Florian Gut and Attila Joó, Large vertex-flames in uncountable digraphs
The local connectivity $ \kappa_D(r,v) $ from $ r $ to $ v $ is defined to be the maximal number of internally disjoint $r\rightarrow v $ paths in $ …
10 events found.
Virtual Discrete Math Colloquium
Events
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Zoom ID: 869 4632 6610 (ibsdimag)
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Stefan Weltge, Integer programs with bounded subdeterminants and two nonzeros per row
Room B232 IBS (기초과학연구원)We give a strongly polynomial-time algorithm for integer linear programs defined by integer coefficient matrices whose subdeterminants are bounded by a constant and that contain at most two nonzero entries …
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Maria Chudnovsky, Induced subgraphs and tree decompositions
Zoom ID: 869 4632 6610 (ibsdimag)Tree decompositions are a powerful tool in structural graph theory; they are traditionally used in the context of forbidden graph minors. Connecting tree decompositions and forbidden induced subgraphs has until …
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Petr Hliněný, Twin-width is linear in the poset width
Zoom ID: 869 4632 6610 (ibsdimag)Twin-width is a new parameter informally measuring how diverse are the neighbourhoods of the graph vertices, and it extends also to other binary relational structures, e.g. to digraphs and posets. It was introduced …
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Péter Pál Pach, The Alon-Jaeger-Tarsi conjecture via group ring identities
Zoom ID: 869 4632 6610 (ibsdimag)The Alon-Jaeger-Tarsi conjecture states that for any finite field $\mathbb{F}$ of size at least 4 and any nonsingular matrix $M$ over $\mathbb{F}$ there exists a vector $x$ such that neither …
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Paul Seymour, Polynomial bounds for chromatic number
Zoom ID: 869 4632 6610 (ibsdimag)The Gyárfás-Sumner conjecture says that for every forest $H$, there is a function $f$ such that the chromatic number $\chi(G)$ is at most $f(\omega(G))$ for every $H$-free graph $G$ ("$H$-free" means with …
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Martin Milanič, Tree Decompositions with Bounded Independence Number
Zoom ID: 869 4632 6610 (ibsdimag)The independence number of a tree decomposition $\mathcal{T}$ of a graph is the smallest integer $k$ such that each bag of $\mathcal{T}$ induces a subgraph with independence number at most …
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Sebastian Wiederrecht, Matching Minors in Bipartite Graphs
Zoom ID: 869 4632 6610 (ibsdimag)Matching minors are a specialisation of minors which preserves the existence and elementary structural properties of perfect matchings. They were first discovered as part of the study of the Pfaffian …
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Tuukka Korhonen, Fast FPT-Approximation of Branchwidth
Zoom ID: 869 4632 6610 (ibsdimag)Branchwidth determines how graphs, and more generally, arbitrary connectivity (basically symmetric and submodular) functions could be decomposed into a tree-like structure by specific cuts. We develop a general framework for …
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David Munhá Correia, Rainbow matchings
Zoom ID: 869 4632 6610 (ibsdimag)I will discuss various results for rainbow matching problems. In particular, I will introduce a ‘sampling trick’ which can be used to obtain short proofs of old results as well …