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arXiv 1202.5370gr-qchep-th
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旋转黑洞背景中的测地流

Geodesic flows in rotating black hole backgrounds

Anirvan DasGupta, Hemwati Nandan, Sayan Kar

摘要:

我们研究了三维(BTZ)和四维(Kerr)旋转黑洞时空几何中类时测地同余的运动学。在这样的时空中的膨胀,剪切和旋转沿测地线流的演变(Raychaudhuri)方程。对于BTZ的情况下,方程解析求解。负宇宙学常数对膨胀演化的影响($θ$),对于有和没有初始旋转的同余($ω_0$)。随后,在四维克尔黑洞的情况下,对某些特定的测地线流的演化方程进行了编写和数值求解。结果表明,对于Kerr黑洞,存在一个初始膨胀的临界值,低于(高于)这个临界值,我们就有聚焦(散焦)。我们描绘的依赖关系的膨胀,对黑洞角动量参数,$a$,以及对$ω_0$。此外,$a$和$ω_0$的作用的时间(仿射参数)的方法的奇异性(散焦/聚焦)进行了研究。虽然$ω_0$在这一时间的作用是预期的,但$a$的作用导致了一个有趣的新结果。

英文摘要:

We study the kinematics of timelike geodesic congruences, in the spacetime geometry of rotating black holes in three (the BTZ) and four (the Kerr) dimensions. The evolution (Raychaudhuri) equations for the expansion, shear and rotation along geodesic flows in such spacetimes are obtained. For the BTZ case, the equations are solved analytically. The effect of the negative cosmological constant on the evolution of the expansion ($θ$), for congruences with and without an initial rotation ($ω_0$) is noted. Subsequently, the evolution equations, in the case of a Kerr black hole in four dimensions are written and solved numerically, for some specific geodesics flows. It turns out that, for the Kerr black hole, there exists a critical value of the initial expansion below (above) which we have focusing (defocusing). We delineate the dependencies of the expansion, on the black hole angular momentum parameter, $a$, as well as on $ω_0$. Further, the role of $a$ and $ω_0$ on the time (affine parameter) of approach to a singularity (defocusing/focusing) is studied. While the role of $ω_0$ on this time of approach is as expected, the effect of $a$ leads to an interesting new result.

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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