Hirotaka Kiyohara

activity

20222026

collaborators

4 papers

math.DG2026

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 $2$ -space satisfying the eigenvalue equation $□ N = 2 H^{2} N$ for the d'Alambert operator $□$ and a non-zero co…

math.DG2026

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…

math.DG2023

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…

math.DG2022

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…