发表机构
Indian Institute of Technology Guwahati（印度理工学院古瓦哈提分校）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
该研究通过耦合标量场衰变与辐射反作用的动力学方程，数值验证了Starobinsky模型能自然实现暴胀后优雅退出并进入辐射主导阶段，满足再加热成功准则。
AI 中文摘要
Starobinsky模型成功实现了暴胀，并作为替代暴胀模型的基准。受其观测成功的启发，我们研究了该框架内早期宇宙的动力学演化。通过纳入标量场（scalaron）衰变产生的辐射，我们构建了一个耦合动力学方程组，描述标量场的耗散和辐射的累积，同时确保在膨胀背景中能量精确守恒。在Friedmann方程中，标量场和辐射分量均产生引力效应，从而考虑了所产生辐射的反作用。从无辐射宇宙和标准慢滚近似的初始条件出发，精确数值演化表明暴胀动力学主要由标量场主导。尽管持续产生辐射，辐射分量仍保持次主导，且慢滚条件在整个暴胀期间持续成立，产生约60个e-fold。暴胀结束后，标量场进入阻尼振荡阶段，伴随辐射快速增长。这一转变提供了从暴胀优雅退出并平滑进入再加热阶段。在再加热期间，随着标量场能量耗散，辐射持续增长，最终辐射能量密度显著大于残余标量场能量密度。这表明热辐射主导相的开始，满足Kofman-Yi成功再加热准则。我们的结果表明，耦合的标量场-辐射动力学为Starobinsky模型中优雅退出和向辐射主导转变提供了自洽的实现。
英文摘要
The Starobinsky model provides a successful realization of inflation and serves as a benchmark for alternative inflationary models. Motivated by its observational success, we investigate the dynamical evolution of the early Universe within this framework. Incorporating radiation production from scalaron decay, we formulate a coupled system of dynamical equations describing scalaron depletion and radiation buildup while ensuring exact energy conservation in the expanding background. In the Friedmann equation, both scalaron and radiation components gravitate, thereby accounting for the backreaction of the generated radiation. Starting with a radiation-free Universe and initial conditions from the standard slow-roll approximations, exact numerical evolution shows that inflationary dynamics is predominantly governed by the scalaron. Despite continuous radiation production, the radiation component remains subdominant, and the slow-roll conditions persist throughout inflation, yielding approximately 60 e-folds. Following inflation, the scalaron enters a damped oscillatory phase accompanied by rapid radiation growth. This transition provides a graceful exit from inflation and a smooth entry into reheating. During reheating, radiation grows continuously as the scalaron energy is depleted, with the radiation energy density ultimately becoming substantially larger than the residual scalaron energy density. This indicates the onset of a hot, radiation-dominated phase, satisfying the Kofman-Yi criterion for successful reheating. Our results demonstrate that the coupled scalaron-radiation dynamics provides a self-consistent realization of graceful exit and the transition to radiation domination in the Starobinsky model.
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