Deuber's wqo theorem
Let (A,<) be a wqo-set with an obvious ranking r defined by successively taking minimal elements. Call a sequence (a0,a1,...) regressive iff r(ai)<i for every i in ω.
Theorem (Deuber): Let (A,<) be wqo. Then there exists a function
H(A,<):ω --> ω such that every regressive sequence (a0,a1,...,aH(n)) contains a weakly ascending subsequence with n terms.
Three Variable Funny Test
Ben Folds is playing at Allegheny College. Beverly, can you get Fab and me student tickets? We're cheap and we don't want to pay full price.
Theorem (Deuber): Let (A,<) be wqo. Then there exists a function
H(A,<):ω --> ω such that every regressive sequence (a0,a1,...,aH(n)) contains a weakly ascending subsequence with n terms.
Three Variable Funny Test
Ben Folds is playing at Allegheny College. Beverly, can you get Fab and me student tickets? We're cheap and we don't want to pay full price.
posted by Landon at 12:56 AM
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