Two remarks on the adjoint polynomial

  • Authors:
  • Péter Csikvári

  • Affiliations:
  • -

  • Venue:
  • European Journal of Combinatorics
  • Year:
  • 2012

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Abstract

One can define the adjoint polynomial of the graph G as follows. Let a"k(G) denote the number of ways one can cover all vertices of the graph G by exactly k disjoint cliques of G. Then the adjoint polynomial of G is h(G,x)=@?k=1n(-1)^n^-^ka"k(G)x^k, where n denotes the number of vertices of the graph G. In this paper we show that the largest real root @c(G) of h(G,x) has the largest absolute value among the roots. We also prove that @c(G)@?4(@D-1), where @D denotes the largest degree of the graph G. This bound is sharp.