Authors: Jojić, DuškoPanina, GaianeŽivaljević, Rade Affiliations: Mechanics Mathematical Institute of the Serbian Academy of Sciences and Arts Title: Splitting necklaces, with constraints Journal: SIAM Journal on Discrete Mathematics Volume: 35 Issue: 2 First page: 1268 Last page: 1286 Issue Date: 2021 Rank: ~M23 ISSN: 0895-4801 DOI: 10.1137/20M1331949 Abstract: We prove several versions of Alon's necklace-splitting theorem, subject to additional constraints, as illustrated by the following results. (1) The "almost equicardinal necklace-splitting theorem" claims that, without increasing the number of cuts, one guarantees the existence of a fair splitting such that each thief is allocated almost the same number of pieces of the necklace (including "degenerate pieces" if they exist), provided the number of thieves r = p\nu is a prime power. By "almost the same" we mean that for each pair of thieves one of them can be given at most one piece more (one piece less) than the other. (2) The "binary splitting theorem" claims that if r = 2d and the thieves are associated with the vertices of a d-cube, then, without increasing the number of cuts, one can guarantee the existence of a fair splitting such that adjacent pieces are allocated to thieves that share an edge of the cube. This result provides a positive answer to the "binary splitting necklace conjecture" in the case r = 2d from Conjecture 2.11 in [M. Asada et al., SIAM J. Discrete Math., 32 (2018), pp. 591-610]. (3) An interesting variation arises when the thieves have their own individual preferences. We prove several envy-free, fair necklace-splitting theorems of various level of generality, as illustrated by the envy-free versions of (a) Alon's original necklace-splitting theorem, (b) the almost equicardinal splitting theorem, and (c) the binary splitting theorem, etc. Keywords: Collectively unavoidable complexes | Configuration space/test map scheme | Envy-free division | Necklace-splitting theorem Publisher: SIAM

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