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arXiv 1408.0044gr-qcmath-phmath.MP
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McVittie时空中的粒子和光子轨道

Particle and photon orbits in McVittie spacetimes

Brien C. Nolan

摘要:

麦克维蒂时空代表史瓦西场在各向同性宇宙学背景中的嵌入。根据背景的比例因子,产生的时空可能包含黑洞和白洞视界,以及其他有趣的边界特征。为了进一步阐明这些时空的性质,我们提出了这样一个问题:在McVittie时空中是否存在束缚粒子和光子轨道?考虑到第一个圆形光子轨道,我们得到了一个明确的特征,所有的McVittie时空,这样的轨道存在:有一个2参数类这样的时空,所以圆形光子轨道的存在是一个高度专业化的功能的McVittie时空。然而,我们证明,在两个大类的McVittie时空,有约束粒子和光子轨道:未来完全的非径向类时和零测地线沿面积半径$r$有一个有限的上限。这些测地线在很大程度上渐近于相应史瓦西或史瓦西-德西特时空的圆轨道。这些测地线的存在为在McVittie时空中形成吸积盘奠定了基础,并显示了理论上的可能性。我们还总结和推广了以前关于McVittie时空整体结构的一些结果。利用动力系统理论中的中心流形和其他技巧,建立了关于束缚轨道的结果。

英文摘要:

McVittie spacetimes represent an embedding of the Schwarzschild field in isotropic cosmological backgrounds. Depending on the scale factor of the background, the resulting spacetime may contain black and white hole horizons, as well as other interesting boundary features. In order to further clarify the nature of these spacetimes, we address this question: do there exist bound particle and photon orbits in McVittie spacetimes? Considering first circular photon orbits, we obtain an explicit characterization of all McVittie spacetimes for which such orbits exist: there is a 2-parameter class of such spacetimes, and so the existence of a circular photon orbit is a highly specialised feature of a McVittie spacetime. However, we prove that in two large classes of McVittie spacetimes, there are bound particle and photon orbits: future-complete non-radial timelike and null geodesics along which the areal radius $r$ has a finite upper bound. These geodesics are asymptotic at large times to circular orbits of a corresponding Schwarzschild or Schwarzschild-de Sitter spacetime. The existence of these geodesics lays the foundations for and shows the theoretical possibility of the formation of accretion disks in McVittie spacetimes. We also summarize and extend some previous results on the global structure of McVittie spacetimes. The results on bound orbits are established using centre manifold and other techniques from the theory of dynamical systems.

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