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Poset Power


A poset power B^A is the partially ordered set of isotone maps from a partially ordered set A to a partially ordered set B, ordered pointwise. Thus f<=g means f(a)<=g(a) for every a in A (Farley and Grätzer 2026). The partial order on the maps, rather than their composition, is the structure used in this definition.

Farley and Grätzer (2026) proved that, for finite nonempty partially ordered sets A and B, an order isomorphism A^A=B^B implies an order isomorphism A=B. This resolves Duffus's reconstruction question for poset powers (Farley and Grätzer 2026). It differs from poset reconstruction from one-element-deletion decks. The nonempty hypothesis matters, since the empty partially ordered set and the one-element partially ordered set both have a one-element self-power.


See also

Isotone Map, Order Isomorphism, Partially Ordered Set, Poset Reconstruction

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References

Farley, J. D. and Grätzer, G. "The A^A Problem for Finite Ordered Sets." 14 Oct 2026. https://arxiv.org/abs/2610.20817.

Cite this as:

Weisstein, Eric W. "Poset Power." From MathWorld--A Wolfram Resource. https://mathworld.wolfram.com/PosetPower.html

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