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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
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DTSTART:20200101T000000
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20211207T163000
DTEND;TZID=Asia/Seoul:20211207T173000
DTSTAMP:20260514T160255
CREATED:20211207T073000Z
LAST-MODIFIED:20240707T080616Z
UID:4804-1638894600-1638898200@dimag.ibs.re.kr
SUMMARY:Eun-Kyung Cho (조은경)\, Independent domination of graphs with bounded maximum degree
DESCRIPTION:The independent domination number of a graph $G$\, denoted $i(G)$\, is the minimum size of an independent dominating set of $G$. In this talk\, we prove a series of results regarding independent domination of graphs with bounded maximum degree. \nLet $G$ be a graph with maximum degree at most $k$ where $k \ge 1$. We prove that if $k = 4$\, then $i(G) \le \frac{5}{9}|V(G)|$\, which is tight. Generalizing this result and a result by Akbari et al.\, we suggest a conjecture on the upper bound of $i(G)$ for $k \ge 1$\, which is tight if true. \nLet $G’$ be a connected $k$-regular graph that is not $K_{k\, k}$ where $k\geq 3$. We prove that $i(G’)\le \frac{k-1}{2k-1}|V(G’)|$\, which is tight for $k \in \{3\, 4\}$\, generalizing a result by Lam\, Shiu\, and Sun. This result also answers a question by Goddard et al. in the affirmative. \nIn addition\, we show that $\frac{i(G’)}{\gamma(G’)} \le \frac{k^3-3k^2+2}{2k^2-6k+2}$\, strengthening upon a result of Knor\, Škrekovski\, and Tepeh\, where $\gamma(G’)$ is the domination number of $G’$. \nMoreover\, if we restrict $G’$ to be a cubic graph without $4$-cycles\, then we prove that $i(G’) \le \frac{4}{11}|V(G’)|$\, which improves a result by Abrishami and Henning. \nThis talk is based on joint work with Ilkyoo Choi\, Hyemin Kwon\, and Boram Park.
URL:https://dimag.ibs.re.kr/event/2021-12-07/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20211209T163000
DTEND;TZID=Asia/Seoul:20211209T173000
DTSTAMP:20260514T160255
CREATED:20211209T073000Z
LAST-MODIFIED:20240705T180040Z
UID:4671-1639067400-1639071000@dimag.ibs.re.kr
SUMMARY:David Munhá Correia\, Rainbow matchings
DESCRIPTION:I will discuss various results for rainbow matching problems. In particular\, I will introduce a ‘sampling trick’ which can be used to obtain short proofs of old results as well as to solve asymptotically some well known conjectures. This is joint work with Alexey Pokrovskiy and Benny Sudakov.
URL:https://dimag.ibs.re.kr/event/2021-12-09/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
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BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20211214T163000
DTEND;TZID=Asia/Seoul:20211214T173000
DTSTAMP:20260514T160255
CREATED:20211214T073000Z
LAST-MODIFIED:20240705T180035Z
UID:4913-1639499400-1639503000@dimag.ibs.re.kr
SUMMARY:Tuan Tran\, Exponential decay of intersection volume with applications on list-decodability and sphere-covering bounds
DESCRIPTION:We give some natural sufficient conditions for balls in a metric space to have small intersection. Roughly speaking\, this happens when the metric space is (i) expanding and (ii) well-spread\, and (iii) certain random variable on the boundary of a ball has a small tail. As applications\, we show that the volume of intersection of balls in Hamming space and symmetric groups decays exponentially as their centers drift apart. To verify condition (iii)\, we prove some deviation inequalities `on the slice’ for functions with Lipschitz conditions. \nWe then use these estimates on intersection volumes to \n\nobtain a sharp lower bound on list-decodability of random q-ary codes\, confirming a conjecture of Li and Wootters [IEEE Trans. Inf. Theory 2021]; and\nimprove sphere-covering bound from the 70s on constant weight codes by a factor linear in dimension\, resolving a problem raised by Jiang and Vardy [IEEE Trans. Inf. Theory 2004].\n\nOur probabilistic point of view also offers a unified framework to obtain improvements on other sphere-covering bounds\, giving conceptually simple and calculation-free proofs for q-ary codes\, permutation codes\, and spherical codes. \nThis is joint work with Jaehoon Kim and Hong Liu.
URL:https://dimag.ibs.re.kr/event/2021-12-14/
LOCATION:Room B232\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
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BEGIN:VEVENT
DTSTART;VALUE=DATE:20211220
DTEND;VALUE=DATE:20211223
DTSTAMP:20260514T160255
CREATED:20211219T150000Z
LAST-MODIFIED:20240707T080557Z
UID:4146-1639958400-1640217599@dimag.ibs.re.kr
SUMMARY:2021 Combinatorics Workshop (2021 조합론 학술대회)
DESCRIPTION:The Combinatorics Workshop (조합론 학술대회) is an annual conference of combinatorialists in Korea that started in 2004 by the Yonsei University BK21 Research Group. Since 2013\, this workshop has been advised by the committee of discrete mathematics of the Korean Mathematical Society. This year it will take place at The Bloomvista in Yangpyeong on December 20-22\, 2021. \nThe aim of this workshop is to bring together active researchers with different backgrounds to discuss recent and prospective advances in combinatorics and related areas. \nWe plan to limit the number of participants. Registration (without a fee) will be required. General participants will be required to pay for their own accommodation. \n\nTitle: 2021 Combinatorics Workshop (2021 조합론 학술대회)\nDate: December 20 – 22 (Mon-Wed)\, 2021\nVenue: The Bloomvista\, Yangpyeong\nWebsite: https://cw2021.combinatorics.kr\n\nPlan\n\nStarting in the afternoon of Thursday and ending in the morning of Wednesday.\nThere will be 5 invited talks for 50 minutes each.\nThere will be contributed talks for 25 minutes each.\n\nUsing English is recommended if there are non-Korean participants in the audience.\nThe call for contributed talks will be announced later.\n\n\nIt will be an offline meeting.\n\nInvited Speakers\n\nDongsu Kim\, KAIST\nJoonkyung Lee\, Hanyang University\nHong Liu\, University of Warwick\, UK\nSuil O\, SUNY Korea\nSeonjeong Park\, Jeonju University\n\nCall for Abstracts\nWe are looking for contributed talks! If you are interested in giving a contributed talk\, then please submit your abstract until November 15\, 2021. \nRegistration\n\nPlease fill out the registration form by November 21\, 2021.\n\nThe registration is free.\nThe organizers will announce the price for the accommodation soon.\n\n\nDue to the government COVID-19 policy\, the organizers may reject some registration\, even if the registration was made before November 21.\n\nOrganizing Committee\n\nJeong-Ok Choi\, GIST\nSang-il Oum\, IBS Discrete Mathematics Group and KAIST\nHeesung Shin\, Inha University\n\nAdvisory Committee\nCommittee of Discrete Mathematics\, The Korean Mathematical Society (Chair: Soojin Cho\, Ajou University) \nHost and Sponsors\nIBS Discrete Mathematics Group
URL:https://dimag.ibs.re.kr/event/2021-combinatorics-workshop/
LOCATION:The Bloomvista
CATEGORIES:Workshops and Conferences
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