# List of upcoming online seminars in discrete mathematics, combinatorics, and graph theory

Here is a list of upcoming online seminars in combinatorics, automatically generated from researchseminars.org and a few other calendars available in the iCal format. Please let me know if you find any interesting iCal feed / Google Calendar of the seminars.

You can also find a list of upcoming workshops, conferences, and schools.

Timezone: Korea (KST), UTC/GMT+9.

### February 2023

#### February 10

12:15 am – 2:00 am

by Cosmin Pohoata (IAS School of Math) as part of Copenhagen-Jerusalem Combinatorics Seminar

Interactive livestream: https://ucph-ku.zoom.us/j/69937085835?pwd=S3J6UjQ0eFVPOU1hRUdCMHRnYXozUT09
Abstract: TBA

#### February 14

4:30 pm – 5:30 pm

Title: Strengthening Hadwiger’s conjecture for 4- and 5-chromatic graphs
by Raphael Steiner (ETH Zürich) as part of IBS/KAIST Discrete Math Seminar

Lecture held in Room B232, IBS.
Abstract: TBA

#### February 15

4:30 pm – 5:30 pm
Robert Hickingbotham (Monash University)

Title: Treewidth, Circle Graphs and Circular Drawings
by Robert Hickingbotham (Monash University) as part of IBS Virtual Discrete Math Colloquium

Abstract: TBA

#### February 16

6:00 pm – 7:00 pm

We introduce the following submodular generalization of the Shortest Cycle problem. For a nonnegative monotone submodular cost function $f$ defined on the vertices (or, equivalently, the edges) of an undirected graph $G$, we seek for a cycle $C$ in $G$ of minimum cost $Opt=f(C)$. We construct an algorithm that, given an $n$-vertex graph $G$, parameter $ε > 0$, and the function $f$ represented by an oracle, in time $n^{O(\log 1/ε)}$ finds a cycle $C$ in $G$ with $f(C)\leq (1+ε)Opt$. This is in sharp contrast with the non-approximability of the closely related Monotone Submodular Shortest $(s,t)$-Path problem, which requires exponentially many queries to the oracle for finding an $n^{2/3-ε}$-approximation [Goel et al., FOCS 2009]. When the function $f$ is integer-valued, our algorithm yields that a cycle of cost $Opt$ can be found in time $n^{O(\log Opt)}$. In particular, for $Opt=n^{O(1)}$ this gives a quasipolynomial-time algorithm computing a cycle of minimum submodular cost.

Joint work with: Fedor V. Fomin, Tuukka Korhonen, Daniel Lokshtanov, and Giannos Stamoulis

#### February 17

12:15 am – 2:00 am

by Geunho Lim (University of California, Santa Barbara) as part of Copenhagen-Jerusalem Combinatorics Seminar

Interactive livestream: https://ucph-ku.zoom.us/j/69937085835?pwd=S3J6UjQ0eFVPOU1hRUdCMHRnYXozUT09
Abstract: TBA

#### February 21

4:30 pm – 5:30 pm

Title: Fixed-Parameter Tractability of Directed Multicut with Three Terminal Pairs Parametrised by the Size of the Cutset: Twin-Width Meets Flow-Augmentation
by Meike Hatzel (National Institute of Informatics) as part of IBS/KAIST Discrete Math Seminar

Lecture held in Room B232, IBS.
Abstract: TBA

#### February 22

5:00 pm – 6:00 pm
Daniel Altman (University of Oxford)

by Daniel Altman (University of Oxford) as part of IBS Virtual Discrete Math Colloquium

Abstract: TBA

#### February 24

12:15 am – 1:15 am

by Stephanie Mui (NYU Courant) as part of Copenhagen-Jerusalem Combinatorics Seminar

Interactive livestream: https://ucph-ku.zoom.us/j/69937085835?pwd=S3J6UjQ0eFVPOU1hRUdCMHRnYXozUT09
Abstract: TBA

