Graciela Chichilnisky is one of them (as well as her co-authors). Late Beno Eckmann has a nice chapter in one of his books on "Social social choice theory " as a direct application of an average rule in arbitrary spaces. Other people include Luc Lauwers or Shmuel Weinberger. These are examples of mainly algebraic topology at work.
On the other hand, social choice theory is a wide area. It ranges from aggregating preferences to voting and even mechanism design to some extent where tools applied are different.
