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81.
Yu. M. Loskutov 《Moscow University Physics Bulletin》2009,64(2):103-109
It is shown that the complete system of classical gravitational equations for an isolated centrally symmetric body yields that: (1) in terms of Galilean coordinates all metric coefficients of the Riemannian space induced by the body cannot be equal to zero or infinity anywhere; (2) they, together with the first-order derivatives, should be continuous everywhere. The equations do not contain solutions corresponding to “black holes,” but admit solutions corresponding to objects for which the surface radius (in terms of standard coordinates) is equal to the double mass of matter under this surface. These objects can make the main contribution to the dark matter of the Universe and explain observed effects, such as gravitational microlensing and other effects. Under certain conditions they can become powerful X-ray sources. 相似文献
82.
Giovanni Preti 《Foundations of Physics》2009,39(9):1046-1054
A famous Newtonian argument by Michell and Laplace, regarding the existence of “dark bodies” and dating back to the end of
the 18th century, is able to provide an exact general-relativistic result, namely the exact formula for the Schwarzschild
radius. Since general relativity was formulated more than a century after this argument had been issued, it looks quite surprising that such a correct prediction could have been possible. Far from
being merely a fortuitous coincidence (as one might justifiably be induced to think), this fact can find a reasonable explanation
once the question is approached the other way round, i.e. from the general-relativistic point of view. By reexamining Laplace’s
proof from this point of view, we discuss here the reasons why Michell-Laplace argument can be so “unexpectedly" correct in
its general-relativistic prediction. 相似文献
83.
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85.
Alexis Larranaga 《理论物理通讯》2011,55(1):72-74
We study the entropy of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) charged black hole, originated from the effective action thatemerges in the low-energy of string theory, beyond semiclassical approximations. Applying the properties of exact differentials for three variables to the first law thermodynamics we derive the quantum correctionsto the entropy of the black hole. The leading (logarithmic) and non leading corrections to the area law are obtained. 相似文献
86.
Discussion on the event horizon and quantum ergosphere of dynamic rotating black holes in a tunneling framework 下载免费PDF全文
According to the Parikh--Wilczek tunneling framework, the locations of the local horizons of dynamic rotating black holes can be worked out. The calculations show that the quantum ergosphere of the black hole is identical with the tunneling potential barrier set by particle's tunneling across the relevant horizon. Then, some discussions on the origin of the Hawking radiation will be shown. 相似文献
87.
We demonstrate the possibility of creating a time gap in the slow light based on spectral hole burning in a fourlevel Doppler broadened sodium atomic system. A time gap is also observed between the slow and the fast light in the hole burning region and near the burnt hole region, respectively. A cloaking time gap is attained in microseconds and no distortion is observed in the transmitted pulse. The width of the time gap is observed to vary with the inverse Doppler effect in this system. Our results may provide a way to create multiple time gaps for a temporal cloak. 相似文献
88.
鉴于企业研发组织内部沟通网络对研发组织中高效、低成本地实现技术信息共享的重要性,本文首先介绍了结构洞的测度方法,并对中间中心性方法进行改进;其次分析了某企业研发组织沟通网络的结构洞情况,指出非正式沟通网络和专业沟通网络的相关性;然后通过比较改进的中心度算法、传统的中心度算法与限制度指标的相似性,验证了该算法的有效性;最后提出一种削弱沟通网络中“核心人物”垄断地位的“搭桥”策略。结果发现:改进的中心度算法适用于带权值沟通网络结构洞的测定,验证了该算法加权方法的有效性,并给出通过非正式组织促进技术信息共享的对策 相似文献
89.
Several sets of radially propagating null congruence generators are exploited in order to form 3-dimensional marginally trapped surfaces, referred to as black hole and cosmological apparent horizons in a Ho?ava universe. Based on this method, we deal with the characteristics of the 2-dimensional space-like spheres of symmetry and the peculiarities of having trapping horizons. Moreover, we apply this method in standard expanding and contracting FLRW cosmological models of a Ho?ava universe to investigate the conditions under which the extra parameters of the theory may lead to trapped/anti-trapped surfaces both in the future and in the past. We also include the cases of negative time, referred to as the finite past, and discuss the formation of anti-trapped surfaces inside the cosmological apparent horizons. 相似文献
90.
In this paper, the solid-core fiber designs constructed by omitting one air-hole at the center of square-lattice silica photonic crystals with rectangular shaped air-holes have been investigated theoretically and their characteristics have been compared with those of square ones. Using commercial simulation software, birefringence, dispersion, numerical aperture and confinement loss of the fundamental modes are analyzed. 相似文献