# Rank-3 scale theorems

(Redirected from User:Inthar/Recursive structure of rank-3 scales)

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## Theorems

- Every triple Fokker block is max variety 3.
- Every max variety 3 block is a triple Fokker block. (However, not every max-variety 3 scale, in general, need be a Fokker block.)
- Triple Fokker blocks form a trihexagonal tiling on the lattice.
- A scale imprint is that of a Fokker block if and only if it is the product word of two DE scale imprints with the same number of notes. See Introduction to Scale Theory over Words in Two Dimensions | SpringerLink
- If the step sizes for a rank-3 Fokker block are L, m, n, and s, where L > m > n > s, then the following identity must hold: (n-s) + (m-s) = (L-s), hence n+m=L+s
- Any convex object on the lattice can be converted into a hexagon.
- Any convex scale with 3 step sizes is a hexagon on the lattice, in which each set of parallel lines corresponds to one of the steps.
- A pairwise-well-formed scale has odd size, and is either generator-offset or of the form abacaba.

## Unproven Conjectures

- Every rank-3 Fokker block has mean-variety < 4, meaning that some interval class will come in less than 4 sizes.

## MV3 proofs

Under construction

### Definitions and theorems

Throughout, let *S* be a scale word in steps *x*, *y*, *z* (and assume all three of these letters are used).

#### Definition: Unconditionally MV3

An abstract scale word *S* is *MV3*, *unconditionally MV3* or *abstractly MV3* if *S* is MV3 for all possible choices of step ratio x:y:z.

#### Definition: EMOS

*S* is *elimination-MOS* (EMOS) if the result of removing (all instances of) any one of the step sizes is a MOS.

#### Definition: PMOS

*S* is *pairwise MOS* (PMOS) if the result of equating any two of the step sizes is a MOS.

#### Definition: GO

*S* satisfies the *generator-offset property* (GO) if it satisfies the following equivalent properties:

*S*can be built by stacking a single chain of alternating generators g1 and g2, resulting in a circle of the form either g1 g2 ... g1 g2 g1 g3 or g1 g2 ... g1 g2 g3.*S*is generated by two chains of generators separated by a fixed interval; either both chains are of size*m*, or one chain has size*m*and the second has size*m-1*.

These are equivalent, since the separating interval can be taken to be g1 and the generator of each chain = g1 + g2.

For theorems relating to the GO property, see generator-offset property.