arXiv research

We extend the Chern-Heinz inequalities about mean curvature and scalar curvature of graphs of $C^{2}$-functions to leaves of transversally oriented codimension one $C^{2}$-foliations of Riemannian manifolds. That extends partially Salavessa's work on mean curvature of graphs and generalize results of Barbosa-Kenmotsu-O…

Unified estimates for mean curvature in Lorentz-Minkowski space.

Sharp curvature bounds for minimal graphs over unit disk.

Given $(\bar{M},Ω)$ a calibrated Riemannian manifold with a parallel calibration of rank $m$, and $M^m$ an immersed orientable submanifold with parallel mean curvature $H$ we prove that if $\cos θ$ is bounded away from zero, where $θ$ is the $Ω$-angle of $M$, and if $M$ has zero Cheeger constant, then $M$ is minimal. I…

If a graph submanifold $(x,f(x))$ of a Riemannian warped product space $(M^m\times_{e^ψ}N^n,\tilde{g}=g+e^{2ψ}h)$ is immersed with parallel mean curvature $H$, then we obtain a Heinz type estimation of the mean curvature. Namely, on each compact domain $D$ of $M$, $m\|H\|\leq \frac{A_ψ(\partial D)}{V_ψ(D)}$ holds, wher…

Survey Bernstein-type theorems for graphical surfaces in Euclidean and Lorentz-Minkowski spaces.

This is a survey of our work on spacelike graphic submanifolds in pseudo-Riemannian products, namely on Heinz-Chern and Bernstein-Calabi results and on the mean curvature flow, with applications to the homotopy of maps between Riemannian manifolds.

Let $M^n\subset\mathbb R^{n+1}$ be the graph of a $C^2$-real valued function defined in a closed ball of $\mathbb R^n$. In this work, we obtain upper bounds for $\inf_M|H|$ and $\inf_M|R|$, where $H$ and $R$ are, respectively, the mean curvature and the scalar curvature of $M^n$, generalizing estimates given by Heinz i…

In this overview report we generalize Erhard Heinz' curvature estimate for minimal graphs in R^3 to graphs in R^n of prescribed mean curvature. Secondly, we analyse these problems in the frame of the outer differential geometry which leads us to the notions of normal torsion and normal curvature for immersions in R^4.

Using Schauder's theory for linear elliptic partial differential equations in two independent variables and fundamental estimates for univalent mappings due to E. Heinz we establish an upper bound of the Gaussian curvature of two-dimensional minimal surface graphs in R^n. This leads us to a theorem of Bernstein-Liouvil…

The paper examines critical points of solutions to a surface equation in 3D spacelike spaces.

We succeed in writing 2-dimensional conformally invariant non-linear elliptic PDE (harmonic map equation, prescribed mean curvature equations...etc) in divergence form. This divergence free quantities generalize to target manifolds without symmetries the well known conservation laws for harmonic maps into homogeneous s…

Paper estimates Gaussian curvature of minimal graphs in a specific manifold.

We introduce new partial orders on the set $S^+_n$ of positive-definite matrices of dimension $n$ derived from the homogeneous geometry of $S^+_n$ induced by the natural transitive action of the general linear group $GL(n)$. The orders are induced by affine-invariant cone fields, which arise naturally from a local anal…

Heinz Hopf's famous fibrations of the 2n+1-sphere by great circles, the 4n+3-sphere by great 3-spheres, and the 15-sphere by great 7-spheres have a number of interesting properties. Besides providing the first examples of homotopically nontrivial maps from one sphere to another sphere of lower dimension, they all share…

Revisits Weyl's problem on isometric immersions of spheres into 3D manifolds.

Fermat constants fail to fully identify Clairaut constants for certain geodesics on a surface of revolution.

Study proves surfaces with constant curvature are simple shapes.

The paper classifies hypersurfaces in $\mathbb{H}^2 imes\mathbb{H}^2$ with constant curvature.

Study on biconservative hypersurfaces with constant scalar curvature in space forms.

We prove several facts about the Yamabe constant of Riemannian metrics on general noncompact manifolds and about S. Kim's closely related "Yamabe constant at infinity". In particular we show that the Yamabe constant depends continuously on the Riemannian metric with respect to the fine C^2-topology, and that the Yamabe…

Study CR Yamabe constant and CR structures on manifolds.

The paper studies curves of constant-ratio in pseudo-Galilean space.

The Cheeger constant increases under Ricci flow on spheres.

We first define a complex angle between two oriented spacelike planes in 4-dimensional Minkowski space, and then study the constant angle surfaces in that space, i.e. the oriented spacelike surfaces whose tangent planes form a constant complex angle with respect to a fixed spacelike plane. This notion is the natural Lo…

The paper defines new constants for $p$-Laplacian on manifolds.

Study classifies 3D self-shrinkers with constant second form norm.

In 1926 S. Nakajima (= A. Matsumura) showed that any convex body in $\R^3$ with constant width, constant brightness, and boundary of class $C^2$ is a ball. We show that the regularity assumption on the boundary is unnecessary, so that balls are the only convex bodies of constant width and brightness.

Study refines Siegel-Veech constants for abelian differentials.

Curves with constant torsion can be deformed arbitrarily.

New upper bound for Cheeger constant of hyperbolic surfaces.

Simplified proof for Cheeger's isoperimetric constant.

Study on isoparametric and constant-curvature hypersurfaces in Finsler spaces.

This paper mixes constant sum and constant product market makers to improve their features.

Ruled surfaces with Ricci metrics use curves of constant torsion.

Paper proves a Liouville theorem for solitons with constant curvature.

Estimates eigenvalues and spectrum for graph substructures using isocapacitary constants.

The paper classifies and constructs rotational surfaces with constant astigmatism in space forms.

A number of results for C$^2$-smooth surfaces of constant width in Euclidean 3-space ${\mathbb{E}}^3$ are obtained. In particular, an integral inequality for constant width surfaces is established. This is used to prove that the ratio of volume to cubed width of a constant width surface is reduced by shrinking it along…

Study on surfaces in Heisenberg group with constant mean curvature.

Defines structure constants for specific geometric structures on Lie groups.

Salkowski \cite{salkow}, one century ago, introduced a family of curves with constant curvature but non-constant torsion (Salkowski curves) and a family of curves with constant torsion but non-constant curvature (anti-Salkowski curves) in Euclidean 3-space $\e^3$. In this paper, we adapt definition of such curves to ti…

Study constructs closed curves with constant curvature on cylinders and tori.

It is proved that if an AK2-manifold of dimension greater or equal to 6 is of pointwise constant antiholomorphic sectional curvature, then it is a 6-dimensional manifold of constant negative sectional curvature or a Kähler manifold of constant holomorphic sectional curvature.

Every biharmonic Wintgen ideal submanifold in a Riemannian manifold of constant sectional curvature is either minimal or has constant mean curvature.

The study classifies quasi-Einstein manifolds with constant scalar curvature.

Study constant mean curvature surfaces with integrable boundary conditions.

Concrete example of 2-sphere with constant curvature 1 and closed geodesics.