Generator-offset property: Difference between revisions
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Λ<sub>2</sub> = β W(β, β’) β’ | Λ<sub>2</sub> = β W(β, β’) β’ | ||
Λ<sub>3</sub> = γ W(γ, γ’) γ | Λ<sub>3</sub> = γ W(γ, γ’) γ | ||
where W is a word in two letters of length n | where W is a word in two letters of length n − 2. | ||
Since, by our assumption, Λ<sub>3</sub> has two γ’s in a row, Λ<sub>3</sub> must have more γ than γ’, so μ − 1 < n/2. Since Λ<sub>3</sub> is a mos, μ − 1 ≥ 1. So we have 2 ≤ μ ≤ ceil(n/2). | Since, by our assumption, Λ<sub>3</sub> has two γ’s in a row, Λ<sub>3</sub> must have more γ than γ’, so μ − 1 < n/2. Since Λ<sub>3</sub> is a mos, μ − 1 ≥ 1. So we have 2 ≤ μ ≤ ceil(n/2). | ||
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[Case 3: μ = anything else from 3 to floor(n/2). | [Case 3: μ = anything else from 3 to floor(n/2). | ||
Λ<sub>2</sub> has a chunk of βs (after the first β’) of size x = either floor(n/μ) (≥ floor(n/floor(n/2)) = 2) or ceil(n/μ) (= floor(n/μ) + 1). Hence Λ<sub>3</sub> has a chunk of γs of that same size. Λ<sub>3</sub> also has a chunk that goes over n and loops back around, which must be of size y = at least 2*(floor(n/μ) − 1) + 1 (Λ<sub>3</sub> might have chunks of size floor(n/μ) − 1 and floor(n/μ) instead) = 2*floor(n/μ) − 1, and at most 2*(floor(n/μ)+1) + 1 = 2*floor(n/μ) + 3 (if Λ<sub>3</sub> has chunks of size floor(n/μ) and ceil(n/μ)). The difference between the chunk sizes is y − x, which must be 0 or 1, since Λ<sub>3</sub> is a mos. We thus have the following cases: | Λ<sub>2</sub> has a chunk of βs (after the first β’) of size x = either floor(n/μ) (≥ floor(n/floor(n/2)) = 2) or ceil(n/μ) (= floor(n/μ) + 1). Hence Λ<sub>3</sub> has a chunk of γs of that same size. Λ<sub>3</sub> also has a chunk that goes over n and loops back around, which must be of size y = at least 2*(floor(n/μ) − 1) + 1 (Λ<sub>3</sub> might have chunks of size floor(n/μ) − 1 and floor(n/μ) instead) = 2*floor(n/μ) − 1, and at most 2*(floor(n/μ) + 1) + 1 = 2*floor(n/μ) + 3 (if Λ<sub>3</sub> has chunks of size floor(n/μ) and ceil(n/μ)). The difference between the chunk sizes is y − x, which must be 0 or 1, since Λ<sub>3</sub> is a mos. We thus have the following cases: | ||
BEGIN CASEBLOCK 3.x: [ Here chunk of Λ<sub>2</sub> means chunk of β, and chunk of Λ<sub>3</sub> means chunk of γ. | BEGIN CASEBLOCK 3.x: [ Here chunk of Λ<sub>2</sub> means chunk of β, and chunk of Λ<sub>3</sub> means chunk of γ. | ||
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Λ<sub>2</sub> has two consecutive chunks of size 1. Since chunk sizes form a mos, Λ<sub>2</sub> has more chunks of size 1 than it has chunks of size 2. | Λ<sub>2</sub> has two consecutive chunks of size 1. Since chunk sizes form a mos, Λ<sub>2</sub> has more chunks of size 1 than it has chunks of size 2. | ||
Use “w[i:j]” to denote the slice of the cyclic word w that includes both endpoints, i.e. the word w[i] w[i+1] ... w[j] where indices are taken to be elements of '''Z'''/n'''Z'''. Λ<sub>2</sub> has only two chunks of size 1, Λ<sub>2</sub>[(n − 1):(n − 1)] and Λ<sub>2</sub>[1:1], since otherwise Λ<sub>3</sub> would have a chunk of size 1 within Λ<sub>3</sub>[1:n − 1]. Thus Λ<sub>2</sub> has exactly one chunk of size 2. Thus Λ<sub>2</sub> = ββ’βββ’ββ’ and Λ<sub>3</sub> = γγ’γγγ’γγ. Thus we have: | Use “w[i:j]” to denote the slice of the cyclic word w that includes both endpoints, i.e. the word w[i] w[i + 1] ... w[j] where indices are taken to be elements of '''Z'''/n'''Z'''. Λ<sub>2</sub> has only two chunks of size 1, Λ<sub>2</sub>[(n − 1):(n − 1)] and Λ<sub>2</sub>[1:1], since otherwise Λ<sub>3</sub> would have a chunk of size 1 within Λ<sub>3</sub>[1:n − 1]. Thus Λ<sub>2</sub> has exactly one chunk of size 2. Thus Λ<sub>2</sub> = ββ’βββ’ββ’ and Λ<sub>3</sub> = γγ’γγγ’γγ. Thus we have: | ||
1 2 3 4 5 6 7 | 1 2 3 4 5 6 7 |