Area-minimizing unit vector fields on some spherical annuli
We establish in this paper a sharp lower bound for the area of a unit vector field $V$ defined on some spherical annuli in the Euclidean sphere $\mathbb{S}^2$.
math.DG↗
arXiv subjects
Giovanni Nunes
Publications and source records attributed to Giovanni Nunes.
A correspondence between genus one minimal Lawson surfaces of $\mathbb{S}^3(2)$ and area-minimizing unit vector fields on the antipodally punctured unit 2-sphere
A correspondence is established between a class of minimal immersed surfaces of $\mathbb{S}^3(2)$ and area-minimizing unit vector fields defined on the antipodally punctured unit sphere $\mathbb{S}^2\backslash\{N,S\}$. As a consequence, we establish a stability relation for Lawson cylinders in $\mathbb{S}^3(2)$.
math.DG↗
On the non-parabolicity of $Sol_3$
We prove that $Sol_3$, the isometry group of the Minkowski plane, is non parabolic with respect to any left invariant metric.
math.DG↗
The Dirichlet problem for the minimal hypersurface equation with Lipschitz continuous boundary data on domains of a Riemannian manifold
Given a C2-domain with compact boundary in an arbitrary complete Riemannian manifold, we search for smallness conditions on the boundary data for which the Dirichlet problem for the minimal hypersurface equation is solvable. We obtain an extension to Riemannian manifolds of an existence result of G. H. Williams ( J. Reine Angew. Math. 354:123-140, 1984).
math.DG↗
On the critical points of the energy functional on vector fields of a Riemannian manifold
Given a compact Lie subgroup $G$ of the isometry group of a compact Riemannian manifold $M$ with a Riemannian connection $\nabla,$ it is introduced a $G-$symmetrization process of a vector field of $M$ and it is proved that the critical points of the energy functional \[ F(X):=\frac{\int_{M}\left\Vert \nabla X\right\Vert ^{2}dM}{\int_{M}\left\Vert X\right\Vert ^{2}dM}% \] on the space of $\ G-$invariant vector fields are critical points of $F$ on the space of all vector fields of $M,$ and that this inclusion may be strict in general. One proves that the infimum of $F$ on $\mathbb{S}^{3}$ is not assumed by a $\mathbb{S}^{3}-$invariant vector field. It is proved that the infimum of $F$ on a sphere $\mathbb{S}^{n},$ $n\geq2,$ of radius $1/k,$ is $k^{2},$ and is assumed by a vector field invariant by the isotropy subgroup of the isometry group of $\mathbb{S}^{n}$ at any given point of $\mathbb{S}% ^{n}.$ It is proved that if $G$ is a compact Lie subgroup of the isometry group of a compact rank $1$ symmetric space $M$ which leaves pointwise fixed a totally geodesic submanifold of dimension bigger than or equal to $1$ then all the critical points of $F$ are assumed by a $G-$invariant vector field. Finally, it is obtained a characterization of the spheres by proving that on a certain class of Riemannian compact manifolds $M$ that contains rotationally symmetric manifolds and rank $1$ symmetric spaces$,$ with positive Ricci curvature $\operatorname*{Ric}\nolimits_{M}$, $F$ has the lower bound $\operatorname*{Ric}\nolimits_{M}/\left( n-1\right) $ among the $G-$ invariant vector fields, where $G$ is the isotropy subgroup of the isometry group of $M$ at a point of $M,$ and that his lower bound is attained if and only if $M$ is a sphere of radius $1/\sqrt{\operatorname*{Ric}\nolimits_{M}}.$
math.DG↗