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# Hoop conjecture in five dimensions: Violation of cosmic censorship

Department of Mathematics and Physics, Osaka City University; Department of Mathematics and Physics, Graduate School of Science, Osaka City University, 558-8585, Osaka, Japan; Department of Physics, Gakushuin University, 171-8588, Tokyo, Japan
Physical Review D (Impact Factor: 4.69). 04/2005; DOI: 10.1103/PhysRevD.71.104014
Source: arXiv

ABSTRACT We study the condition of black hole formation in five-dimensional space-time. We analytically solve the constraint equations of five-dimensional Einstein equations for momentarily static and conformally flat initial data of a spheroidal mass. We numer-ically search for an apparent horizon in various initial hypersurfaces and find both necessary and sufficient conditions for the horizon formation in terms of inequalities relating a geometric quantity and a mass defined in an appropriate manner. In the case of infinitely thin spheroid, our results suggest a possibility of naked singularity formation by the spindle gravitational collapse in five-dimensional space-time.

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##### Article: Scalar Bremsstrahlung in Gravity-Mediated Ultrarelativistic Collisions
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ABSTRACT: Classical bremsstrahlung of a massless scalar field $\Phi$ is studied in gravity mediated ultra-relativistic collisions with impact parameter $b$ of two massive point particles in the presence of $d$ non-compact or toroidal extra dimensions. The spectral and angular distribution of the scalar radiation are analyzed, while the total emitted $\Phi-$energy is found to be strongly enhanced by a $d-$dependent power of the Lorentz factor $\gamma$. The direct radiation amplitude from the accelerated particles is shown to interfere destructively (in the first two leading ultra-relativistic orders) with the one due to the $\Phi-\Phi-graviton$ interaction in the frequency regime $\gamma/b\lesssim \omega \lesssim \gamma^2/b$ in all dimensions.
Journal of High Energy Physics 06/2011; 11. · 5.62 Impact Factor
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##### Article: Formation of naked singularities in five-dimensional space-time
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ABSTRACT: We numerically investigate the gravitational collapse of collisionless particles in spheroidal configurations both in four and five-dimensional (5D) space-time. We repeat the simulation performed by Shapiro and Teukolsky (1991) that announced an appearance of a naked singularity, and also find that the similar results in 5D version. That is, in a collapse of a highly prolate spindle, the Kretschmann invariant blows up outside the matter and no apparent horizon forms. We also find that the collapses in 5D proceed rapidly than in 4D, and the critical prolateness for appearance of apparent horizon in 5D is loosened compared to 4D cases. We also show how collapses differ with spatial symmetries comparing 5D evolutions in single-axisymmetry, SO(3), and those in double-axisymmetry, U(1)$\times$U(1).
Physical review D: Particles and fields 02/2011; 83(6).
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##### Article: Apparent Horizons with Nontrivial Topology and the Hyperhoop Conjecture in Six-Dimensional Space-Times
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ABSTRACT: We investigate the validity of the hyperhoop conjecture, which claims to determine a necessary and sufficient condition for the formation of black hole horizons in higher-dimensional space-times. Here we consider momentarily static, conformally flat initial data sets each describing a gravitational field of uniform massive k-sphere sources, for k=1,2, on the five-dimensional Cauchy surface. The numerical result shows the validity of the hyperhoop conjecture for a wide range of model parameters. We also confirm for the first time the existence of an apparent horizon homeomorphism to S**2 x S**2 or S**1 x S**3, which is a higher-dimensional generalization of the black ring.
Physical review D: Particles and fields 02/2012; 85(4).