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In general relativity, a naked singularity is a gravitational singularity without an event horizon. In a black hole, the singularity is completely enclosed by a boundary known as the event horizon, inside which the gravitational force of the singularity is strong enough so that light cannot escape. Hence, objects inside the event horizon—including the singularity itself—cannot be directly observed. A naked singularity, by contrast, is observable from the outside. The theoretical existence of naked singularities is important because their existence would mean that it would be possible to observe the collapse of an object to ''infinite density''. It would also cause foundational problems for general relativity, because general relativity cannot make predictions about the future evolution of space-time near a singularity. In generic black holes, this is not a problem, as an outside viewer cannot observe the space-time within the event horizon. Some research has suggested that if loop quantum gravity is correct, then naked singularities could exist in nature,〔M. Bojowald, (''Living Rev. Rel.'' 8, (2005), 11 )〕〔R. Goswami & P. Joshi, (''Phys. Rev. D'', (2008) )〕〔R. Goswami, P. Joshi, & P. Singh, (''Phys. Rev. Letters'', (2006), 96 )〕 implying that the cosmic censorship hypothesis does not hold. Numerical calculations〔D. Eardley & L. Smarr, (''Phys. Rev. D.'', (1979), 19 )〕 and some other arguments〔A. Krolak, (''Prog. Theor. Phys. Supp.'', (1999) 136, 45 )〕 have also hinted at this possibility. To date, it has not been possible to observe the presence or absence of black hole event horizons in nature. ==Predicted formation== From concepts drawn of rotating black holes, it is shown that a singularity, spinning rapidly, can become a ring-shaped object. This results in two event horizons, as well as an ergosphere, which draw closer together as the spin of the singularity increases. When the outer and inner event horizons merge, they shrink toward the rotating singularity and eventually expose it to the rest of the universe. A singularity rotating fast enough might be created by the collapse of dust or by a supernova of a fast-spinning star. Studies of pulsars and some computer simulations (Choptuik, 1997) have been performed. This is an example of a mathematical difficulty (divergence to infinity of the density) which reveals a more profound problem in our understanding of the relevant physics involved in the process. A workable theory of quantum gravity should be able to solve problems such as these. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Naked singularity」の詳細全文を読む スポンサード リンク
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