A functorial property of the Aczel-Buchholz-Feferman function
Andreas Weiermann · Journal of Symbolic Logic · 1994
Abstract Let Ω be the least uncountable ordinal. Let be the category where the objects are the countable ordinals and where the morphisms are the strictly monotonic increasing functions. A dilator is a functor on which preserves direct limits and pullbacks. Let τ Ω: ξ = ωξ}. Then τ has a unique “term”-representation in Ω. λξη.ωξ + η and countable ordinals called the constituents of τ. Let δ max{β.δ.ω}.