All Questions

Gostanian's paper "The next admissible ordinal" (see https://www.sciencedirect.com/science/article/pii/0003484379900251 ), is concerned with the supremum of the $\alpha$-recursive ordinals for various ...

Consider the following statement (which follows easily from various results found in the literature): (†) There exists a primitive recursive (“p.r.”) relation $T$ on the ordinals such that, if $(...

An ordinal $\alpha$ is said to be computable if there is a computable relation on a subset of integers that is well-ordered and its order type equals $\alpha$. But let's consider well-founded trees on ...