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128 views

The smallest dihedral angle of convex polyhedrons

Given a set of points $\{x_{k}\}_{k=0}^{m} \subset \mathbb{R}^n$, is it always possible to find a constant $c=c(m,n)>0$, depending only on the dimension $n$ and the number $m$, such that, after ...
sorrymaker's user avatar
2 votes
1 answer
200 views

Subset in $[0,1]^k$ with positive density

Given a positive constant $0<\gamma<1$, does there exists integer $k_0>0$ such that for any integer $k\geq k_0$ the following holds?: For any $A\subseteq\left[0,1\right]^k$ with the measure ...
tom jerry's user avatar
  • 349
18 votes
1 answer
1k views

Sperner's Lemma implies Tucker's Lemma - simple combinatorial proof

Sperner’s Lemma is often called the "combinatorial analog" of Brouwer’s Fixed Point Theorem, and similarly Tucker’s Lemma is often called the combinatorial analog of Borsuk–Ulam’s Theorem. We can ...
Claus's user avatar
  • 6,917
15 votes
3 answers
1k views

Classification of Platonic solids

My question is very basic: where can I find a complete (and hopefully self-contained) proof of the classification of Platonic solids? In all the references that I found, they use Euler's formula $v-e+...
Valerie's user avatar
  • 955
3 votes
1 answer
737 views

Klein Bottle exception to the Heawood Conjecture [duplicate]

Possible Duplicate: The Klein bottle and the Heawood Conjecture It is well known that the Heawood Conjecture states that the bound for the number of colours which are sufficient to colour a map ...
Samuel Reid's user avatar
  • 1,441