We find that the Kerr-(Newman)-${\mathrm{AdS}}_4$ black hole will be shadowless if its rotation parameter is larger than a critical value and shadowless-ness may be related to the appearance of the null hypersurface caustics (NHC) both inside the Cauchy horizon and outside the event horizon for the black hole with the rotation parameter beyond the critical value. Our studies also further confirm that whether an ultraspinning black hole is superentropic or not is unrelated to the existence of the NHC outside the event horizon.

中文翻译：

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无影快速旋转但不超旋 Kerr-AdS4 和 Kerr-Newman-AdS4 黑洞

我们发现 Kerr-(Newman)-${\mathrm{广告服务}}_4$如果黑洞的旋转参数大于临界值，那么黑洞将是无影的，无影性可能与柯西视界内和事件视界外的零超曲面焦散（NHC）的出现有关。参数超出临界值。我们的研究还进一步证实，超旋黑洞是否是超熵与事件视界外 NHC 的存在无关。