A new upper bound on the total domination number in graphs with minimum degree six

A total dominating set in a graph G is a set of vertices of G such that every vertex is adjacent to a vertex of the set. The total domination number γt(G) is the minimum cardinality of a dominating set in G. Thomassé and Yeo (2007) conjectured that if G is a graph on n vertices with minimum degree at least 5, then γt(G)≤411n. In this paper, it is shown that the Thomassé–Yeo conjecture holds with strict inequality if the minimum degree at least 6. More precisely, it is proven that if G is a graph of order n with δ(G)≥6, then γt(G)≤513814145n