3 problems

In second-order arithmetic, let $\textsf{RCA}_0$ and $\Pi^1_1\textsf{-CA}_0$ denote the indicated subsystems, and consider the theorem that inverse Goodstein sequences terminate, w…

The alternative normal forms in Example give rise to a terminating Goodstein process, but the methods in the paper do not establish lower bounds on such processes. Alternative Good…

Termination conjecture. Ackermannian Goodstein sequences will terminate for any reasonable notion of normal form.