发表机构
Institute for Basic Science (IBS)（基础科学研究院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文在暴胀背景下非微扰求解自旋-2场与引力子混合的张量系统，发现强混合可指数增强一种螺旋度，产生高度chiral的原初引力波谱，且圆极化度由$\tanh(\pi\theta)$界定。
AI 中文摘要
一个旁观者自旋-2场可以与度规张量微扰线性混合。我们在暴胀背景下研究耦合的张量系统，包括由$\theta$参数化的宇称破缺效应。不对两个场之间的线性混合进行展开，我们在任意质量下精确求解该系统，同时非微扰地处理混合强度。两种螺旋度的模式函数通过将算子值的高斯超几何函数${}_2F_1$作用于Whittaker模式来构造，每个引力子螺旋度的晚期功率谱以广义超几何函数${}_3F_2$的闭式形式表达。我们发现一种螺旋度被指数增强，表明与旁观者自旋-2场的强混合可以产生大且高度chiral的原初引力波谱。圆极化程度由$\tanh(\pi\theta)$界定，与自旋-2质量和混合强度无关。相同的解也给出了旁观者场的晚期功率谱及其与引力子的交叉谱。在弱混合极限下，我们的精确结果重现了微扰Schwinger-Keldysh结果。这些解为研究由额外张量模式产生的原初引力波提供了一个非微扰框架。
英文摘要
A spectator spin-2 field can mix linearly with the metric tensor perturbations. We study the coupled tensor system in an inflationary background, including a parity violating effect parametrised by $θ$. Without expanding in the linear mixing between the two fields, we solve the system exactly for arbitrary mass while treating the mixing strength nonperturbatively. The mode functions of both helicities are constructed by acting with an operator-valued Gauss hypergeometric function ${}_2F_1$ on Whittaker modes, and the late-time power spectrum of each graviton helicity is expressed in closed form in terms of the generalised hypergeometric function ${}_3F_2$. We find that one helicity is exponentially enhanced, showing that strong mixing with a spectator spin-2 field can generate a large and highly chiral primordial gravitational wave spectrum. The degree of circular polarisation is bounded by $\tanh(πθ)$, independently of the spin-2 mass and the mixing strength. The same solution also gives the late-time power spectrum of the spectator field and its cross spectrum with the graviton. In the weak mixing limit, our exact result reproduces the perturbative Schwinger-Keldysh result. These solutions provide a nonperturbative framework for studying primordial gravitational waves sourced by additional tensor modes.
Comments13 pages, 3 figures
