Upper bounds on the upper signed total domination number of graphs

  • Authors:
  • Erfang Shan;T. C. E. Cheng

  • Affiliations:
  • Department of Mathematics, Shanghai University, Shanghai 200444, PR China and Department of Logistics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong;Department of Logistics, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong

  • Venue:
  • Discrete Applied Mathematics
  • Year:
  • 2009

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Abstract

Let G=(V,E) be a graph. A function f:V-{-1,+1} defined on the vertices of G is a signed total dominating function if the sum of its function values over any open neighborhood is at least one. A signed total dominating function f is minimal if there does not exist a signed total dominating function g, fg, for which g(v)@?f(v) for every v@?V. The weight of a signed total dominating function is the sum of its function values over all vertices of G. The upper signed total domination number of G is the maximum weight of a minimal signed total dominating function on G. In this paper we present a sharp upper bound on the upper signed total domination number of an arbitrary graph. This result generalizes previous results for regular graphs and nearly regular graphs.