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Simon Kristiansson Sebastiano Sonego Marek A. Abramowicz 《General Relativity and Gravitation》1998,30(2):275-288
We present an exhaustive discussion of the embedding diagrams for the optical geometry of the Reissner-Nordström solutions. Whereas in the black hole sector there are no qualitative differences with respect to the Schwarzschild case, the diagrams are considerably different if naked singularities are present. Our treatment is sufficiently general that it can be applied also to any other static spherically symmetric spacetime. 相似文献
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We briefly review some results concerning theproblem of classical singularities in generalrelativity, obtained with the help of the theory ofdifferential spaces. In this theory one studies a givenspace in terms of functional algebras defined on it.Then we present a generalization of this methodconsisting in changing from functional (commutative)algebras to noncommutative algebras. By representingsuch an algebra as a space of operators on a Hilbertspace we study the existence and properties of variouskinds of singular space-times. The results obtainedsuggest that in the noncommutative regime, supposedly reigning in the Planck era, there is nodistinction between singular and non-singular states ofthe universe, and that classical singularities areproduced in the transition process from thenoncommutative geometry to the standard space-timephysics. 相似文献
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《Mathematische Nachrichten》2017,290(17-18):2874-2878
We find a class of minimal hypersurfaces as the zero level set of Pfaffians, resp. determinants of real dimensional antisymmetric matrices. While and are congruent to the quadratic cone resp. Hsiang's cubic invariant in , (special harmonic ‐invariant cones of degree ⩾4) seem to be new. 相似文献
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