The core-partition of a hedonic game

In a hedonic game the preference relation of each player is defined on the set of coalitions that contain the player. The paper provides a necessary and sufficient condition for core-partition existence in a hedonic game. The condition is based on a new concept of balancedness, called pivotal balancedness, involving subsets of players in any given family of coalitions. Pivotal balancedness highlights the existence of key players in each coalition that are relevant for the existence of a core-partition.