will be able to put the following upper limits at the 1sigma level: γ< 5.3x10^-3 (1.2x10^-2) and ΔN_eff < 0.16 (0.40) . CMBPol will further improve these constraints to γ< 1.5x10^-3 and ΔN_eff < 0.043. Finally, we recast these bounds in terms of the background neutrino degeneracy parameter ξ and the corresponding perturbation amplitude σ_ξ, and compare with the bounds on ξ that can be derived from Big Bang Nucleosynthesis.

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