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Stijn Cambie, Recent progress on the Union-closed conjecture and related

Tuesday, March 14, 2023 @ 4:30 PM - 5:30 PM KST

Room B332, IBS (기초과학연구원)


Stijn Cambie
IBS Extremal Combinatorics and Probability Group

We give a summary on the work of the last months related to Frankl’s Union-Closed conjecture and its offsprings. The initial conjecture is stated as a theorem in extremal set theory; when a family F is union-closed (the union of sets of F is itself a set of $\mathcal F$), then $\mathcal F$ contains an (abundant) element that belongs to at least half of the sets. Meanwhile, there are many related versions of the conjecture due to Frankl. For example, graph theorists may prefer the equivalent statement that every bipartite graph has a vertex that belongs to no more than half of the maximal independent sets. While even proving the ε-Union-Closed Sets Conjecture was out of reach, Poonen and Cui & Hu conjectured already stronger forms.

At the end of last year, progress was made on many of these conjectures. Gilmer proved the ε-Union-Closed Sets Conjecture using an elegant entropy-based method which was sharpened by many others. Despite a sharp approximate form of the union-closed conjecture as stated by Chase and Lovett, a further improvement was possible. In a different direction, Kabela, Polak and Teska constructed union-closed family sets with large sets and few abundant elements.

This talk will keep the audience up-to-date and give them insight in the main ideas.

People who would like more details, can join the Ecopro-reading session on the 14th of March (10 o’clock, B332) as well. Here we go deeper in the core of the proofs and discuss possible directions for the full resolution.


Tuesday, March 14, 2023
4:30 PM - 5:30 PM KST
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Room B332
IBS (기초과학연구원) + Google Map


Sang-il Oum (엄상일)
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IBS 이산수학그룹 Discrete Mathematics Group
기초과학연구원 수리및계산과학연구단 이산수학그룹
대전 유성구 엑스포로 55 (우) 34126
IBS Discrete Mathematics Group (DIMAG)
Institute for Basic Science (IBS)
55 Expo-ro Yuseong-gu Daejeon 34126 South Korea
E-mail: dimag@ibs.re.kr, Fax: +82-42-878-9209
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