Discrete Math Seminar

Name: David Wood, Proof of the Clustered Hadwiger Conjecture
Start: 2026-09-22T16:30:00+09:00
End: 2026-09-22T17:30:00+09:00
Location: Room B332

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		1 event 1 1 event, 1 4:30 PM - 5:30 PM Ben Lund, Incidences between points and n-flats in PG(n+d,q) September 1 Tuesday @ 4:30 PM - 5:30 PM KST Ben Lund, Incidences between points and n-flats in PG(n+d,q) Let $P$ be a set of points in $PG(n+d,q)$, and let $L$ be a set of $n$-flats. Here, $n$-flat is a short name for $n$-dimensional projective subspaces. A classical bound of Haemers, rediscovered in an influential paper of Vinh, gives an upper bound on the difference between the number of incidences between $P$ and $L$ … Continue Reading	0 events 2 0 events, 2	0 events 3 0 events, 3	0 events 4 0 events, 4	0 events 5 0 events, 5
0 events 6 0 events, 6	0 events 7 0 events, 7	1 event 8 1 event, 8 4:30 PM - 5:30 PM Olga Medrano Martín del Campo, Epsilon-saturation for Littlestone classes and stable graphs September 8 Tuesday @ 4:30 PM - 5:30 PM KST Olga Medrano Martín del Campo, Epsilon-saturation for Littlestone classes and stable graphs We introduce the concept of the saturation of a (bi)graph: the union closure after inductively adding its virtual elements, which are weighted ε-good (respectively ε-excellent sets) as in the Stable Regularity Lemma. In the Littlestone class and stable graph case, we show that if the saturation has bounded Littlestone dimension, then it is the smallest … Continue Reading	0 events 9 0 events, 9	0 events 10 0 events, 10	0 events 11 0 events, 11	0 events 12 0 events, 12
0 events 13 0 events, 13	0 events 14 0 events, 14	1 event 15 1 event, 15 4:30 PM - 5:30 PM Gabriëlle Zwaneveld, On Seymour-tight orientations September 15 Tuesday @ 4:30 PM - 5:30 PM KST Gabriëlle Zwaneveld, On Seymour-tight orientations I discuss 'almost counterexamples' to Seymour's second neighbourhood conjecture. In what we call Seymour-tight orientations, the size of the first neighbourhood of each vertex equals the size of its second neighbourhood. We give several examples and constructions. Specifically, we prove that the class of Seymour-tight orientations is closed under taking (generalized) lexicographic products. Moreover, the … Continue Reading	0 events 16 0 events, 16	0 events 17 0 events, 17	0 events 18 0 events, 18	0 events 19 0 events, 19
0 events 20 0 events, 20	0 events 21 0 events, 21	1 event 22 1 event, 22 4:30 PM - 5:30 PM David Wood, Proof of the Clustered Hadwiger Conjecture September 22 Tuesday @ 4:30 PM - 5:30 PM KST David Wood, Proof of the Clustered Hadwiger Conjecture Hadwiger famously conjectured that every $K_h$-minor-free graph is properly $(h-1)$-colourable. This talk will present the following improper analogue of Hadwiger's Conjecture: for fixed $h$, every $K_h$-minor-free graph is $(h-1)$-colourable with monochromatic components of bounded size. The number of colours is best possible regardless of the size of monochromatic components. This solves an open problem of … Continue Reading	0 events 23 0 events, 23	0 events 24 0 events, 24	0 events 25 0 events, 25	0 events 26 0 events, 26
0 events 27 0 events, 27	0 events 28 0 events, 28	0 events 29 0 events, 29	0 events 30 0 events, 30