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Supersaturation in posets and applications involving the container method
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Noel, Jonathan A., Scott, Alex and Sudakov, Benny (2018) Supersaturation in posets and applications involving the container method. Journal of Combinatorial Theory, Series A, 154 . pp. 247-284. doi:10.1016/j.jcta.2017.08.019 ISSN 0097-3165.
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Official URL: http://dx.doi.org/10.1016/j.jcta.2017.08.019
Abstract
We consider ‘supersaturation’ problems in partially ordered sets (posets) of the following form. Given a finite poset P and an integer m greater than the cardinality of the largest antichain in P, what is the minimum number of comparable pairs in a subset of P of cardinality m? We provide a framework for obtaining lower bounds on this quantity based on counting comparable pairs relative to a random chain and apply this framework to obtain supersaturation results for three classical posets: the boolean lattice, the collection of subspaces of F n q ordered by set inclusion and the set of divisors of the square of a square-free integer under the ‘divides’ relation. The bound that we obtain for the boolean lattice can be viewed as an approximate version of a known theorem of Kleitman [23]. In addition, we apply our supersaturation results to obtain (a) upper bounds on the number of antichains in these posets and (b) asymptotic bounds on the cardinality of the largest antichain in p -random subsets of these posets which hold with high probability (for p in a certain range). The proofs of these results rely on a ‘container-type’ lemma for posets which generalises a result of Balogh, Mycroft and Treglown [6]. We also state a number of open problems regarding supersaturation in posets and counting antichains.
Item Type: | Journal Article | ||||||||
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Subjects: | Q Science > QA Mathematics | ||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Computer Science | ||||||||
Library of Congress Subject Headings (LCSH): | Ordered sets, Lattice theory, Boundary value problems -- Asymptotic theory | ||||||||
Journal or Publication Title: | Journal of Combinatorial Theory, Series A | ||||||||
Publisher: | Elsevier BV | ||||||||
ISSN: | 0097-3165 | ||||||||
Official Date: | February 2018 | ||||||||
Dates: |
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Volume: | 154 | ||||||||
Page Range: | pp. 247-284 | ||||||||
DOI: | 10.1016/j.jcta.2017.08.019 | ||||||||
Status: | Peer Reviewed | ||||||||
Publication Status: | Published | ||||||||
Access rights to Published version: | Restricted or Subscription Access | ||||||||
Date of first compliant deposit: | 12 July 2018 | ||||||||
Date of first compliant Open Access: | 14 September 2018 |
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