User:Tokenzero/sandbox

User:Jorge_Stolfi/DoW Wall Street Journal: Wikipedia loosing Volunteers

Lemma. For any two elements a and b (st. ab=ba), of order i and j, there is an element of order lcm(i,j). Proof: We can assume $$i \bot j$$, since otherwise we can replace a with an element of order $$i/\text{lcd}(i,j)$$, namely $$a^{\text{lcd}(i,j)}$$. Consider ord(ab)=k. k divides ij. a^k=(b^{-1})^k where b^{-1} has also order j. ord(a^k) divides i = ord(b^k) = divides j, so a^k=b^k=1. So i divides k and j divides k.


 * Degeneracy (graph theory) (e.g. O(d)-time adjacency structure).
 * De_Bruijn_graph, Line graph
 * non-trivial "densest subgraph" algorithms, see non-dynamic refs in Near-Optimal Fully Dynamic Densest Subgraph
 * Wikipedia_talk:WikiProject_Mathematics/Typography
 * max-width
 * PageRank


 * fokonolona (maybe also Balinese 'seka')


 * Modern approaches to early Islamic history – The New Cambridge History of Islam