Problems / combinatorics
combinatorics / Graph theory
Logarithmic basis number of graphs
Knauer proves that every finite n-vertex multigraph satisfies bn(G)=O(logn), improving the previous general O(log2n) bound and matching the known Ω(logn) order. He also proves the sharper cycle-rank bound bn(G)=O(logβ(G)). Combined with a reduction of Lehner and Miraftab, this yields bn(G)=O(logg) for graphs of Euler genus g, improving the previous O(log2g) bound to the optimal logarithmic order.