Reheating is a process where the energy density of a dominant component of the universe other than radiation, such as a matter component, is transferred into radiation. It is usually assumed that the temperature of the universe decreases due to cosmic expansion even during the reheating process, in which case the maximal temperature of the universe is much higher than the reheat temperature. We point out that the temperature of the universe during reheating may in fact increase in well-motivated scenarios. We derive the necessary conditions for the temperature to increase during reheating and discuss concrete examples involving a scalar field. We comment on implications for particle physics and cosmology due to an increasing temperature during reheating.

中文翻译：

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升温至再加热完成

再加热是将宇宙中除辐射以外的主要成分（例如物质成分）的能量密度转换为辐射的过程。通常假设即使在再加热过程中宇宙的温度也会因宇宙膨胀而降低，在这种情况下，宇宙的最高温度远高于再热温度。我们指出，再加热期间宇宙的温度实际上可能会在动机良好的情况下增加。我们推导出再加热期间温度升高的必要条件，并讨论涉及标量场的具体例子。我们评论了重新加热过程中温度升高对粒子物理学和宇宙学的影响。