185 research outputs found
Hoop Conjecture and Black Holes on a Brane
The initial data of gravity for a cylindrical matter distribution confined to
a brane are studied in the framework of the single-brane Randall-Sundrum
scenario. In this scenario, the 5-dimensional nature of gravity appears in the
short-range gravitational interaction. We find that a sufficiently thin
configuration of matter leads to the formation of a marginal surface, even if
the configuration is infinitely long. This implies that the hoop conjecture
proposed by Thorne does not hold on the brane: Even if a mass does not
become compacted into a region whose circumference in every
direction satisfies , black holes with horizons can form in
the Randall-Sundrum scenario.Comment: 7 pages, 1 figure, To be published in Progress of Theoretical Physics
Supplement No. 148 "Brane World: New Perspective in Cosmology
Two-point correlation function of density perturbations in a large void universe
We study the two-point correlation function of density perturbations in a
spherically symmetric void universe model which does not employ the Copernican
principle. First we solve perturbation equations in the inhomogeneous universe
model and obtain density fluctuations by using a method of non-linear
perturbation theory which was adopted in our previous paper. From the obtained
solutions, we calculate the two-point correlation function and show that it has
a local anisotropy at the off-center position differently from those in
homogeneous and isotropic universes. This anisotropy is caused by the tidal
force in the off-center region of the spherical void. Since no tidal force
exists in homogeneous and isotropic universes, we may test the inhomogeneous
universe by observing statistical distortion of the two-point galaxy
correlation function.Comment: 16 pages, 3 figure
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