The Cartesian product of n cycles is a 2n-regular, 2n-connected and bi- pancyclic graph. Let G be the Cartesian product of n even cycles and let 2n = n1+ n2+ ・ ・ ・ + nkwith k ≥ 2 and ni≥ 2 for each i. We prove that if k = 2, then G can be decomposed into two spanning subgraphs G1and G2such that each Giis ni-regular, ni-connected, and bipancyclic or nearly bipancyclic. For k > 2, we establish that if all niin the partition of 2n are even, then G can be decomposed into k spanning subgraphs G1,G2, . . . ,Gk such that each Giis ni-regular and ni-connected. These results are analo- gous to the corresponding results for hypercubes.
Slater introduced the point-addition operation on graphs to characterize 4-connected graphs. The Г-extension operation on binary matroids is a generalization of the point-addition operation. In general, under the Г-extension operation the properties like graphicness and cographicness of matroids are not preserved. In this paper, we obtain forbidden minor characterizations for binary matroids whose Г-extension matroids are graphic (respectively, cographic).
The conditional h-vertex (h-edge) connectivity of a connected graph H of minimum degree k > h is the size of a smallest vertex (edge) set F of H such that H − F is a disconnected graph of minimum degree at least h. Let G be the Cartesian product of r ≥ 1 cycles, each of length at least four and let h be an integer such that 0 ≤ h ≤ 2r − 2. In this paper, we determine the conditional h-vertex-connectivity and the conditional h-edge-connectivity of the graph G. We prove that both these connectivities are equal to (2r−h)arh, where arh is the number of vertices of a smallest h-regular subgraph of G.