arXiv subjects

Riku Kishida

Publications and source records attributed to Riku Kishida.

3 recordsLinked to original sources

arXiv2026

A new framework of zero mean curvature surfaces in the isotropic 3-space

We introduce a class of zero mean curvature surfaces with singularities in the isotropic 3-space, called ZMC-faces. As a main result, we establish three Osserman-type inequalities for a ZMC-face under certain assumptions on both completeness and finiteness of the total curvature. The equality conditions of these inequalities are related to the asymptotic behaviors of the ends. Moreover, we present several examples of ZMC-faces attaining equalities in these inequalities.

math.DG↗

arXiv2025

The volume of marginally trapped submanifolds in a Lorentzian manifold satisfying the null energy condition

In this paper, we focus on a marginally trapped submanifold $f:\Sigma^n\to M^{n+2}_1$ in a Lorentzian manifold $M^{n+2}_1$. We show that $f$ lies in a certain null hypersurface $\mathcal{N}_f^{n+1}$ in $M^{n+2}_1$ and $f$ has a locally volume-maximizing property in $\mathcal{N}^{n+1}_f$ if $M^{n+2}_1$ satisfies the null energy condition.

math.DG↗

arXiv2024

The volume of conformally flat manifolds as hypersurfaces in the light-cone

In this paper, we focus on a conformally flat Riemannian manifold $(M^n,g)$ of dimension $n$ isometrically immersed into the $(n+1)$-dimensional light-cone $\Lambda^{n+1}$ as a hypersurface. We compute the first and the second variational formulas on the volume of such hypersurfaces. Such a hypersurface $M^n$ is not only immersed in $\Lambda^{n+1}$ but also isometrically realized as a hypersurface of a certain null hypersurface $N^{n+1}$ in the Minkowski spacetime, which is different from $\Lambda^{n+1}$. Moreover, $M^n$ has a volume-maximizing property in $N^{n+1}$.

math.DG↗