标题： 原初黑洞在标量场主导的宇宙中的形成 显示英文标题

标题： Primordial Black Hole Formation in a Scalar Field Dominated Universe

摘要： 我们提出了一种数值代码，用于求解包含标量场和完美流体的球对称宇宙模型的Misner-Sharp系统。 虽然该代码能够探索涉及最小耦合标量场和完美流体的一般场景，但我们关注的是标量场主导动力学的区域，特别是在后暴胀标量场主导的场景中，宇宙在持续数个$e$-folds的时间内由快速振荡的标量场支配。 我们分析了在二次和四次势能下PBH形成的阈值，从超视界尺度演化配置。 我们的结果确认，四次势能的行为类似于辐射主导的宇宙，导致PBH形成的阈值接近辐射背景中的已建立值。 相反，在二次情况下，由于波状效应对抗引力坍缩，我们观察到与预期的尘埃行为有显著偏差。 尽管数值限制阻止我们演化广泛的初始条件以确定PBH形成的精确阈值，但我们的发现表明，与纯尘埃情景相比，PBH的形成可能被抑制，从而允许稳定孤子结构的形成。 这项研究强调了在表征PBH形成时，正确考虑振荡标量场中的波动力学的重要性。 显示英文摘要

摘要： We present a numerical code that solves the Misner-Sharp system for a spherically symmetric cosmological model containing both a scalar field and a perfect fluid. While the code is capable of exploring general scenarios involving an minimally coupled scalar field and perfect fluid, we focus on the regime where the scalar field dominates the dynamics, particularly in the post-inflationary scalar field-dominated scenario, where the universe is governed by a rapidly oscillating scalar field for a period lasting a few $e$-folds. We analyse the threshold for PBH formation under quadratic and quartic potentials, evolving configurations from superhorizon scales. Our results confirm that a quartic potential behavior is similar to the radiation-dominated universe, resulting in a PBH formation threshold close to the well-established value in radiation backgrounds. Conversely, in the quadratic case, we observe a significant deviation from the expected dust-like behaviour, due to wave-like effects opposing the gravitational collapse. While numerical limitations prevent us from evolving a wide range of initial conditions to determine a precise threshold for PBH formation, our findings suggest that PBH formation may be suppressed with respect to the pure dust scenario, allowing the formation of stable solitonic structures instead. This study highlights the importance of properly accounting for wave dynamics in oscillating scalar fields when characterising PBH formation.