1:20 am – 2:20 am

by Fabio Alejandro Calderón Mateus (Universidad Nacional de Colombia) as part of Copenhagen-Jerusalem Combinatorics Seminar

Interactive livestream: https://ucph-ku.zoom.us/j/69937085835?pwd=S3J6UjQ0eFVPOU1hRUdCMHRnYXozUT09
Abstract: TBA

#### February 28

4:30 pm – 5:30 pm

Title: Recent progress on the Union-closed conjecture and related
by Stijn Cambie (IBS Extremal Combinatorics and Probability Group) as part of IBS/KAIST Discrete Math Seminar

Lecture held in Room B232, IBS.
Abstract: TBA

### March 2023

#### March 2

6:00 pm – 7:00 pm

The //disjoint paths logic//, FOL+DP, is an extension of First Order Logic (FOL) with the extra atomic predicate dp$_k(x_1,y_1,\ldots,x_k,y_k),$ expressing the existence of internally vertex-disjoint paths between $x_i$ and $y_i,$ for $i\in \{1,\ldots, k\}$. This logic can express a wide variety of problems that escape the expressibility potential of FOL. We prove that for every minor-closed graph class, model-checking for FOL+DP can be done in quadratic time. We also introduce an extension of FOL+DP, namely the //scattered disjoint paths logic//, FOL+SDP, where we further consider the atomic predicate $s$-sdp$_k(x_1,y_1,\ldots,x_k,y_k),$ demanding that the disjoint paths are within distance bigger than some fixed value $s$. Using the same technique we prove that model-checking for FOL+SDP can be done in quadratic time on classes of graphs with bounded Euler genus.

Joint work with Petr Golovach and Dimitrios M. Thilikos

#### March 3

12:15 am – 2:00 am

by István Tomon (Umeå University) as part of Copenhagen-Jerusalem Combinatorics Seminar

Interactive livestream: https://ucph-ku.zoom.us/j/69937085835?pwd=S3J6UjQ0eFVPOU1hRUdCMHRnYXozUT09
Abstract: TBA

#### March 7

4:30 pm – 5:30 pm

by Eunjin Oh (POSTECH) as part of IBS/KAIST Discrete Math Seminar

Lecture held in Room B232, IBS.
Abstract: TBA

#### March 9

10:00 am – 11:00 am
Marcelo Sales (Emory University)

by Marcelo Sales (Emory University) as part of IBS Virtual Discrete Math Colloquium

Abstract: TBA

#### March 10

12:15 am – 2:00 am

by Meghana M. Reddy (ETH Zürich) as part of Copenhagen-Jerusalem Combinatorics Seminar

Interactive livestream: https://ucph-ku.zoom.us/j/69937085835?pwd=S3J6UjQ0eFVPOU1hRUdCMHRnYXozUT09
Abstract: TBA

#### March 17

12:15 am – 2:00 am

by Rosna Paul (Graz University of Technology) as part of Copenhagen-Jerusalem Combinatorics Seminar

Interactive livestream: https://ucph-ku.zoom.us/j/69937085835?pwd=S3J6UjQ0eFVPOU1hRUdCMHRnYXozUT09
Abstract: TBA

#### March 22

4:30 pm – 5:30 pm
Qizhong Lin (Fuzhou University)

by Qizhong Lin (Fuzhou University) as part of IBS Virtual Discrete Math Colloquium

Abstract: TBA

### April 2023

#### April 4

4:30 pm – 5:30 pm

Title: Configurations of boxes
by István Tomon (Umeå universitet) as part of IBS/KAIST Discrete Math Seminar

Lecture held in Room B232, IBS.
Abstract: TBA

#### April 6

10:00 am – 11:00 am
Jie Han (Beijing Institute of Technology)

by Jie Han (Beijing Institute of Technology) as part of IBS Virtual Discrete Math Colloquium

Abstract: TBA

### May 2023

#### May 9

4:30 pm – 5:30 pm

by Maria Chudnovsky (Princeton University) as part of IBS/KAIST Discrete Math Seminar