Bashicu matrix system: Difference between revisions

m
subscripts are now actually subscripts. hopefully all of them.
(made the page nontrivial)
m (subscripts are now actually subscripts. hopefully all of them.)
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- The parent of an entry x (a natural number in the array) is the last entry y before it in the same row, such that the entry directly above y (if it exists) is an ancestor of the entry above x, and y<x. The ancestors of an entry x are defined recursively as the parent of x and the ancestors of the parent of x.
 
- If A is empty, then A[n]=A for all natural numbers n. Otherwise let C be the last column of A, and let m0m<sub>0</sub> be maximal such that the m0m<sub>0</sub>-th element of C has a parent if such an m0 exists, otherwise m0m<sub>0</sub> is undefined. Let G and B0B<sub>0</sub> be arrays such that A=G+B0B<sub>0</sub>+(C), where + is concatenation, and the first column in B0B<sub>0</sub> contains the parent of the m0m<sub>0</sub>-th element of C if m0m<sub>0</sub> is defined, otherwise B0B<sub>0</sub> is empty.
 
- Say that an entry in B0B<sub>0</sub> "ascends" if it is in the first column of B0B<sub>0</sub> or has an ancestor in the first column of B0B<sub>0</sub>. Define B1B<sub>1</sub>,B2B<sub>2</sub>,...,BnB<sub>n</sub> as copies of B0B<sub>0</sub>, but in each BiB<sub>i</sub>, each ascending entry x is increased by i times the difference between the entry in C in the same row as x and the entry in the first column of B0B<sub>0</sub> in the same row as x.
 
- A[n]=G+B0B<sub>0</sub>+B1B<sub>1</sub>+...+BnB<sub>n</sub>, where + is again concatenation.
 
For a long time, the problem of finding a proof of its well-orderedness was a famous problem in apeirology, but now the proof is finished.<ref>Source will be added as soon as it's public, which should be approximately 3 hours after this edit.</ref> The proof utilizes [[stability]], so the problem of finding a self-contained proof that BMS is well-ordered remains open for now. A related open problem is the well-orderedness of Y sequence, which is similar enough to BMS (below the limit of BMS) that it can be considered an extension.
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