5 papers
Curve theory in with applications to ruled surfaces in
Atsufumi Honda, Jun-ichi Inoguchi, Hirotaka Kiyohara
The Riemannian product of two unit spheres admits several important geometric interpretations. It can be identified both with the complex quadric and with the…
Framed null curves and timelike surfaces via Lorentzian harmonic maps into de-Sitter 2-space
Shintaro Akamine, Hirotaka Kiyohara
We construct a class of Lorentzian harmonic maps into the de-Sitter -space satisfying the eigenvalue equation for the d'Alambert operator and a non-zero co…
Singularities on timelike minimal surfaces in Lorentzian Heisenberg group
Shintaro Akamine, Hirotaka Kiyohara
Timelike minimal surfaces in the three-dimensional Lorentzian Heisenberg group are shown to be constructed from Lorentzian harmonic maps into the de-Sitter two-sphere, and they nat…
Minimal null scrolls in the three-dimensional Heisenberg group
Hirotaka Kiyohara
In the three-dimensional Heisenberg group equipped with a certain left invariant Lorentzian metric, timelike minimal surfaces which have the Abresch-Rosenberg differentials with va…
Timelike minimal surfaces in the three-dimensional Heisenberg group
Hirotaka Kiyohara, Shimpei Kobayashi
Timelike surfaces in the three-dimensional Heisenberg group with left invariant semi-Riemannian metric are studied. In particular, non-vertical timelike minimal surfaces are charac…