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Gaussian curvature, mean curvature, sectional curvature, scalar curvature, curvature tensors (Riemann, Ricci, Weyl)

4 votes
0 answers
126 views

Compressing a hypersurface on the sphere

Suppose $M$ is contained in the northern hemisphere $S_+^{n+1}$ and has nonzero principal curvatures everywhere, i.e., has nonzero gaussian curvature everywhere. …
Eduardo Longa's user avatar
4 votes
2 answers
338 views

Positive scalar curvature on the double of a manifold

Let $(M,g)$ be a compact Riemannian manifold with boundary and assume it has positive scalar curvature. Question. … Is it true that $DM$, the double of $M$, admits a metric of positive scalar curvature? …
Eduardo Longa's user avatar
4 votes
1 answer
290 views

Positive scalar curvature on the total space of a circle bundle

Is it known whether the scalar curvature of $(M,\tilde{g})$ can be strictly positive? …
Eduardo Longa's user avatar
3 votes
1 answer
159 views

Special spheres: principal curvatures with different signs

A theorem by Eschenburg states that if $M$ is $\varepsilon$-convex and $N$ has nonnegative sectional curvature, then $M$ is the boundary of a convex body in $N$; in particular, $M$ is diffeomorphic to …
Eduardo Longa's user avatar
5 votes
1 answer
286 views

Manifolds with boundary admitting no closed embedded minimal hypersurface

Suppose $M$ has nonnegative Ricci curvature and the boundary $\partial M$ is strictly mean convex with respect to the inward unit normal. … My question is: what are examples of compact Riemannian $3$-manifolds with nonnegative scalar curvature (but not nonnegative Ricci curvature) and mean convex boundary that don't admit closed embedded minimal …
Eduardo Longa's user avatar
1 vote
0 answers
57 views

Rigidity case of a geometric theorem for $3$-manifolds with boundary

\inf_{\partial M} H^{\partial M} \leq 2 \pi,$$ where $R_M$ is the scalar curvature of $M$ and $H^{\partial M}$ is the mean curvature of $\partial M$. … $\partial \Sigma_0$ has constant geodesic curvature $\inf_{\partial M} H^{\partial M}$ in $\Sigma_0$, does equality hold? …
Eduardo Longa's user avatar
7 votes
2 answers
362 views

Constant Gaussian curvature disks

Is it true that if $D$ is a Riemannian $2$-disk having constant Gaussian curvature equal to $1$ and whose boundary has constant geodesic curvature, then $D$ is isometric to some geodesic ball of the unit …
Eduardo Longa's user avatar
2 votes
1 answer
129 views

Positive scalar curvature on the double of a manifold (assuming mean convexity of the boundary)

Assume it has positive scalar curvature and $\partial M$ is mean convex (positive mean curvature). Question: Is it true that $DM$, the double of $M$, admits a metric of positive scalar curvature? …
Eduardo Longa's user avatar
2 votes
0 answers
101 views

Intersection of minimal and CMC surfaces

Let $(M,g)$ be a complete and oriented Riemannian 3-manifold without boundary. Given $\Sigma_1$ and $\Sigma_2$ closed surfaces embedded in $M$, where the former is minimal and the latter has CMC $H > …
Eduardo Longa's user avatar
5 votes
0 answers
104 views

What normal variational vector fields are allowed for the area to be preserved?

If $\varphi$ is not minimal (the mean curvature $H$ is not identically zero), then for every $f \in C^\infty(\Sigma)$ such that $\int_\Sigma f H \, \mathrm{d} vol_{\varphi^\ast g} = 0$ there exists a proper …
Eduardo Longa's user avatar
8 votes
1 answer
237 views

Separating spheres in $3$-manifolds of positive scalar curvature and mean convex boundary

Li proved a complete topological classification of those compact, connected and orientable $3$-manifolds with boundary which support Riemannian metrics of positive scalar curvature and mean-convex boundary …
Eduardo Longa's user avatar
2 votes
0 answers
107 views

Critical points of the area functional restricted to CMC embeddings

}t} \right\vert_{t=0} \mathcal{A}([f_t], g_t) = - \int_M H_{f} g(X, \nu) \, \mathrm{d}A_{f^\ast g} + \int_M \operatorname{tr}_{f^\ast g}(f^\ast h) \, \mathrm{d}A_{f^\ast g},$$ where $H_f$ is the mean curvature
Eduardo Longa's user avatar
2 votes
0 answers
119 views

How do conformal maps affect curvature?

Let $(\overline{M}^{n+1}, \langle \cdot, \cdot \rangle)$ be a riemannian manifold with riemannian connection $\overline{\nabla}$ and consider $M^n \subset \overline{M}$ an orientable hypersurface with …
Eduardo Longa's user avatar
0 votes
0 answers
123 views

Is every minimal graph smooth?

The following result was taken from the book of Gilbarg-Trudinger: In particular, if the graph is minimal, then $u$ is smooth. Now comes my question: does the same conclusion hold for graphs over dom …
Eduardo Longa's user avatar
5 votes
0 answers
101 views

How is this product of tensors defined?

first eigenvalue of a small geodesic ball in a riemannian manifold”, by Karp and Pinsky, from where I took the following: Here, $\Delta_{-2}$ denotes the usual Laplacian in $\mathbb{R}^n$, $R$ is the curvature
Eduardo Longa's user avatar