We propose the first model of warm inflation in which the particle production emerges directly from coupling the inflaton to Standard Model particles. Warm inflation, an early epoch of sustained accelerated expansion at finite temperature, is a compelling alternative to cold inflation, with distinct predictions for inflationary observables such as the amplitude of fluctuations, the spectral tilt, the tensor-to-scalar ratio, and non-gaussianities. In our model a heavy QCD axion acts as the warm inflaton whose coupling to Standard Model gluons sources the thermal bath during warm inflation. Axion-like couplings to non-Abelian gauge bosons have been considered before as a successful microphysical theory with emerging thermal friction that can maintain finite temperature during inflation via sphaleron heating. However, the presence of light fermions charged under the non-Abelian group suppresses particle production, hindering a realization of warm inflation by coupling to QCD. We point out that the Standard Model quarks can be heavy during warm inflation if the Higgs field resides in a high-energy second minimum which restores efficient sphaleron heating. A subsequent large reheating temperature is required to allow the Higgs field to relax to its electroweak minimum. Exploring a scenario in which hybrid warm inflation provides the large reheating temperature, we show that future collider and beam dump experiments have discovery potential for a heavy QCD axion taking the role of the warm inflaton.

中文翻译：

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使用重型 QCD 轴子进行热膨胀


我们提出了第一个暖膨胀模型，其中粒子的产生直接来自充气与标准模型粒子的耦合。暖膨胀是在有限温度下持续加速膨胀的早期时期，是冷膨胀的一个引人注目的替代方案，它对膨胀的可观察对象进行了不同的预测，例如波动幅度、光谱倾斜、张量-标量比和非高斯性。在我们的模型中，一个沉重的 QCD 轴子充当暖膨胀子，它与标准模型胶子的耦合在暖充气期间为热浴提供能量。以前曾认为与非阿贝尔规范玻色子的轴状耦合是一种成功的微物理理论，其中出现了热摩擦，可以通过闪子加热在充气过程中保持有限的温度。然而，在非阿贝尔基团下带电的轻费米子的存在抑制了颗粒的产生，阻碍了通过与 QCD 耦合实现暖膨胀。我们指出，如果希格斯场位于高能第二最小值，从而恢复有效的闪长子加热，那么标准模型夸克在暖膨胀期间可能会很重。随后需要一个较大的再加热温度，以使希格斯场松弛到其电弱最小值。探索混合暖膨胀提供大再加热温度的场景，我们表明未来的对撞机和光束转储实验有可能发现重 QCD 轴子取代暖膨胀子的角色。