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1 vote
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Integral hull of a polyhedron Q is polyhedron

Let $Q \subseteq R^n$ be a rational polyhedron and let $Q_I=Convexhull(Q \cap Z^n)$. By finite basis theorem, we have $Q=P+C$ for some rational polytope $P$ and finitely generated cone $C$ where $C=R_+...
Sowbarnika R's user avatar
4 votes
0 answers
46 views

Implementation of Friedman's algorithm of reconstructing simple polytopes

In Finding a Simple Polytope from Its Graph in Polynomial Time, Friedman gave a polynomial time algorithm on reconstructing a simple polytope from its graph. Has this algorithm been actually ...
mashedcarrots's user avatar
0 votes
1 answer
81 views

Can convex combinations of indicator functions for pairwise non-disjoint sets unordered by inclusion dominate one another?

Let $N$ be a finite subset of the naturals. Let $P$ be a set of subsets of $N$ such that: 1) $P\neq \varnothing$, 2) $\forall x\in P, |x| >1$, 3) $\forall x,y\in P,$ if $x\neq y$, then $x\not\...
VMfoobar's user avatar
16 votes
3 answers
1k views

Can a convex polytope with $f$ facets have more than $f$ facets when projected into $\mathbb{R}^2$?

Let $P$ be a convex polytope in $\mathbb{R}^d$ with $n$ vertices and $f$ facets. Let $\text{Proj}(P)$ denote the projection of $P$ into $\mathbb{R}^2$. Can $\text{Proj}(P)$ have more than $f$ facets? ...
Pedro Ruiz's user avatar
1 vote
1 answer
219 views

approximate diameter of polytopes in high dimensions

I just came across the following problem: Let us consider the unit corner of the n-cube $$ \Delta^n = \left\{(t_1,\cdots,t_n)\in\mathbb{R}^n\mid\sum_{i = 1}^{n}{t_i} \leq 1 \mbox{ and } t_i \ge 0 \...
rjm's user avatar
  • 75
7 votes
1 answer
224 views

A polytope with a bound on the sum of any $k$ variables

Let $2\le k\le n-1$ and define the polytope $$P_k(n) = \lbrace (x_1,\ldots,x_n) \in \mathbb{R}^n : -1\le x_{i_1}+\cdots +x_{i_k} \le 1 \text{ for all } 1\le i_1\lt\cdots\lt i_k\le n\rbrace.$$ There ...
Brendan McKay's user avatar