Tagged Questions

5
votes
1answer
150 views

Reference request: affine transforms + circle inversion?

This problem cropped up in the context of scale-insensitive methods for generating random variables. Let $X=R^n \cup \{\infty\}$. Suppose we consider a set of transforms $\cal{T} …
3
votes
2answers
169 views

Is there a contractible bounded homogeneous space?

Let us phrase the question in the title in more detail: I wonder if there exists a metric space $X$ which has at least two points, has finite diameter (in the sense that there is a …
4
votes
0answers
55 views

Hilbert metric and cross-ratio of points on simplices

Background and motivation: Consider the cone $C\subset \mathbb{R}^d$ of vectors with non-negative components, and let $\Delta\subset C$ be the simplex of probability vectors (thos …
3
votes
1answer
66 views

Simplex with edges of length at least s having smallest circumradius

Is it true that of all $n$-simplices with edge lengths greater than or equal to some parameter $s$, the regular simplex with edge lengths $s$ has the smallest circumradius? It seem …
0
votes
1answer
131 views

The pth power of a distance function is twice continuously differentiable, for $p>2$?

Suppose $\mathcal{O}$ is an open convex connected strict subset in $\mathbb{R}^n$ and define $\beta(x)=dist(x, \mathcal{O})$, for each $x\in\mathbb{R}^n$. Is $\beta^p$, $p>2$ a tw …
0
votes
2answers
158 views

Higher dimensional convex hull

Let $CH(S)$ be a convex hull of a finite set $S$ and denote the set of all the vertices of $CH(S)$ as $Vert(S)$. For a vertex $v \in Vert(S)$, it has an associated set $E(v)$ which …
2
votes
2answers
437 views

A characterization of Hilbert spaces?

My question was prompted by an earlier MO by @Daniel:     Duality map in strictly convex Banach spaces I will even use his symbol $\phi$ below. Let $B$ be an arbitrary …
1
vote
1answer
107 views

the tangent cone at infinity of manifolds with Rc\geq 0

Is the following statement true? Assume that $(M^n, g, p)$ is a pointed complete manifold with metric $g$, $Rc(g)\geq 0$, ${s_i}$ is a positive sequence decreasing to $0$, and $(M …
3
votes
0answers
87 views

Is every connected metrizable locally path connected space a length space?

Does every connected metrizable locally path connected topological space X admit a compatible metric d so that (X,d) is a length space? (Recall the metric space (X,d) is a length …
7
votes
0answers
117 views

Optimal inspection path on a sphere

Suppose you would like to "inspect" every point of a unit-radius sphere $S \subset \mathbb{R}^3$ by walking along a path $\gamma$ on $S$, but you can only see a distance $d$ from w …
5
votes
1answer
207 views

For what spaces is the Hardy-Littlewood maximal operator of strong type $(p,p)$ if and only if $p > p_0 > 1$?

(This is essentially a continuation of my previous question, here.) Let $(X,d,\mu)$ be a metric measure space, i.e. $\mu$ is a Borel measure on the metric space $(X,d)$. Further a …
6
votes
0answers
81 views

Maximum number of Vertices of Hypercube covered by Ball of radius R

Let $R>0$ be given and let $H^n$ be the unit hypercube in $\mathbb{R}^n$. The problem I am facing is to find the maximum number of vertices of $H^n$ which can be covered by a close …
10
votes
2answers
166 views

Random rings linked into one component?

Let $S$ be a sphere of unit radius. Let $C_n$ be a collection of unit-radius circles/rings whose centers are (uniformly distributed) random points in $S$, and which are oriented (t …
0
votes
0answers
80 views

Optimal paintbrush geodesics

Let $S$ be a smooth, closed surface in $\mathbb{R}^3$, and $\gamma$ a geodesic segment on $S$, i.e., a finite-length piece of a geodesic. Define $\gamma(w)$ as all the points of $S …
17
votes
4answers
681 views

Surfaces filled densely by a geodesic

Which smooth, closed surfaces $S \subset \mathbb{R}^3$ have no single geodesic $\gamma$ that fills $S$ densely? Say a geodesic $\gamma$ "fills $S$ densely" if the closure of …

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