The metamorphosis of lambda-fold block designs with block size four into maximum packings of lambda K-n with kites

Abstract

Let (X, B) be a lambda-fold block design with block size four and define sets B(K) and E(K-4 \ K) as follows: for each block b is an element of B, remove a path of length two, obtain a kite (a triangle with a tail), and place the kites in B(K) and the paths of length 2 in E(K-4 \ K). If we can reassemble the edges belonging to E(K-4 \ K) into a collection of kites E(K) with leave L, then (X, B(K) boolean OR E(K), L) is a packing of lambda K-n with kites. If vertical bar L vertical bar is as small as possible, then (X, B(K) boolean OR E(K), L) is called a metamorphosis of the lambda-fold block design (X, B) into a maximum packing of lambda K-n with kites. In this paper we give a complete solution of the metamorphosis problem for lambda-fold block designs with block size four into a maximum packing of lambda K-n with kites for all lambda. That is, for each lambda we determine the set of all n such that there exists a lambda-fold block design of order n having a metamorphosis into a maximum packing of lambda K-n with kites.