This investigation delves into the ringdown signals produced by semiclassical stars, which are ultra-compact, regular solutions of the Einstein equations incorporating stress-energy contributions from quantum vacuum polarization. These stars exhibit an approximately Schwarzschild exterior and an interior composed of a constant-density classical fluid and a cloud of vacuum polarization. By adjusting their compactness and density, we can alter the internal structure of these stars without modifying the exterior. This adaptability enables us to examine the sensitivity of the ringdown signal to the innermost regions of the emitting object and to compare it with similar geometries that differ substantially only at the core. Our results indicate that echo signals are intrinsically linked to the presence of stable light rings and can be very sensitive to the internal structure of the emitting object. This point was previously overlooked, either due to the imposition of reflective boundary conditions at the stellar surface or due to the assumption of low curvature interior geometries. Specifically, for stellar-sized semiclassical stars, we find that the interior travel time is sufficiently prolonged to render the echoes effectively unobservable. These findings underscore the potential efficacy of ultra-compact objects as black hole mimickers and emphasize that any phenomenological constraints on such objects necessitate a detailed understanding of their specific properties and core structure.

中文翻译：

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来自量子核心的低语：半经典恒星的环状


这项研究深入研究了半经典恒星产生的振铃信号，这些信号是爱因斯坦方程的超紧凑、规则解，结合了量子真空极化的应力-能量贡献。这些恒星表现出近似史瓦西的外部和由恒定密度经典流体和真空极化云组成的内部。通过调整它们的致密性和密度，我们可以在不改变外部的情况下改变这些恒星的内部结构。这种适应性使我们能够检查振铃信号对发射物体最内层区域的灵敏度，并将其与仅在核心处存在实质性差异的类似几何形状进行比较。我们的结果表明，回波信号与稳定光环的存在有着内在的联系，并且对发射物体的内部结构非常敏感。这一点以前被忽视了，要么是由于在恒星表面施加了反射边界条件，要么是由于假设了低曲率内部几何结构。具体来说，对于恒星大小的半经典恒星，我们发现内部传播时间足够长，以至于回波实际上无法观测。这些发现强调了超紧凑物体作为黑洞模拟物的潜在功效，并强调对此类物体的任何现象学限制都需要详细了解它们的具体特性和核心结构。