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October 2019

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Joonkyung Lee (이준경), On some properties of graph norms

Speaker

Joonkyung Lee (이준경)
Department of Mathematics, University of Hamburg, Germany
https://sites.google.com/site/joonkyungleemaths/
October 22 Tuesday @ 4:30 PM - 5:30 PM
Room B232, IBS (기초과학연구원)

For a graph $H$, its homomorphism density in graphs naturally extends to the space of two-variable symmetric functions $W$ in $L^p$, $p\geq e(H)$, denoted by $t_H(W)$. One may then define corresponding functionals $\|W\|_{H}:=|t_H(W)|^{1/e(H)}$ and $\|W\|_{r(H)}:=t_H(|W|)^{1/e(H)}$ and say that $H$ is (semi-)norming if $\|.\|_{H}$ is a (semi-)norm and that $H$ is weakly norming if $\|.\|_{r(H)}$ is a norm. We obtain some results that contribute to the theory of (weakly) norming graphs. Firstly, we show that 'twisted' blow-ups of cycles, which include…

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Extremal and Structural Graph Theory (2019 KMS Annual Meeting)

October 26 Saturday - October 27 Sunday
Room 426, Hong-Mun Hall, Hongik University, Seoul

Focus Session @ 2019 KMS Annual MeetingA focus session "Extremal and Structural Graph Theory" at the 2019 KMS Annual Meeting is organized by Sang-il Oum. URL: http://www.kms.or.kr/meetings/fall2019/SpeakersIlkyoo Choi (최일규), Hankuk University of Foreign StudiesKevin Hendrey, IBS Discrete Mathematics GroupPascal Gollin, IBS Discrete Mathematics GroupJaehoon Kim (김재훈), KAISTRingi Kim (김린기), KAISTSeog-Jin Kim (김석진), Konkuk UniversityO-joung Kwon (권오정), Incheon National University / IBS Discrete Mathematics GroupZi-Xia Song (宋梓霞), University of Central FloridaCasey Tompkins, IBS Discrete Mathematics GroupSchedulesSlot A: October 26, 2019 Saturday, 9:00am-10:15amSeog-Jin KimKevin HendreyIlkyoo ChoiSlot…

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The 2nd East Asia Workshop on Extremal and Structural Graph Theory

October 31 Thursday - November 4 Monday
UTOP UBLESS Hotel, Jeju, Korea (유탑유블레스호텔제주)

The 2nd East Asia Workshop on Extremal and Structural Graph Theory is a workshop to bring active researchers in the field of extremal and structural graph theory, especially in the East Asia such as China, Japan, and Korea.DateOct 31, 2019 (Arrival Day) - Nov 4, 2019 (Departure Day)Venue and DateUTOP UBLESS Hotel, Jeju, Korea (유탑유블레스호텔제주) Address: 502 Johamhaean-ro, Jocheon-eup, Jeju, Korea (제주특별자치도 제주시 조천읍 조함해안로 502) We plan to support the accommodation for invited participants. The UTOP UBLESS Hotel is…

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November 2019

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Combinatorial and Discrete Optimization (2019 KSIAM Annual Meeting)

November 8 Friday @ 12:00 PM - November 9 Saturday @ 7:00 PM
Venezia Hotel & Resort Yeosu, Yeosu, Korea (여수 베네치아 호텔) 

Special Session @ 2019 KSIAM Annual Meeting A special session on "Combinatorial and Discrete Optimization" at the 2019 KSIAM Annual Meeting is organized by Dabeen Lee. URL: https://www.ksiam.org/conference/84840fb6-87b0-4566-acc1-4802bde58fbd/welcome Date Nov 8, 2019 – Nov 9, 2019 Address: 61-13 Odongdo-ro, Sujeong-dong, Yeosu-si, Jeollanam-do (전남 여수시 오동도로 61-13) Venue Venezia Hotel & Resort Yeosu, Yeosu, Korea (여수 베네치아 호텔)  Address: 61-13 Odongdo-ro, Sujeong-dong, Yeosu-si, Jeollanam-do (전남 여수시 오동도로 61-13) Speakers Hyung-Chan An (안형찬), Yonsei University Tony Huynh, Monash University Dong Yeap Kang (강동엽),…

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Tony Huynh, Stable sets in graphs with bounded odd cycle packing number

November 12 Tuesday @ 4:30 PM - 5:30 PM
Room B232, IBS (기초과학연구원)

It is a classic result that the maximum weight stable set problem is efficiently solvable for bipartite graphs.  The recent bimodular algorithm of Artmann, Weismantel and Zenklusen shows that it is also efficiently solvable for graphs without two disjoint odd cycles.  The complexity of the stable set problem for graphs without $k$ disjoint odd cycles is a long-standing open problem for all other values of $k$.  We prove that under the additional assumption that the input graph is embedded in a…

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Ruth Luo, Induced Turán problems for hypergraphs

Speaker

Ruth Luo
University of California, San Diego
https://faculty.math.illinois.edu/~ruthluo2/
November 19 Tuesday @ 4:30 PM - 5:30 PM
Room B232, IBS (기초과학연구원)

Let $F$ be a graph. We say that a hypergraph $\mathcal H$ is an induced Berge $F$ if there exists a bijective mapping $f$ from the edges of $F$ to the hyperedges of $\mathcal H$ such that for all $xy \in E(F)$, $f(xy) \cap V(F) = \{x,y\}$. In this talk, we show asymptotics for the maximum number of edges in $r$-uniform hypergraphs with no induced Berge $F$. In particular, this function is strongly related to the generalized Turán function $ex(n,K_r, F)$, i.e., the…

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December 2019

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Jakub Gajarský, First-order interpretations of bounded expansion classes

December 10 Tuesday @ 4:30 PM - 5:30 PM
Room B232, IBS (기초과학연구원)

The notion of bounded expansion captures uniform sparsity of graph classes and renders various algorithmic problems that are hard in general tractable. In particular, the model-checking problem for first-order logic is fixed-parameter tractable over such graph classes. With the aim of generalizing such results to dense graphs, we introduce classes of graphs with structurally bounded expansion, defined as first-order interpretations of classes of bounded expansion. As a first step towards their algorithmic treatment, we provide their characterization analogous to the characterization of classes of bounded expansion via low…

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June 2020

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Seymour is Seventy

Monday, June 15, 2020 - Friday, June 19, 2020
ENS de Lyon, Lyon, France

A conference honouring the seventieth birthday of Paul Seymour To be held in ENS de Lyon, France, June 15 - 19, 2020 Conference Website: https://dimag.ibs.re.kr/seymour70/ Sponsors: IBS Discrete Mathematics Group. LIP, ENS de Lyon, France. Department of Mathematics, Princeton University.

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