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Universal Positivity Set

Can one construct an infinite recursively enumerable set S⊂NS\subset \mathbb{N}, for which one can decide: given any linear recurrence sequence (un)(u_n), whether ∃n∈S\exists n\in S, s.t. un<0u_n<0 ? In other words: is there a set of indices for which the positivity problem is decidable? The analogous question where un<0u_n<0 is replaced by un=0u_n=0 has a positive answer for simple sequences; Luca, Ouaknine and Worrell have constructed such a set explicitly (called the universal Skolem set).

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Organizer

Boyuan Wang portraitBoyuan Wang
Minghan Wang portraitMinghan Wang
Bochao Li portraitBochao Li
Hongwei Hu portraitHongwei Hu