动力学反作用无法抑制轴子量子压力
Kinetic backreaction cannot suppress axion quantum pressure
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中文总结 AI 辅助
研究动力学耦合超轻轴子暗物质的反作用，通过解析分析和数值模拟证明，该反作用无法缩小金斯长度以增强结构形成，反而会增大金斯长度，无法实现预期的结构增长效果。
中文摘要 AI 辅助
来自弦紧化的超轻轴子带有非正则动能项，其归一化由依赖于伴随模场的耦合函数决定。作为暗物质，这类轴子会形成冷凝聚体，其量子压力会在由该耦合函数确定的金斯尺度以下抵抗引力坍缩。人们可能期望，凝聚体振荡产生的反作用能够缩小金斯长度，从而增强结构形成。我们证明这无法实现：对于任意光滑正耦合函数，振荡平均后的反作用总会使耦合函数值增大，进而增强量子压力并使金斯长度随时间增长。我们通过绝热不变量分析解析地确立这一不可能结果，并通过直接数值积分予以验证。因此，动力学耦合暗物质无法自产生增强引力坍缩的条件，也无法在亚金斯尺度上触发结构形成。
英文摘要
Ultralight axions from string compactifications carry non-canonical kinetic terms whose normalization is set by a coupling function that depends on an accompanying modulus field. As dark matter, such an axion forms a cold condensate whose quantum pressure resists gravitational collapse below a Jeans scale fixed by that coupling. One might hope that backreaction from the condensate's oscillations could shrink this Jeans length and thereby enhance structure growth. We show that it cannot. For any smooth, positive coupling function, the oscillation-averaged backreaction always drives the coupling to larger values, strengthening the quantum pressure and growing the Jeans length with time. We establish this no-go result analytically through an adiabatic- invariant analysis and confirm it by direct numerical integration. Kinetically coupled dark matter therefore cannot self-generate the conditions for enhanced gravitational collapse or the seeding of structure on sub-Jeans scales.
