Manuel Lafond, Recognizing k-leaf powers in polynomial time, for constant k
Zoom ID: 869 4632 6610 (ibsdimag)A graph G is a k-leaf power if there exists a tree T whose leaf set is V(G), and such that uv is an edge if and only if the …
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Virtual Discrete Math Colloquium
Fedor Fomin, Long cycles in graphs: Extremal Combinatorics meets Parameterized Algorithms
Zoom ID: 869 4632 6610 (ibsdimag)We examine algorithmic extensions of two classic results of extremal combinatorics. First, the theorem of Dirac from 1952 asserts that a 2-connected graph G with the minimum vertex degree d>1, …
Jean-Florent Raymond, Long induced paths in minor-closed graph classes and beyond
Zoom ID: 869 4632 6610 (ibsdimag)In 1982 Galvin, Rival, and Sands proved that in $K_{t,t}$-subgraph free graphs (t being fixed), the existence of a path of order n guarantees the existence of an induced path …
Jakub Gajarský, Model Checking on Interpretations of Classes of Bounded Local Clique-Width
Zoom ID: 869 4632 6610 (ibsdimag)The first-order model checking problem for finite graphs asks, given a graph G and a first-order sentence $\phi$ as input, to decide whether $\phi$ holds on G. Showing the existence …
Michael Savery, Induced subgraphs of induced subgraphs of large chromatic number
Zoom ID: 869 4632 6610 (ibsdimag)We prove that for every graph F with at least one edge there are graphs H of arbitrarily large chromatic number and the same clique number as F such that …
Jan Kurkofka, Canonical Graph Decompositions via Coverings
Zoom ID: 869 4632 6610 (ibsdimag)We present a canonical way to decompose finite graphs into highly connected local parts. The decomposition depends only on an integer parameter whose choice sets the intended degree of locality. …
Sebastian Siebertz, Transducing paths in graph classes with unbounded shrubdepth
Zoom ID: 869 4632 6610 (ibsdimag)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 …
Jeck Lim, Sums of linear transformations
Zoom ID: 870 0312 9412 (ibsecopro) [CLOSED]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 $\mathbb{Z}^d$, \ This result corrects …
Chengfei Xie, On the packing densities of superballs in high dimensions
Zoom ID: 870 0312 9412 (ibsecopro) [CLOSED]The sphere packing problem asks for the densest packing of nonoverlapping equal-sized balls in the space. This is an old and difficult problem in discrete geometry. In this talk, we …
Xizhi Liu, Hypergraph Turán problem: from 1 to ∞
Zoom ID: 870 0312 9412 (ibsecopro) [CLOSED]One interesting difference between (nondegenerate) Graph Turán problem and Hypergraph Turán problem is that the hypergraph families can have at least two very different extremal constructions. In this talk, we …