标题： 时间依赖的轴子在辐射和物质主导的宇宙中产生的费米子谱 显示英文标题

标题： Spectra of fermions produced by a time-dependent axion in the radiation- and matter-dominated Universe

摘要： 轴子样自由度通常通过一个平移对称耦合与费米子相互作用。 因此，时间依赖的轴子会导致通过放大其真空涨落而产生费米子。 我们提供了公式，使得可以在具有平坦空间切片的一般弗里德曼-勒梅特-罗伯逊-沃尔克宇宙中确定产生的费米子谱。 然后，我们在产生的费米子对轴子背景的反作用可以忽略的范围内，推导出在辐射主导和物质主导宇宙的具体情况下，产生的费米子谱作为模型参数函数的简单近似公式。 显示英文摘要

摘要： Axion-like degrees of freedom generally interact with fermions through a shift symmetric coupling. As a consequence, a time-dependent axion will lead to the generation of fermions by amplifying their vacuum fluctuations. We provide the formulae that allow one to determine the spectra of produced fermions in a generic Friedmann-Lemaitre-Robertson-Walker Universe with flat spatial slices. Then we derive simple approximate formulae for the spectra of the produced fermions, as a function of the model parameters, in the specific cases of a radiation- and a matter-dominated Universe, in the regime in which the backreaction of the produced fermions on the axionic background can be neglected.