number-theory / Equidistribution mod 1

(ξαn)n1(\xi\alpha^n)_{n\ge1} is not uniformly distributed modulo one for Pisot α\alpha and ξ\xi in the Cantor set C(α)C(\alpha)

Bugeaud's Problem 10.61, due to Michel Mendès France in 1967: for a Pisot number α>2\alpha > 2 and the Cantor set C(α)={(α1)k1εkαk:εk{0,1}}C(\alpha) = \{(\alpha-1)\sum_{k\ge1}\varepsilon_k\alpha^{-k} : \varepsilon_k \in \{0,1\}\}, no ξC(α)\xi \in C(\alpha) has (ξαn)n1(\xi\alpha^n)_{n\ge1} uniformly distributed modulo one. The problem itself remains open. What is proved is a set of criteria for it, and two instances. The criteria: a reduction to symbolic dynamics that is an equivalence; a pressure criterion; and a covering criterion which, for a quadratic setup of norm bb, applies exactly when (log2α1)(log2(α/b)1)>1(\log_2\alpha - 1)(\log_2(\alpha/|b|) - 1) > 1, a condition that reduces to α>4\alpha > 4 for units. The two instances are both quadratic: at α=2+5\alpha = 2+\sqrt5 in the strong form, an explicit interval that every orbit misses at every time, and at α=2+3\alpha = 2+\sqrt3 by a confinement-gap certificate.

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number-theoryAug 31, 2026Significance 22/100Registry: lean checked

(ξαn)n1(\xi\alpha^n)_{n\ge1} is not uniformly distributed modulo one for Pisot α\alpha and ξ\xi in the Cantor set C(α)C(\alpha)

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The problem is open, and the repository says so: what is proved are criteria for it and two instances, not the general case. Every compared statement that concludes Problem 10.61 does so for a quadratic setup - a real root α>1\alpha > 1 of X2aXbX^2 - aX - b whose conjugate has modulus below one - and both instances are quadratic. The arbitrary-degree material is conditional ingredients: for the family…

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Bugeaud's Problem 10.61, due to Michel Mendès France in 1967: for a Pisot number α>2\alpha > 2 and the Cantor set C(α)={(α1)k1εkαk:εk{0,1}}C(\alpha) = \{(\alpha-1)\sum_{k\ge1}\varepsilon_k\alpha^{-k} : \varepsilon_k \in \{0,1\}\}, no ξC(α)\xi \in C(\alpha) has (ξαn)n1(\xi\alpha^n)_{n\ge1} uniformly distributed modulo one. The problem itself remains open. What is proved is a set of criteria for it, and two instances. The criteria: a reduction to symbolic dynamics that is an equivalence; a pressure criterion; and a covering criterion which, for a quadratic setup of norm bb, applies exactly when (log2α1)(log2(α/b)1)>1(\log_2\alpha - 1)(\log_2(\alpha/|b|) - 1) > 1, a condition that reduces to α>4\alpha > 4 for units. The two instances are both quadratic: at α=2+5\alpha = 2+\sqrt5 in the strong form, an explicit interval that every orbit misses at every time, and at α=2+3\alpha = 2+\sqrt3 by a confinement-gap certificate.

The problem is open, and the repository says so: what is proved are criteria for it and two instances, not the general case. Every compared statement that concludes Problem 10.61 does so for a quadratic setup - a real root α>1\alpha > 1 of X2aXbX^2 - aX - b whose conjugate has modulus below one - and both instances are quadratic. The arbitrary-degree material is conditional ingredients: for the family XdaXd11X^d - aX^{d-1} - 1 the real root exceeding aa is shown to be Pisot for a3a \ge 3, with a conjugate-modulus bound and a numerical inequality. No compared statement carries those above degree two, because the covering criterion is proved only for quadratic setups. The covering criterion also leaves quadratic α\alpha with route-A exponent at least one undecided, about which nothing is claimed.

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