GT
Seminars are given every Friday from 2:00 to 3:00 (usually in room 178, but not for the time being). You are welcome 10 minutes earlier for tea, coffee and cake.
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Next talks:
The online talks are available here : https://webconf.u-bordeaux.fr/b/mar-ef4-zed.
Vendredi 24 Octobre
Transducing Linear Decompositions of Tournaments
Bojanczyk and Pilipczuk proved a conjecture of Courcelle stating that, for every integer~$k$, there exists a monadic second-order (MSO) transduction~$\Phi_k$ which, given a graph~$G$ of treewidth~$k$, can non-deterministically produce a tree decomposition of width~$f(k)$. Intuitively, this result shows that witnesses of bounded treewidth can be constructed —not in the usual algorithmic sense— but through a process definable in MSO logic.
Lower Bounds for Induced-Universal Graphs
We give a series of new lower bounds on the minimum number of vertices required by a graph to contain every graph of a given family as induced subgraph. In particular, we show that this induced-universal graph for $n$-vertex planar graphs must have at least $10.52n$ vertices. We also show that the number of conflicting graphs to consider in order to beat this lower bound is at least~$137$.
Vendredi 08 Novembre ŕ 14h - Jedrzej Hodor
Planarity and dimension
There are various parameters used to measure the complexity of posets (partially ordered sets), and many intriguing questions arise when exploring the relationships between these parameters. Our focus is on the complexity of posets that can be drawn in the plane, analogous to planar graphs. The parameters we discuss include dimension, number of minimal elements, standard example number, and boolean dimension.

