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arXiv 2107.03404gr-qcastro-ph.HEhep-th
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一般超致密天体周围的赤道类时圆轨道

Equatorial timelike circular orbits around generic ultracompact objects

Jorge F. M. Delgado, Carlos A. R. Herdeiro, Eugen Radu

AI总结:

本文证明具有赤道面对称性的超致密天体,其赤道类时圆轨道结构完全由光环的径向稳定性决定,并通过奇异星和非 Kerr 黑洞实例展示了可超过 Kerr 黑洞 42% 最大效率的引力能转化效率。

摘要:

对于稳态、轴对称、渐近平坦且包含光环(LRs)的超致密天体,若其具有固定赤道面的 Z2 南北对称性,我们证明:在赤道光环附近的类时圆轨道(TCOs)结构,无论旋转方向如何,都完全取决于光环的径向稳定性。因此,不稳定光环在其径向上方(下方)界定了一个不稳定 TCOs(无 TCOs)区域;稳定光环在其径向下方(上方)界定了一个稳定 TCOs(无 TCOs)区域。我们讨论了无地平线超致密天体和黑洞的相关推论。我们用多种奇异星例子和非 Kerr 黑洞来展示这些结果,并计算了物质粒子在绝热 TCOs 序列下落时将引力能转化为辐射的效率。对于所研究的大多数天体,可以获得比 Kerr 黑洞最大效率更高的效率,即大于 42%。

英文摘要:

For a stationary, axisymmetric, asymptotically flat, ultra-compact [$i.e.$ containing light-rings (LRs)] object, with a $\mathbb{Z}_2$ north-south symmetry fixing an equatorial plane, we establish that the structure of timelike circular orbits (TCOs) in the vicinity of the equatorial LRs, for either rotation direction, depends exclusively on the radial stability of the LRs. Thus, an unstable LR delimits a region of unstable TCOs (no TCOs) radially above (below) it; a stable LR delimits a region of stable TCOs (no TCOs) radially below (above) it. Corollaries are discussed for both horizonless ultra-compact objects and black holes. We illustrate these results with a variety of exotic stars examples and non-Kerr black holes, for which we also compute the efficiency associated with converting gravitational energy into radiation by a material particle falling under an adiabatic sequence of TCOs. For most objects studied, it is possible to obtain efficiencies larger than the maximal efficiency of Kerr black holes, $i.e.$ larger than $42\%$.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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