The Turán number for the edge blow-up of trees

Abstract

The edge blow-up of a graph F is the graph obtained from replacing each edge in F by a clique of the same size where the new vertices of the cliques are all different. In this article, we consider the Turán problem for the edge blow-up of trees. Erdős et al. (1995) [9] and Chen et al. (2003) [5] solved the problem for stars. The problem for paths was resolved by Glebov (2011) [10]. Liu (2013) [15] extended the above results to cycles and a special family of trees with minimum degree at most two in the smaller color class (paths and proper subdivisions of stars were included in the family). In this article, we extend Liu's result to all the trees with minimum degree at least two in the smaller color class. Combining with Liu's result, except one particular case, the Turán problem for the edge blow-up of trees is completely resolved. Moreover, we determine the maximum number of edges in the family of {K1,k,kK2,2K1,k−1}-free graphs and the extremal graphs, which is an extension of a result given by Abbott et al. (1972) [1].