标题： 振荡子与外部标量场的衰减和寿命：从不稳定带分析中获得的见解 显示英文标题

标题： Decay and lifetime of oscillons coupled to an external scalar field: Insights from instability band analysis

摘要： 振子是寿命较长的球对称孤立波，可以在势能比二次势更浅的真实标量场理论中出现。它们被认为是在暴胀后的再加热阶段通过参数共振形成的，并具有较长的寿命。然而，当考虑到暴胀场与其他场之间的相互作用时，对其寿命的估计变得复杂，这在现实的再加热场景中是自然预期的。在本研究中，我们研究了外部真实标量场的耦合如何影响单个振子的寿命。通过数值计算以非均匀振子轮廓为背景的外部场的不稳定性带，我们表明共振行为复杂地依赖于耦合强度和振子的形状。我们分析了在不同耦合强度和振子形状区域占主导地位的不同不稳定性机制。特别是，我们表明当振子尺寸过于有限而无法驱动外部场的增强时，参数共振不会发生。此外，我们的模拟显示，当振子失去能量时，外部场的指数增长可能在振子达到坍缩临界能量之前终止，这表明即使在强耦合或大振幅的情况下，外部场也不一定会导致振子的快速破坏。这些结果表明，振子可以在广泛的耦合强度范围内保持长寿命，这对它们在宇宙演化中的作用具有潜在意义。 显示英文摘要

摘要： Oscillons are long-lived, spherically symmetric solitons that can arise in real scalar field theories with potentials shallower than quadratic ones. They are considered to form via parametric resonance during the preheating stage after inflation and have extended lifetimes. However, the estimation of their lifespan becomes complicated when taking into account the interactions between the inflaton field and other fields, as naturally expected in realistic reheating scenarios. In this study, we investigate how the lifetime of a single oscillon is affected by the coupling to the external real scalar field. By numerically computing the instability bands of the external field with the inhomogeneous oscillon profile as background, we show that the resonance behavior depends intricately on the coupling strength and shape of the oscillon. We analyze distinct instability mechanisms that dominate across different regimes of the coupling strength and oscillon shapes. Especially, we show that the parametric resonance fails to occur when the oscillon size is too limited to drive enhancement of the external field. Furthermore, our simulations show that as the oscillon loses energy, the exponential growth of the external field can terminate before the oscillon reaches its critical energy for collapse, which indicates that the external field does not necessarily lead to rapid destruction of oscillons even in the presence of strong coupling or with large amplitudes. These results suggest that oscillons can remain long-lived across a wide range of coupling strengths, with potential implications for their role in cosmological evolution.