The substitution lemma for Scott complexity of finite-rank trees
The substitution lemma for Scott complexity of finite-rank trees
Let . Write for the canonical tree of rank , and let be the tree obtained by deleting all but of the level-one subtrees of type . Thus . A root of a -subtree may be relocated to a fresh root of a -subtree, with witnesses carried to matched witnesses. Substitution lemma, two prongs. For every , (a) every formula true in of a tuple consisting of such a root and arbitrary witnesses remains true after relocation for all sufficiently large finite ; and (b) for every and every tuple satisfying , if exceeds the number of -roots named by , then by re-hosting the inner witnesses inside . Consequently, these two substitution principles should exclude , , and Scott sentences for , and yield
This would provide a purely combinatorial proof of the general Scott-complexity theorem, without computability, and would localize the non--definable orbit at . The program is stated to remain open for .
Progress summary
Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.
Sources & referencesView supporting material
Primary source
Mohammad Mahmoud and Mostafa Mirabi, “Scott complexity of trees of finite rank via degrees of categoricity”, arXiv:2606.27151 (2026).
Solutions 0
Sign in to submit a solution.
No solutions have been posted yet.