Exact solutions for shells collapsing towards a pre-existing black hole

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	Exact solutions for shells collapsing towards a pre-existing black hole
	Liu, Y; Zhang SN(张双南); Zhang, SN
刊名	PHYSICS LETTERS B
	2009
卷号	679 期号:2 页码:#REF!
关键词	Black holes Classical theories of gravity Space-time singularities
通讯作者	Liu, Y (reprint author), Tsinghua Univ, Dept Phys, Beijing 100084, Peoples R China.
英文摘要	The gravitational collapse of a star is an important issue both for general relativity and astrophysics, which is related to the well-known "frozen star" paradox. This paradox has been discussed intensively and seems to have been solved in the comoving-like coordinates. However, to a real astrophysical observer within a finite time, this problem should be discussed in the point of view of the distant rest-observer, which is the main purpose of this Letter. Following the seminal work of Oppenheimer and Snyder (1939), we present the exact solution for one or two dust shells collapsing towards a pre-existing black hole. We find that the metric of the inner region of the shell is time-dependent and the clock inside the shell becomes slower as the shell collapses towards the pre-existing black hole. This means the inner region of the shell is influenced by the property of the shell, which is contrary to the result in Newtonian theory. It does not contradict the Birkhofrs theorem, since in our case we cannot arbitrarily select the clock inside the shell in order to ensure the continuity of the metric. This result in principle may be tested experimentally if a beam of light travels across the shell, which will take a longer time than without the shell. It can be considered as the generalized Shapiro effect, because this effect is due to the mass outside, but not inside as the case of the standard Shapiro effect. We also found that in real astrophysical settings matter can indeed cross a black hole's horizon according to the clock of an external observer and will not accumulate around the event horizon of a black hole, i.e., no "frozen star" is formed for an external observer as matter falls towards a black hole. Therefore, we predict that only gravitational wave radiation can be produced in the final stage of the merging process of two coalescing black holes. Our results also indicate that for the clock of an external observer. matter, after crossing the event horizon, will never arrive at the "singularity" (i.e. the exact center of the black hole), i.e., for all black holes with finite lifetimes their masses are distributed within their event horizons, rather than concentrated at their centers. We also present a worked-out example of the Hawking's area theorem. (C) 2009 Published by Elsevier B.V.
学科主题	Physics
类目[WOS]	Physics, Multidisciplinary
收录类别	SCI
WOS记录号	WOS:000269479800002
公开日期	2016-05-03
内容类型	期刊论文
源URL	[http://ir.ihep.ac.cn/handle/311005/226054]
专题	高能物理研究所_粒子天体物理中心
推荐引用方式 GB/T 7714	Liu, Y,Zhang SN,Zhang, SN. Exact solutions for shells collapsing towards a pre-existing black hole[J]. PHYSICS LETTERS B,2009,679(2):#REF!.
APA	Liu, Y,张双南,&Zhang, SN.(2009).Exact solutions for shells collapsing towards a pre-existing black hole.PHYSICS LETTERS B,679(2),#REF!.
MLA	Liu, Y,et al."Exact solutions for shells collapsing towards a pre-existing black hole".PHYSICS LETTERS B 679.2(2009):#REF!.