2013/09/24 by Tait, Michael, Timmons, Craig · 1 citation
#Combinatorics (math.CO) #FOS: Mathematics
paper · doi:10.48550/arxiv.1309.6350
The problem of determining the maximum number of edges in an n-vertex graph that does not contain a 4-cycle has a rich history in extremal graph theory. Using Sidon sets constructed by Bose and Chowla, for each odd prime power q we construct a graph with q2 - q - 2 vertices that does not contain a 4-cycle and has at least (1)/(2)q3 - q2 - O(q3/4) edges. This disproves a conjecture of Abreu, Balbuena, and Labbate concerning the Turán number ex(q2 - q - 2, C4).