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8 votes
0 answers
175 views

Placing triangles around a central triangle: Optimal Strategy?

This question has gone for a while without an answer on MSE (despite a bounty that came and went) so I am now cross-posting it here, on MO, in the hope that someone may have an idea about how to ...
Benjamin Dickman's user avatar
1 vote
0 answers
114 views

Explicit computation of Čech-cohomology of coherent sheaves on $\mathbb{P}^n_A$

$\newcommand{\proj}[1]{\operatorname{proj}(#1)} \newcommand{\PSP}{\mathbb{P}}$These days I noticed the following result of (constructive) commutative algebra, which I think is probably well known ...
Jürgen Böhm's user avatar
1 vote
0 answers
80 views

Counting Voronoi cells generated by lattice points

I am working on a problem in dynamical systems where I need to count Voronoi cells arising from nearest neighbours to a subset of the lattice. (See the picture below for an example: the shaded region ...
Anthony Quas's user avatar
  • 22.7k
3 votes
1 answer
103 views

Results in computational geometry utilizing doubling dimension of a metric space

According to Wikipedia, However, many results from classical harmonic analysis and computational geometry extend to the setting of metric spaces with doubling measures. My question is: what are some ...
pyridoxal_trigeminus's user avatar
2 votes
0 answers
53 views

Cylinder orientation representation

I'm trying to find an efficient computation and representation for the following problem. Given a cylinder with height $h$ and radius $r$ with a given position $\mathbf{x} = [x, y, z]$ and $N$ number ...
nilsiism's user avatar
5 votes
2 answers
194 views

Fast algorithms for calculating the distance between measures on finite ultrametric spaces

Let $X$ be a finite ultrametric space and $P(X)$ be the space of probability measures on $X$ endowed with the Wasserstein-Kantorovich-Rubinstein metric (briefly WKR-metric) defined by the formula $$\...
Taras Banakh's user avatar
  • 41.1k
26 votes
2 answers
4k views

Why did Robertson and Seymour call their breakthrough result a "red herring"?

One of the major results in graph theory is the graph structure theorem from Robertson and Seymour https://en.wikipedia.org/wiki/Graph_structure_theorem. It gives a deep and fundamental connection ...
GraphX's user avatar
  • 280
4 votes
1 answer
421 views

Implementation of Koebe–Andreev–Thurston circle packing?

The circle packing theorem (Koebe–Andreev–Thurston theorem) claims for a planar graph, we can pack disjoint circles, such that: the circles correspond to vertices and the disks are tangent if the ...
Jake B.'s user avatar
  • 1,445
4 votes
1 answer
203 views

Reference: Packing under translation is in NP

I am looking for a reference for a result that I am aware of. Let me describe the result. Given a polygon $C$ and polygons $p_1,\ldots,p_n$, it can be decided in NP time, if $p_1,\ldots,p_n$ can be ...
Till's user avatar
  • 469
5 votes
0 answers
350 views

Are nearby points in an algebraic curve necessarily connected?

I would like a result of the following form: For every algebraic curve $C$ in $\mathbb{R}\mathbf{P}^{n-1}$, there exists an explicit and easy-to-compute $\epsilon=\epsilon(C)>0$ such that ...
Dustin G. Mixon's user avatar
4 votes
2 answers
385 views

Complexity of Random Delaunay Triangulation in 3D

My question: Is the number of cells in a three-dimensional Poisson-Delaunay triangulation with $n$ vertices $\mathcal O(n)$ with probability one? which is equivalent to the question Is the ...
Dahn's user avatar
  • 141
4 votes
2 answers
424 views

largest diameter of intersection of two balls

Two closed balls with a common radius are positioned so that the centre of either ball is on the boundary of the other. I am interested in the extremal diameter of their intersection, in an arbitrary ...
András Salamon's user avatar
4 votes
2 answers
330 views

How many dihedral angles need to be specified to uniquely specify a triangulated polyhedron?

Suppose you are given a simplicial complex $K$ homeomorphic to the sphere and for each each edge of the complex a label specifying a length of that edge (this gives us a polyhedral metric on $K$). In ...
John's user avatar
  • 185
2 votes
0 answers
111 views

How to compute explicit equations for the Jacobian of a variety over a field [duplicate]

Suppose we start with a projective curve $X$ over a field $K$, given as a closed subvariety of $\mathbb P^n_K$ by some explicit list of equations. I would like to find an explicit representation of ...
Marc's user avatar
  • 374
1 vote
0 answers
97 views

Geometry of a $(d-1)$-dimensional lattice

Let $\mathbf u\in\mathbb Z^d$ be a primitive vector (i.e. $\gcd(u_i)=1$) and let $\Pi_{\mathbf u^\perp}$ be the orthogonal projection perpendicular to $\mathbf u$. I want to understand the geometry of ...
Anthony Quas's user avatar
  • 22.7k

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