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The smallest degree sum that yields potentially K_{r+1}-Z-graphical Sequences

Combinatorics 2009-11-17 v3

Abstract

Let KmHK_{m}-H be the graph obtained from KmK_{m} by removing the edges set E(H)E(H) of the graph HH (HH is a subgraph of KmK_{m}). We use the symbol Z4Z_4 to denote K4P2.K_4-P_2. A sequence SS is potentially KmHK_{m}-H-graphical if it has a realization containing a KmHK_{m}-H as a subgraph. Let σ(KmH,n)\sigma(K_{m}-H, n) denote the smallest degree sum such that every nn-term graphical sequence SS with σ(S)σ(KmH,n)\sigma(S)\geq \sigma(K_{m}-H, n) is potentially KmHK_{m}-H-graphical. In this paper, we determine the values of σ(Kr+1Z,n)\sigma (K_{r+1}-Z, n) for n5r+19,r+1k5,n\geq 5r+19, r+1 \geq k \geq 5, j5j \geq 5 where ZZ is a graph on kk vertices and jj edges which contains a graph Z4Z_4 but not contains a cycle on 4 vertices. We also determine the values of σ(Kr+1Z4,n)\sigma (K_{r+1}-Z_4, n), σ(Kr+1(K4e),n)\sigma (K_{r+1}-(K_4-e), n), σ(Kr+1K4,n)\sigma (K_{r+1}-K_4, n) for n5r+16,r4n\geq 5r+16, r\geq 4. There are a number of graphs on kk vertices and jj edges which contains a graph Z4Z_4 but not contains a cycle on 4 vertices.

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Cite

@article{arxiv.math/0608245,
  title  = {The smallest degree sum that yields potentially K_{r+1}-Z-graphical Sequences},
  author = {Chunhui Lai},
  journal= {arXiv preprint arXiv:math/0608245},
  year   = {2009}
}

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13 pages