Exactly solvable strings in the Minkowski spacetime (2009)
Kozaki, Hiroshi, Koike, Tatsuhiko, Ishihara, Hideki
We study the integrability of the equations of motion for the Nambu-Goto strings with a cohomogeneity-one symmetry in the Minkowski spacetime. A cohomogeneity-one string has a world surface which is...
Perturbations of Spacetime around a Stationary Rotating Cosmic String (2008)
Ogawa, Kouji, Ishihara, Hideki, Kozaki, Hiroshi, Nakano, Hiroyuki
We consider the metric perturbations around a stationary rotating Nambu-Goto string in Minkowski spacetime. By solving the linearized Einstein equations, we study the effects of azimuthal...
Perturbations of spacetime around a stationary rotating cosmic string (2008)
Ogawa, Kouji, Ishihara, Hideki, Kozaki, Hiroshi, Nakano, Hiroyuki
Archived in arXiv:0811.2846 v1 Now 18, 2008
Strings in five-dimensional anti-de Sitter space with a symmetry (2008)
Koike, Tatsuhiko, Kozaki, Hiroshi, Ishihara, Hideki
The equation of motion of an extended object in spacetime reduces to an ordinary differential equation in the presence of symmetry. By properly defining of the symmetry with notion of cohomogeneity,...
Stationary Rotating Strings as Relativistic Particle Mechanics (2008)
Ogawa, Kouji, Ishihara, Hideki, Kozaki, Hiroshi, Nakano, Hiroyuki, Saito, Shinya
Stationary rotating strings can be viewed as geodesic motions in appropriate metrics on a two-dimensional space. We obtain all solutions describing stationary rotating strings in flat spacetime as an...
Can inhomogeneties accelerate the cosmic volume expansion? (2006)
Kai, Tomohiro, Kozaki, Hiroshi, Nakao, Ken-ichi, Nambu, Yasusada, Yoo, Chul-Moon
If expanding and contracting regions coexist in the universe, the speed of the cosmic volume expansion can be accelerated. We construct simple inhomogeneous dust-filled universe models in which the...
Yoo, Chul-Moon, Nakao, Ken-ichi, Kozaki, Hiroshi, Takahashi, Ryuichi
The distance-redshift relation determined by means of gravitational waves in the clumpy universe is simulated numerically by taking into account the effects of gravitational lensing. It is assumed...
Classification of Cohomogeneity One Strings (2005)
Ishihara, Hideki, Kozaki, Hiroshi
We define the cohomogeneity one string, string with continuous symmetries, as its world surface is tangent to a Killing vector field of a target space. We classify the Killing vector fields by an...
Volume Expansion of Swiss-Cheese Universe (2002)
Kozaki, Hiroshi, Nakao, Ken-ichi
In order to investigate the effect of inhomogeneities on the volume expansion of the universe, we study modified Swiss-Cheese universe model. Since this model is an exact solution of Einstein...