We propose two new measures of conditional connectivity to be the extension of Rg-connectivity and Rg-edge-connectivity. Let G be a connected graph. A set of vertices (edges) F is said to be a conditional (g, d, k)(-edge)-cut of G if (1) G – F is disconnected; (2) every vertex in G – F has at least g neighbors; (3) degG–F(p) + degG–F(q) ≥ 2g + k for every two distinct vertices p and q in G – F with d(p, q) ≤ d. The (g, d, k)-conditional(-edge)-connectivity, denoted by κg,d,k(λg,d,k), is the minimum cardinality of a conditional (g, d, k)(-edge)-cut. Based on these requirements, we obtain κ1,1,k, κ1,d,2, λ1,1,1 and λ1,d,2 for the hypercubes.
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For a network, edge/node-independent spanning trees (ISTs) can not only tolerate faulty edges/nodes, but also be used to distribute secure messages. As important node-symmetric variants of the hypercubes, the augmented cubes have received much attention from researchers. The n-dimensional augmented cube AQn is both (2n ‒ 1)-edge-connected and (2n ‒ 1)-nodeconnected (n≠3), thus the well-known edge conjecture and node conjecture of ISTs are both interesting questions in AQn. So far, the edge conjecture on augmented cubes was proved to be true. However, the node conjecture on AQn is still open. In this paper, we further study the construction principle of the node-ISTs by using the double neighbors of every node in the higher dimension. We prove the existence of 2k − 1 node-ISTs rooted at node 0 in AQn ( 00...0 n – k ) ( n ≥ k ≥ 4 ) by proposing an ingenious way of construction and propose a corresponding O (N logN ) time algorithm, where N = 2k is the number of nodes in AQn ( 00...0 n – k ) .
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