arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2303.07282gr-qc
收藏

Wolfram模型系统的非真空解、引力坍缩和离散奇异性定理

Non-Vacuum Solutions, Gravitational Collapse and Discrete Singularity Theorems in Wolfram Model Systems

Jonathan Gorard

摘要:

著名的雷乔杜里测地线同余方程,以及由此产生的彭罗斯和霍金的奇点定理,产生了一组高度普遍的条件,在这些条件下,时空(或者更一般地说,伪黎曼流形)被认为是测地线不完全的。这是一个非平凡的问题,要问是否存在(以及在多大程度上)等价的一般条件,在这些条件下,人们期望离散时空成为测地线不完全的,以及这些条件与连续统中的条件有何不同。本文建立在以前的工作,其中的共形和协变Z4(CCZ 4)公式的柯西问题的爱因斯坦场方程,约束违反阻尼,被定义在Wolfram模型演化的离散(空间)超图的情况下,真空时空,并继续考虑最小的扩展到非真空的情况下,通过引入一个巨大的标量场分布,定义为球形或轴对称。在适当的假设下,这种标量场分布可以被物理解释为坍缩。(和,在轴对称的情况下,均匀旋转)灰尘,我们能够显示,通过严格的数学分析和显式数值模拟相结合,由此产生的离散时空渐近收敛于非旋转史瓦西黑洞解或最大旋转史瓦西黑洞解(极值)克尔黑洞解。虽然在获得这些初步结果时所使用的假设是非常强有力的,但它们仍然提供了希望,即一个更一般的,也许最终是“彭罗斯式”的奇点定理也可以在离散时空的情况下得到证明。

英文摘要:

The celebrated geodesic congruence equation of Raychaudhuri, together with the resulting singularity theorems of Penrose and Hawking that it enabled, yield a highly general set of conditions under which a spacetime (or, more generically, a pseudo-Riemannian manifold) is expected to become geodesically incomplete. It is a non-trivial question to ask whether (and to what extent) there exist equivalently general conditions under which one expects discrete spacetimes to become geodesically incomplete, and how these conditions might differ from those in the continuum. This article builds upon previous work, in which the conformal and covariant Z4 (CCZ4) formulation of the Cauchy problem for the Einstein field equations, with constraint-violation damping, was defined in terms of Wolfram model evolution over discrete (spatial) hypergraphs for the case of vacuum spacetimes, and proceeds to consider a minimal extension to the non-vacuum case by introducing a massive scalar field distribution, defined in either spherical or axial symmetry. Under appropriate assumptions, this scalar field distribution admits a physical interpretation as a collapsing (and, in the axially-symmetric case, uniformly rotating) dust, and we are able to show, through a combination of rigorous mathematical analysis and explicit numerical simulation, that the resulting discrete spacetimes converge asymptotically to either non-rotating Schwarzschild black hole solutions or maximally-rotating (extremal) Kerr black hole solutions, respectively. Although the assumptions used in obtaining these preliminary results are very strong, they nevertheless offer hope that a more general, perhaps ultimately ``Penrose-like'', singularity theorem may be provable in the discrete spacetime case too.

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。

↑