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arXiv 1003.5892astro-ph.COgr-qchep-phhep-th
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宇宙微波背景圆偏振仪

A circular polarimeter for the Cosmic Microwave Background

Massimo Giovannini

摘要:

观测上并不排除宇宙微波背景的原始圆偏振度。如果等离子体在光子退耦之前被磁化,那么原始二向色性的假设可以被定量地证伪,因为初始的V模偏振影响温度涨落的演化以及线性偏振的方程。温度和偏振角功率谱的观测值被用来推断原始V模式的振幅和光谱斜率上的约束。在光子去耦之前,磁场起到偏振计的作用,因为它们通过将V模式功率谱耦合到剩余的亮度扰动来揭示圆二色性。相反,对于范围在4度和10度之间的角标度,圆偏振幅度和磁场强度的联合边界表明,在0.01 mK范围内对V模式功率谱的直接限制可以直接排除10-100 nG范围内的预去耦磁场。为了本发明的目的,信号的频率依赖性位于GHz范围内。

英文摘要:

A primordial degree of circular polarization of the Cosmic Microwave Background is not observationally excluded. The hypothesis of primordial dichroism can be quantitatively falsified if the plasma is magnetized prior to photon decoupling since the initial V-mode polarization affects the evolution of the temperature fluctuations as well as the equations for the linear polarization. The observed values of the temperature and polarization angular power spectra are used to infer constraints on the amplitude and on the spectral slope of the primordial V-mode. Prior to photon decoupling magnetic fields play the role of polarimeters insofar as they unveil the circular dichroism by coupling the V-mode power spectrum to the remaining brightness perturbations. Conversely, for angular scales ranging between 4 deg and 10 deg the joined bounds on the magnitude of circular polarization and on the magnetic field intensity suggest that direct limits on the V-mode power spectrum in the range of 0.01 mK could directly rule out pre-decoupling magnetic fields in the range of 10-100 nG. The frequency dependence of the signal is located, for the present purposes, in the GHz range.

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