n-transitive group action 2026-10-14
A group action on a set is n-transitive when it can send any ordered tuple of distinct points to any other such tuple. Here ordered means a sequence of entries, not increasing in a total order. For order-preserving actions the corresponding notion is order n-transitivity.
Here transitivity is order n-transitivity: increasing tuples are compared, rather than arbitrary reorderings. For increasing tuples and , choose sending both to and to when , using order two-transitivity. For , choose an element sending the single point to its target, using transitivity. Define
Figure 1.
Finite order interpolation constructed from pointwise minima and maxima
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This belongs to the lattice-ordered permutation group. At , all terms in its th inner meet equal . At , every inner meet is at most , because its term takes that value. The outer join is consequently exactly there. Thus maps the whole tuple to its target. This finite interpolation by lattice operations proves every finite order-transitivity without assuming the group permits arbitrary cut-and-paste restrictions of its elements.