永恒黑洞的辉光
The glow of eternal black holes
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中文总结 AI 辅助
该研究计算被吸积盘环绕的永恒史瓦西黑洞的光学外观，通过替换过去奇点为最后散射面得到中心亮斑，推导其干涉特征，结合M87*和Sgr A*观测约束相关参数，为检验黑洞是否为永恒提供新途径。
中文摘要 AI 辅助
我们计算被几何薄吸积盘环绕的极大扩展（永恒）史瓦西黑洞的光学外观。与引力坍缩形成的天体物理黑洞不同，永恒解包含与过去奇点相连的白洞（WH）区域。根据马尔可夫的物质极限密度假说，我们将过去奇点替换为位于$r=r_{\rm m}$的类空“最后散射面”，并假设该表面发射温度为$T$的黑体辐射。穿过过去视界的逆时光线终止于该表面，从而在永恒黑洞的阴影中心形成一个亮斑。亮斑的径向分布由引力频移决定，当类空表面足够靠近奇点时，中心会出现蓝移。我们使用光线追踪生成吸积盘与亮斑的图像，并推导出亮斑的闭式干涉测量特征。其可见度是基线长度的纯指数函数，与吸积盘和光子环的幂律包络形成对比。我们从M87*和Sgr A*的230 GHz观测通量中约束$r_{\rm m} T$的乘积。我们还考虑普朗克星场景，其中$r_{\rm m}$的值由量纲确定，并表明其超出任何当前或规划中设施的探测范围。不过，观测阴影的黑暗程度仍是检验这些黑洞是否为永恒黑洞的一项测试。
英文摘要
We compute the optical appearance of a maximally extended (eternal) Schwarzschild black hole surrounded by a geometrically thin accretion disk. Unlike astrophysical black holes formed by gravitational collapse, the eternal solution contains a white hole (WH) region connected to a past singularity. Following Markov's hypothesis of a limiting density of matter, we replace the past singularity with a spacelike "surface of last scattering" at $r=r_{\rm m}$ and assume that it emits black-body radiation with temperature $T$. Past-directed rays that cross the past horizon terminate on this surface, resulting in a bright spot at the center of the shadow of an eternal black hole. The radial profile of the spot is set by the gravitational frequency shift, with a blueshifted center when the spacelike surface is sufficiently close to the singularity. We use ray tracing to generate an image of the disk and the spot, and we derive a closed-form interferometric signature of the spot. Its visibility is a pure exponential in the baseline length, in contrast to the power-law envelopes of the disk and the photon ring. We constrain the product $r_{\rm m} T$ from the observed 230 GHz fluxes of M87* and Sgr A*. We also consider a Planck-star scenario in which the value of $r_{\rm m}$ is determined on dimensional grounds, and show that it is out of reach of any current or planned facilities. Nevertheless, the darkness of the observed shadows remains a test of whether these black holes are eternal.
