Unifying Early and Late Dark Energy: Dynamical Requirements and Obstructions
统一早期和晚期暗能量:动力学要求和障碍
William Giarè, Jeremy Sakstein
AI总结 本文研究单个标量场能否同时解释早期暗能量(缓解哈勃张力)和晚期宇宙加速,通过自下而上和自上而下分析,发现需要具有陡-更陡-浅三级斜率势的动力学要求,并对统一模型构建施加严格约束。
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- 41 pages, 9 figures, 1 table
我们研究早期和晚期暗能量是否可能来自同一个标量场。采用自下而上的视角,我们首先确定了任何统一场景必须经历的动力学序列,以解释与哈勃张力的再复合前解决方案相关的早期暗能量阶段以及宇宙的晚期加速。我们推导了标量能量密度和状态方程的相应要求。然后,我们采用互补的自上而下视角,将这些要求转化为对具有追踪类动力学的最小耦合标量场的相空间结构的约束。我们表明,满足所有要求需要一个具有三个不同斜率的势,按陡-更陡-浅的层次排列。在存在与暗物质共形耦合的情况下,这一结论保持不变。这些结果对构建早期和晚期暗能量统一模型的尝试施加了严格限制。我们讨论了对模型构建的启示。
We investigate whether early- and late-time dark energy could arise from a single scalar field. Adopting a bottom-up perspective, we first identify the sequence of dynamical regimes that any unified scenario must traverse to account for both an early dark energy phase relevant for pre-recombination solutions of the Hubble tension and the late-time acceleration of the Universe. We derive the corresponding requirements on the scalar energy density and equation of state. We then adopt a complementary top-down perspective and translate these requirements into constraints on the phase-space structure of minimally coupled scalar fields with tracking-like dynamics. We show that satisfying all requirements necessitates a potential with three distinct slopes, arranged in a steep-steeper-shallow hierarchy. This conclusion remains unchanged in the presence of conformal couplings to dark matter. These results place strong constraints on attempts to construct unified models of early- and late-time dark energy. We discuss implications for model-building.