A point on fixpoints in posets. F. Blanqui. Note. 2014.
Let (X,≤) be a non-empty strictly inductive poset, that is, a non-empty partially ordered set such that every non-empty chain Y has a least upper bound lub(Y)∈X, a chain being a subset of X totally ordered by ≤. We are interested in sufficient conditions such that, given an element a0∈X and a function f:X→X, there is some ordinal k such that ak+1=ak, where ak is the transfinite sequence of iterates of f starting from a0 (ak is then a fixpoint of f):