Hirotaka Yoshino

Black hole formation in the grazing collision of high-energy particles

We numerically investigate the formation of D-dimensional black holes in high-energy particle collision with the impact parameter and evaluate the total cross section of the black hole production. We find that the formation of an apparent horizon occurs when the distance between the colliding particles is less than 1.5 times the effective gravitational radius of each particles. Our numerical result indicates that although both the one-dimensional hoop and the (D-3)-dimensional volume corresponding to the typical scale of the system give a fairly good condition for the horizon formation in the higher-dimensional gravity, the (D-3)-dimensional volume provide a better condition to judge the existence of the horizon.

High-energy head-on collisions of particles and the hoop conjecture

We investigate the apparent horizon formation for high-energy head-on collisions of particles in D-dimensional spacetime. The apparent horizons formed before the instant of collision are obtained analytically. We apply the D-dimensional hoop conjecture to these solutions and show that the horizon formation becomes more difficult for larger D.

Lightlike limit of the boosted Kerr black holes in higher-dimensional spacetimes

Deriving the gravitational field of the high-energy objects is an important theme because the black holes might be produced in particle collisions in the brane world scenario. In this paper, we develop a method for boosting the metric of the stationary objects and taking the lightlike limit in higher-dimensional spacetimes, using the Kerr black hole as one example. We analytically construct the metric of lightlike Kerr black holes and find that this method contains no ambiguity in contrast to the four-dimensional case. We discuss the possible implications of our results in the brane world context.

Hoop conjecture for colliding black holes: Non-time-symmetric initial data

The hoop conjecture is well confirmed in momentarily static spaces, but it has not been investigated systematically for the system with relativistic motion. To confirm the hoop conjecture for non-time-symmetric initial data, we consider the initial data of two colliding black holes with momentum and search an apparent horizon that encloses two black holes. In testing the hoop conjecture, we use two definitions of gravitational mass : one is the ADM mass and the other is the quasi-local mass defined by Hawking. Although both definitions of gravitational mass give fairly consistent picture of the hoop conjecture, the hoop conjecture with the Hawking mass can judge the existence of an apparent horizon for wider range of parameters of the initial data compared to the ADM mass.

Uniqueness of static photon surfaces: Perturbative approach

A photon surface

Static black holes with a negative cosmological constant: Deformed horizon and anti-de Sitter boundaries

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Black hole initial data in Gauss-Bonnet gravity: Momentarily static case

is defined as a three-dimensional timelike hypersurface such that any null geodesic initially tangent to

Time evolution of a thin black ring via Hawking radiation

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Electromagnetic radiation due to naked singularity formation in self-similar gravitational collapse

continues to be included in

Black ring formation in particle systems

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