Graphs with large total domination number

  • Authors:
  • Michael A. Henning

  • Affiliations:
  • School of Mathematics, Statistics, & Information Technology, University of Natal, Private Bag X01, Scottsville, 3209 South Africa

  • Venue:
  • Journal of Graph Theory
  • Year:
  • 2000

Quantified Score

Hi-index 0.00

Visualization

Abstract

Let G = (V,E) be a graph. A set S⊆ V is a total dominating set if every vertex ofV is adjacent to some vertex in S. The totaldomination number of G, denoted byΥt(G), is the minimum cardinalityof a total dominating set of G. We establish a property ofminimum total dominating sets in graphs. If G is a connectedgraph of order n ≥ 3, then (see [3])Υt(G) ≤ 2n-3. We showthat if G is a connected graph of order n withminimum degree at least 2, then eitherΥt(G) ≤ 4n-7 or Gε {C3, C5,C6, C10}. A characterization ofthose graphs of order n which are edge-minimal with respectto satisfying G connected, δ(G) e 2 andΥt(G) ≥ 4n-7 isobtained. We establish that if G is a connected graph ofsize q with minimum degree at least 2, thenΥt(G) ≤(q + 2)-2.Connected graphs G of size q with minimum degree atleast 2 satisfying Υt(G) q-2 are characterized. © 2000 John Wiley & Sons,Inc. J Graph Theory 35: 2145, 2000