Robust Matchings and Maximum Clustering

We consider complete graphs with nonnegative edge weights. A p-matching is a set of p disjoint edges. We prove the existence of a maximal (with respect to inclusion) matching M that contains for any p ≤ |M| p edges whose total weight is at least 1/√2 of the maximum weight of a p-matching. We use this property to approximate graph partitioning problems in which the sizes of the parts of the partitioning are given.