无质量中微子如何影响宇宙微波背景阻尼尾
How Massless Neutrinos Affect the Cosmic Microwave Background Damping Tail
摘要：
我们探讨的物理起源和鲁棒性的约束的能量密度在相对论性的物种之前和重组过程中，通常表示为一个有效的中微子物种，Neff数的约束。威尔金森微波各向异性探测器（WMAP）和南极望远镜（SPT）目前的数据组合的限制几乎完全是由于中微子对膨胀率的影响，以及这些膨胀率的变化如何改变光子扩散尺度与复合时声视界尺度的比值。我们证明，很少的约束力来自早期的集成萨克斯-沃尔夫（ISW）效应，也提供了第一个确定的早期ISW效应的幅度。改变氦中重子质量的分数Yp，也会改变阻尼和声视界尺度的比率。我们讨论的物理效应，防止产生近简并之间的内夫和Yp是一个完整的。检查轻元素丰度的测量，我们没有看到显着的证据演化的Neff和重子-光子比从大爆炸核合成的时代去耦。最后，我们考虑测量的距离，红移关系在低到中等的红移和它们的影响的值Neff。
英文摘要：
We explore the physical origin and robustness of constraints on the energy density in relativistic species prior to and during recombination, often expressed as constraints on an effective number of neutrino species, Neff. Constraints from current data combination of Wilkinson Microwave Anisotropy Probe (WMAP) and South Pole Telescope (SPT) are almost entirely due to the impact of the neutrinos on the expansion rate, and how those changes to the expansion rate alter the ratio of the photon diffusion scale to the sound horizon scale at recombination. We demonstrate that very little of the constraining power comes from the early Integrated Sachs-Wolfe (ISW) effect, and also provide a first determination of the amplitude of the early ISW effect. Varying the fraction of baryonic mass in Helium, Yp, also changes the ratio of damping to sound-horizon scales. We discuss the physical effects that prevent the resulting near-degeneracy between Neff and Yp from being a complete one. Examining light element abundance measurements, we see no significant evidence for evolution of Neff and the baryon-to-photon ratio from the epoch of big bang nucleosynthesis to decoupling. Finally, we consider measurements of the distance-redshift relation at low to intermediate redshifts and their implications for the value of Neff.
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