English

On the approximate shape of degree sequences that are not potentially $H$-graphic

Combinatorics 2013-03-25 v1

Abstract

A sequence of nonnegative integers π\pi is {\it graphic} if it is the degree sequence of some graph GG. In this case we say that GG is a \textit{realization} of π\pi, and we write π=π(G)\pi=\pi(G). A graphic sequence π\pi is {\it potentially HH-graphic} if there is a realization of π\pi that contains HH as a subgraph. Given nonincreasing graphic sequences π1=(d1,,dn)\pi_1=(d_1,\ldots,d_n) and π2=(s1,,sn)\pi_2 = (s_1,\ldots,s_n), we say that π1\pi_1 {\it majorizes} π2\pi_2 if disid_i \geq s_i for all ii, 1in1 \leq i \leq n. In 1970, Erd\H{o}s showed that for any Kr+1K_{r+1}-free graph HH, there exists an rr-partite graph GG such that π(G)\pi(G) majorizes π(H)\pi(H). In 2005, Pikhurko and Taraz generalized this notion and showed that for any graph FF with chromatic number r+1r+1, the degree sequence of an FF-free graph is, in an appropriate sense, nearly majorized by the degree sequence of an rr-partite graph. In this paper, we give similar results for degree sequences that are not potentially HH-graphic. In particular, there is a graphic sequence π(H)\pi^*(H) such that if π\pi is a graphic sequence that is not potentially HH-graphic, then π\pi is close to being majorized by π(H)\pi^*(H). Similar to the role played by complete multipartite graphs in the traditional extremal setting, the sequence π(H)\pi^*(H) asymptotically gives the maximum possible sum of a graphic sequence π\pi that is not potentially HH-graphic.

Keywords

Cite

@article{arxiv.1303.5622,
  title  = {On the approximate shape of degree sequences that are not potentially $H$-graphic},
  author = {Catherine Erbes and Michael Ferrara and Ryan R. Martin and Paul Wenger},
  journal= {arXiv preprint arXiv:1303.5622},
  year   = {2013}
}

Comments

19 pages