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arXiv 0912.3248astro-ph.COhep-phhep-th
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大尺度磁场、暗能量与QCD

Large-Scale Magnetic Fields, Dark Energy and QCD

Federico R. Urban, Ariel R. Zhitnitsky

备注：
jhep style, 22 pages, v2 with updated estimates and extended discussion on parity violation, v3 as published (references updated)
发表信息：
Phys.Rev.D82:043524,2010
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摘要：

宇宙磁场的观测关联长度不断增加，可能达到超星系团的大小，因此不利于传统的图片通过原始种子产生后，由星系约束发电机机制放大。在这篇论文中，我们提出了一种根本不同的方法，将这种大尺度磁场与宇宙真空能量联系起来。在我们的方案中，暗能量是由于Veneziano鬼（它解决了QCD中的$U(1)_A$问题）。Veneziano鬼通过三角形异常耦合到具有在标准模型中明确固定的常数的电磁场。虽然这种相互作用在闵可夫斯基空间中不会产生任何物理效应，但它会在每个时期触发膨胀宇宙中磁场的产生。因此，磁场的感应能量与宇宙学真空能量成正比：$ρ_{EM}\simeq B^2 \simeq (\fracα{4π})^2 ρ_{DE}$，$ρ_{DE}$因此充当磁能$ρ_{EM}$的来源。相应的数值估计导致nG范围内的幅度。我们的建议有两个独特的和与众不同的预测：一个不间断的积极产生哈勃大小的相关磁场在整个宇宙的演化;奇偶性违反巨大的尺度$1/H$，这显然已经在CMB中观察到的存在。这些预言完全植根于粒子物理学的标准模型。

英文摘要：

Cosmological magnetic fields are being observed with ever increasing correlation lengths, possibly reaching the size of superclusters, therefore disfavouring the conventional picture of generation through primordial seeds later amplified by galaxy-bound dynamo mechanisms. In this paper we put forward a fundamentally different approach that links such large-scale magnetic fields to the cosmological vacuum energy. In our scenario the dark energy is due to the Veneziano ghost (which solves the $U(1)_A$ problem in QCD). The Veneziano ghost couples through the triangle anomaly to the electromagnetic field with a constant which is unambiguously fixed in the standard model. While this interaction does not produce any physical effects in Minkowski space, it triggers the generation of a magnetic field in an expanding universe at every epoch. The induced energy of the magnetic field is thus proportional to cosmological vacuum energy: $ρ_{EM}\simeq B^2 \simeq (\fracα{4π})^2 ρ_{DE}$, $ρ_{DE}$ hence acting as a source for the magnetic energy $ρ_{EM}$. The corresponding numerical estimate leads to a magnitude in the nG range. There are two unique and distinctive predictions of our proposal: an uninterrupted active generation of Hubble size correlated magnetic fields throughout the evolution of the universe; the presence of parity violation on the enormous scales $1/H$, which apparently has been already observed in CMB. These predictions are entirely rooted into the standard model of particle physics.

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