We present the first renormalizable quantum field theory model for inflation with a super-Hubble inflaton mass and sub-Planckian field excursions, which is thus technically natural and consistent with a high-energy completion within a theory of quantum gravity. This is done in the framework of warm inflation, where we show, for the first time, that strong dissipation can fully sustain a slow-roll trajectory with slow-roll parameters larger than unity in a way that is both theoretically and observationally consistent. The inflaton field corresponds to the relative phase between two complex scalar fields that collectively break a U(1) gauge symmetry, and dissipates its energy into scalar degrees of freedom in the warm cosmic heat bath. A discrete interchange symmetry protects the inflaton mass from large thermal corrections. We further show that the dissipation coefficient decreases with temperature in certain parametric regimes, which prevents a large growth of thermal inflaton fluctuations. We find, in particular, a very good agreement with the Planck legacy data for a simple quadratic inflaton potential, predicting a low tensor-to-scalar ratio $r\lesssim 10^{-5}$.

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走向可靠的有效膨胀场理论

我们提出了第一个具有超哈勃暴胀子质量和亚普朗克场偏移的可重整化量子场论模型，因此这在技术上是自然的，并且与量子引力理论中的高能完成是一致的。这是在暖暴胀的框架内完成的，我们第一次表明，强耗散可以完全维持慢滚轨迹，慢滚参数大于 1，在理论上和观察上都是一致的。暴胀子场对应于两个复杂的标量场之间的相对相位，它们共同打破了 U(1) 规范对称性，并将其能量耗散到温暖的宇宙热浴中的标量自由度中。离散的交换对称性保护暴胀子质量免受大的热校正。我们进一步表明，在某些参数状态下，耗散系数随温度降低，从而防止了热暴涨波动的大幅增长。我们发现，特别是，对于简单的二次膨胀子势，我们发现与普朗克遗留数据非常吻合，预测低张量与标量比 $r\lesssim 10^{-5}$。