BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Discrete Mathematics Group - ECPv5.15.0//NONSGML v1.0//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
X-WR-CALNAME:Discrete Mathematics Group
X-ORIGINAL-URL:https://dimag.ibs.re.kr
X-WR-CALDESC:Events for Discrete Mathematics Group
REFRESH-INTERVAL;VALUE=DURATION:PT1H
X-Robots-Tag:noindex
X-PUBLISHED-TTL:PT1H
BEGIN:VTIMEZONE
TZID:Asia/Seoul
BEGIN:STANDARD
TZOFFSETFROM:+0900
TZOFFSETTO:+0900
TZNAME:KST
DTSTART:20220101T000000
END:STANDARD
END:VTIMEZONE
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20220523T163000
DTEND;TZID=Asia/Seoul:20220523T173000
DTSTAMP:20220522T092234
CREATED:20220523T073000Z
LAST-MODIFIED:20220516T214605Z
UID:5451-1653323400-1653327000@dimag.ibs.re.kr
SUMMARY:Stijn Cambie\, The precise diameter of reconfiguration graphs
DESCRIPTION:Reconfiguration is about changing instances in small steps. For example\, one can perform certain moves on a Rubik’s cube\, each of them changing its configuration a bit. In this case\, in at most 20 steps\, one can end up with the preferred result. One could construct a graph with as nodes the possible configurations of the Rubik’s cube (up to some isomorphism) and connect two nodes if one can be obtained by applying only one move to the other. Finding an optimal solution\, i.e. a minimum number of moves to solve a Rubik’s cube is now equivalent to finding the distance in the graph. \nWe will wonder about similar problems in reconfiguration\, but applied to list- and DP-colouring. In this case\, the small step consists of recolouring precisely one vertex. Now we will be interested in the diameter of the reconfiguration graph and show that sometimes we can determine the precise diameters of these. \nAs such\, during this talk\, we present some main ideas of [arXiv:2204.07928].
URL:https://dimag.ibs.re.kr/event/2022-05-23/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20220525T163000
DTEND;TZID=Asia/Seoul:20220525T173000
DTSTAMP:20220522T092234
CREATED:20220525T073000Z
LAST-MODIFIED:20220518T041938Z
UID:5509-1653496200-1653499800@dimag.ibs.re.kr
SUMMARY:Sebastian Siebertz\, Transducing paths in graph classes with unbounded shrubdepth
DESCRIPTION:Transductions are a general formalism for expressing transformations of graphs (and more generally\, of relational structures) in logic. We prove that a graph class C can be FO-transduced from a class of bounded-height trees (that is\, has bounded shrubdepth) if\, and only if\, from C one cannot FO-transduce the class of all paths. This establishes one of the three remaining open questions posed by Blumensath and Courcelle about the MSO-transduction quasi-order\, even in the stronger form that concerns FO-transductions instead of MSO-transductions. \nThe backbone of our proof is a graph-theoretic statement that says the following: If a graph G excludes a path\, the bipartite complement of a path\, and a half-graph as semi-induced subgraphs\, then the vertex set of G can be partitioned into a bounded number of parts so that every part induces a cograph of bounded height\, and every pair of parts semi-induce a bi-cograph of bounded height. This statement may be of independent interest; for instance\, it implies that the graphs in question form a class that is linearly chi-bounded. \nThis is joint work with Patrice Ossona de Mendez and Michał Pilipczuk.
URL:https://dimag.ibs.re.kr/event/2022-05-25/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20220530T163000
DTEND;TZID=Asia/Seoul:20220530T173000
DTSTAMP:20220522T092234
CREATED:20220530T073000Z
LAST-MODIFIED:20220426T130212Z
UID:5495-1653928200-1653931800@dimag.ibs.re.kr
SUMMARY:Hongseok Yang (양홍석)\, TBA
DESCRIPTION:
URL:https://dimag.ibs.re.kr/event/2022-05-30/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20220602T103000
DTEND;TZID=Asia/Seoul:20220602T113000
DTSTAMP:20220522T092234
CREATED:20220602T013000Z
LAST-MODIFIED:20220506T045858Z
UID:5595-1654165800-1654169400@dimag.ibs.re.kr
SUMMARY:Jeck Lim\, Sums of linear transformations
DESCRIPTION:We show that if $L_1$ and $L_2$ are linear transformations from $\mathbb{Z}^d$ to $\mathbb{Z}^d$ satisfying certain mild conditions\, then\, for any finite subset $A$ of $\mathbb{Z}^d$\, \[ |L_1 A+L_2 A|\geq (|\det(L_1)|^{1/d}+|\det(L_2)|^{1/d})^d |A|- o(|A|).\] This result corrects and confirms the two-summand case of a conjecture of Bukh and is best possible up to the lower-order term for many choices of $L_1$ and $L_2$. As an application\, we prove a lower bound for $|A + \lambda \cdot A|$ when $A$ is a finite set of real numbers and $\lambda$ is an algebraic number.\nJoint work with David Conlon.
URL:https://dimag.ibs.re.kr/event/2022-06-02/
LOCATION:Zoom ID: 870 0312 9412 (ibsecopro)
CATEGORIES:Virtual Discrete Math Colloquium
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20220613T163000
DTEND;TZID=Asia/Seoul:20220613T173000
DTSTAMP:20220522T092234
CREATED:20220502T144707Z
LAST-MODIFIED:20220502T144707Z
UID:5578-1655137800-1655141400@dimag.ibs.re.kr
SUMMARY:Amadeus Reinald\, TBA
DESCRIPTION:
URL:https://dimag.ibs.re.kr/event/2022-06-13/
LOCATION:Room B332\, IBS (기초과학연구원)
CATEGORIES:Discrete Math Seminar
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=Asia/Seoul:20220720T163000
DTEND;TZID=Asia/Seoul:20220720T173000
DTSTAMP:20220522T092234
CREATED:20220512T003143Z
LAST-MODIFIED:20220512T003143Z
UID:5637-1658334600-1658338200@dimag.ibs.re.kr
SUMMARY:Lars Jaffke\, Taming graphs with no large creatures and skinny ladders
DESCRIPTION:We confirm a conjecture of Gartland and Lokshtanov [arXiv:2007.08761]: if for a hereditary graph class $\mathcal{G}$ there exists a constant $k$ such that no member of $\mathcal{G}$ contains a $k$-creature as an induced subgraph or a $k$-skinny-ladder as an induced minor\, then there exists a polynomial $p$ such that every $G \in \mathcal{G}$ contains at most $p(|V(G)|)$ minimal separators. By a result of Fomin\, Todinca\, and Villanger [SIAM J. Comput. 2015] the latter entails the existence of polynomial-time algorithms for Maximum Weight Independent Set\, Feedback Vertex Set and many other problems\, when restricted to an input graph from $\mathcal{G}$. Furthermore\, as shown by Gartland and Lokshtanov\, our result implies a full dichotomy of hereditary graph classes defined by a finite set of forbidden induced subgraphs into tame (admitting a polynomial bound of the number of minimal separators) and feral (containing infinitely many graphs with exponential number of minimal separators). \nJoint work with Jakub Gajarský\, Paloma T. Lima\, Jana Novotná\, Marcin Pilipczuk\, Paweł Rzążewski\, and Uéverton S. Souza.
URL:https://dimag.ibs.re.kr/event/2022-07-20/
LOCATION:Zoom ID: 869 4632 6610 (ibsdimag)
CATEGORIES:Virtual Discrete Math Colloquium
END:VEVENT
END:VCALENDAR