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X-WR-CALNAME:Discrete Mathematics Group
X-ORIGINAL-URL:https://dimag.ibs.re.kr
X-WR-CALDESC:Events for Discrete Mathematics Group
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TZID:Asia/Seoul
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TZOFFSETFROM:+0900
TZOFFSETTO:+0900
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DTSTART:20240101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20250902T163000
DTEND;TZID=Asia/Seoul:20250902T173000
DTSTAMP:20260416T124154
CREATED:20250804T030207Z
LAST-MODIFIED:20250804T040402Z
UID:11325-1756830600-1756834200@dimag.ibs.re.kr
SUMMARY:Zhifei Yan\, A Rainbow version of Lehel's conjecture
DESCRIPTION:Lehel’s conjecture states that every 2-edge-colouring of the complete graph $K_n$ admits a partition of its vertices into two monochromatic cycles. This was proven for sufficiently large n by Luczak\, Rödl\, and Szemerédi (1998)\, extended by Allen (2008)\, and fully resolved by Bessy and Thomassé in 2010. \nWe consider a rainbow version of Lehel’s conjecture for properly edge-coloured complete graphs. We prove that for any properly edge-coloured $K_n$ with sufficiently large n\, there exists a partition of the vertex set into two rainbow cycles\, each containing no two edges of the same colour. \nThis is joint work with Pedro Araújo\, Xiaochuan Liu\, Taísa Martins\, Walner Mendonça\, Luiz Moreira\, and Vinicius Fernandes dos Santos.
URL:https://dimag.ibs.re.kr/event/2025-09-02/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20250909T163000
DTEND;TZID=Asia/Seoul:20250909T173000
DTSTAMP:20260416T124154
CREATED:20250812T235708Z
LAST-MODIFIED:20250827T143840Z
UID:11356-1757435400-1757439000@dimag.ibs.re.kr
SUMMARY:Katherine Perry\, Symmetry breaking in trees
DESCRIPTION:We will discuss two symmetry breaking parameters: distinguishing number and fixing number. Despite being introduced independently\, they share meaningful connections. In particular\, we show that if a tree is 2-distinguishable with order at least 3\, it suffices to fix at most 4/11 of the vertices and if a tree is $d$-distinguishable\, $d \geq 3$\, it suffices to fix at most $\frac{d-1}{d+1}$ of the vertices. We also characterize the $d$-distinguishable trees with radius $r$\, for any $d \geq 2$ and $r \geq 1$. \nThis is joint work with Calum Buchanan\, Peter Dankleman\, Isabel Harris\, Paul Horn\, and Emily Rivett-Carnac.
URL:https://dimag.ibs.re.kr/event/2025-09-09/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20250916T163000
DTEND;TZID=Asia/Seoul:20250916T173000
DTSTAMP:20260416T124154
CREATED:20250822T095250Z
LAST-MODIFIED:20250822T095250Z
UID:11440-1758040200-1758043800@dimag.ibs.re.kr
SUMMARY:Mujin Choi (최무진)\, Excluding ladder and wheel as induced minor in graphs without induced stars
DESCRIPTION:We prove that for all positive integers $k$ and $d$\, the class of $K_{1\,d}$-free graphs not containing the $k$-ladder or the $k$-wheel as an induced minor has a bounded tree-independence number. Our proof uses a generalization of the concept of brambles to tree-independence number. This is based on joint work with Claire Hilaire\, Martin Milanič\, and Sebastian Wiederrecht.
URL:https://dimag.ibs.re.kr/event/2025-09-16/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20250922T163000
DTEND;TZID=Asia/Seoul:20250922T173000
DTSTAMP:20260416T124154
CREATED:20250820T143638Z
LAST-MODIFIED:20250829T000026Z
UID:11429-1758558600-1758562200@dimag.ibs.re.kr
SUMMARY:Rong Luo\, Modulo flows and Integer flows  of signed graphs
DESCRIPTION:Nowhere-zero flows of unsigned graphs were introduced by Tutte in 1954 as a dual problem to vertex-coloring of (unsigned) planar graphs. The definition of nowhere-zero flows on signed graphs naturally comes from the study of embeddings of graphs in non-orientable surfaces\, where nowhere-zero flows emerge as the dual notion to local tensions.  Nowhere-zero flows in signed graphs were introduced by Edmonds and Johnson in 1970 for expressing algorithms on matchings\, but systematically studied first by Bouchet in 1983. Bouchet also stated a conjecture which occupies a central place in the area of signed graphs: Every flow-admissible signed graph admits a nowhere-zero 6-flow.  There is a significant difference in the flows of signed graphs and unsigned graphs. In this talk I will talk about the progress on the development of the flow theory of signed graphs.
URL:https://dimag.ibs.re.kr/event/2025-09-22/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20250930T163000
DTEND;TZID=Asia/Seoul:20250930T173000
DTSTAMP:20260416T124154
CREATED:20250822T151431Z
LAST-MODIFIED:20250902T021816Z
UID:11444-1759249800-1759253400@dimag.ibs.re.kr
SUMMARY:Marcelo Sales\, On the Ramsey number of Daisies and other hypergraphs
DESCRIPTION:Given a $k$-uniform hypergraph $H$\, the Ramsey number $R(H;q)$ is the smallest integer $N$ such that any $q$-coloring of the edges of the complete $k$-uniform hypergraph on $N$ vertices contains a monochromatic copy of $H$. \nWhen $H$ is a complete hypergraph\, a classical argument of Erdős\, Hajnal\, and Rado reduces the general problem to the case of uniformity $k = 3$. In this talk\, we will survey constructions that lift Ramsey numbers to higher uniformities and discuss recent progress on quantitative bounds for $R(H;q)$ for certain families of hypergraphs. \nThis is joint work with Ayush Basu\, Dániel Dobák\, Pavel Pudlák\, and Vojtěch Rödl.
URL:https://dimag.ibs.re.kr/event/2025-09-30/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
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