带质量阿贝尔规范场的轴子暴胀
Axion Inflation with a Massive Abelian Gauge Field
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中文总结 AI 辅助
该研究将暴胀子与无质量阿贝尔规范场耦合的快子放大机制扩展到重质量阿贝尔规范场，通过分析与\texttt{Pencil Code}格点模拟，得到曲率扰动的幂律缩放关系，表明其可满足CMB观测约束。
中文摘要 AI 辅助
暴胀子与阿贝尔规范场之间的轴子耦合可触发一种规范场螺旋度的快子放大。对于无质量矢量，物理动量k/a~|ξ|H的模式会被放大约exp(π|ξ|)，足够高效的产生可为均匀暴胀子提供显著摩擦。我们将该机制扩展到质量为m的矢量，仅当|ξ|>m̄≡m/H时存在不稳定性，在重质量区域，模式振幅按exp[π(|ξ|-m̄)]缩放。由于当m̄≫1时，放大的模式仍远在哈勃半径内，其对长波曲率扰动的贡献在固定背景反作用下呈幂律压低。在弱反作用区域，我们得到P^id_ζ ∝ m̄^-2；计入标量扰动的规范诱导摩擦后，缩放关系为P^id_ζ ∝ m̄^-3。这些估计表明，对于m̄大于数百量级，CMB尺度上P^id_ζ≲10^-9应与规范场反作用兼容。我们基于\texttt{Pencil Code}的重矢量扩展开展首次格点模拟，测试解析模式函数与反作用估计，包括强反作用区域的模拟。
英文摘要
An axial coupling between an inflaton and an Abelian gauge field can trigger the tachyonic amplification of one gauge-field helicity. For a massless vector, modes with physical momentum $k/a\sim |ξ|H$ are enhanced by approximately $\exp(π|ξ|)$, and sufficiently efficient production can provide substantial friction for the homogeneous inflaton. We extend this mechanism to a vector of mass $m$. The instability is present only for $|ξ|>\bar m\equiv m/H$, and in the heavy regime the mode amplitude scales as $\exp[π(|ξ|-\bar m)]$. Because the amplified modes remain well inside the Hubble radius when $\bar m\gg1$, their contribution to long-wavelength curvature perturbations $ζ$ is power-law suppressed at fixed background backreaction. In the weak-backreaction regime we obtain a spectrum ${\cal P}^{\rm id}_ζ \propto \bar m^{-w}$, with $w \sim 2$, while including the gauge-induced friction of scalar perturbations gives the scaling ${\cal P}^{\rm id}_ζ\propto \bar{m}^{-s}$, with $s$ between three and four. These estimates indicate that ${\cal P}^{\rm id}_ζ\lesssim 10^{-9}$ on CMB scales should be compatible with gauge field backreaction for $\bar{m}$ larger than order a few hundred. We test the analytical mode functions and backreaction estimates with the first lattice simulations based on a massive-vector extension of the \texttt{Pencil Code}, including simulations in the strongly backreacting regime.
发表机构
- Universidade do Minho（米尼奥大学）
- Sapienza University of Rome（罗马第一大学）
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