On Large Circuits in Matroids

M

be a matroid with a maximum-sized circuit C of size at least four. This paper proves that, for k∈{2,3}, if M is k-connected, then every element of M is contained in a circuit of size at least . Even when M is 3-connected and binary, the presence of a large circuit in M does not guarantee that M has a large circuit containing a nominated pair of elements. However, when M is 3-connected and graphic, it will be shown that every pair of distinct elements is contained in a circuit of at least . Examples will be given to show that these results are best-possible and some related results will also be proved.