Suppose S is a set of maps to X . This suggests that the dual of unipotent map is called a nilpotent map . T such that fts factors through u . This shows that t is not disjoint with v . Hence v is unipotent.
Y are two unipotent maps.
Since f is a unipotent cover on X , t is not disjoint with f . This shows that any non-initial map t to X is not disjoint with fg , i.e. fg is unipotent. Assume fg is unipotent. X is a non-initial map. T such that tu factors through fg .