arXiv subjects

Kouji Ogawa

Publications and source records attributed to Kouji Ogawa.

3 recordsLinked to original sources

arXiv2009

Perturbations of Spacetime around a Stationary Rotating Cosmic String

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 frame-dragging around the rotation axis and linear frame-dragging along the rotation axis, the Newtonian logarithmic potential, and the angular deficit around the string as the potential mode. We also investigate gravitational waves propagating off the string and propagating along the string, and show that the stationary rotating string emits gravitational waves toward the directions specified by discrete angles from the rotation axis. Waveforms, polarizations, and amplitudes which depend on the direction are shown explicitly.

gr-qc↗

arXiv2008

Stationary Rotating Strings as Relativistic Particle Mechanics

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 application. These rotating strings have infinite length with various wiggly shapes. Averaged value of the string energy, the angular momentum and the linear momentum along the string are discussed.

gr-qc↗

arXiv2005

Quasinormal Ringing for Acoustic Black Holes at Low Temperature

We investigate a condensed matter ``black hole'' analogue, taking the Gross-Pitaevskii (GP) equation as a starting point. The linearized GP equation corresponds to a wave equation on a black hole background, giving quasinormal modes under some appropriate conditions. We suggest that we can know the detailed characters and corresponding geometrical information about the acoustic black hole by observing quasinormal ringdown waves in the low temperature condensed matters.

gr-qc↗