Proper conflict-free colourings of graphs
summary: Given a graph \(G\) of maximum degree \(\Delta\), the proper colouring problem asks for the minimum number of colours that can be assigned to the vertices of \(G\) such that no pair of adjacent vertices are given the same colour; it is easy to show that at most \(\Delta ...
Alternating and nondeterministic plane-walking automata
summary: Plane-walking automata were introduced by Salo & Törma to recognise languages of two-dimensional infinite words (subshifts), the counterpart of 4-way finite automata for two-dimensional finite words. We extend the model to allow for nondeterminism and alternation of quantifiers. We prove that the recognised subshifts form a strict subclass of sofic ...
On the complexity of computing tree-partitions
summary: Tree-partitions are graph decompositions that correspond to mapping vertices to nodes of a tree in such a way that adjacent vertices in the graph are either mapped to adjacent nodes of the tree or to the same node. The width of a tree-partition is the maximum number of vertices ...
À la lumière de quelques propriétés essentielles
Cet exposé consistera en quatre parties, chacune commençant par une introduction à un domaine de recherche et terminant par quelques contributions.
Nous débuterons par expliquer comment la conjecture polynomiale de Hales-Jewett à densité unifie plusieurs des généralisations du théorème de van der Waerden, ainsi que comment cette généralisation commune présente ...
On the intervals of framing lattices
summary: A flow graph \(G\) is an acyclic oriented graph with \(V(G) = [n]\), \(E(G)\) a multi-set of edges where each edge \((i,j)\) satisfies \(i<j\), and such that \(G\) has a unique source \(s=1\) and sink \(t=n\). On such a graph, a route is simply ...
On the Structure of Potential Counterexamples to the Borodin-Kostochka Conjecture
summary: The Borodin-Kostochka conjecture, a long-standing problem in graph theory, asserts that every graph \(G\) with maximum degree \(\Delta \geq 9\) satisfies \(\chi(G) \leq max \{\Delta - 1, \omega(G)\}\) where \(\chi(G)\) and \(\omega(G)\) are respectively the chromatic number and the clique number of \(G\). While the conjecture ...
Excluding a rectangular grid
summary: For every positive integer k, we define the k-treedepth as the largest graph parameter td_k satisfying (i) td_k(∅)=0; (ii) td_k(G) <= 1+ td_k(G-u) for every graph G and every vertex u; and (iii) if G is a (
Computability of Compact Spaces
summary: The topological properties of a set have a strong impact on its computability properties. A striking illustration of this idea is given by spheres, closed manifolds and finite graphs without endpoints : if a set X is homeomorphic to a sphere, a closed manifold or such a graph, then any ...
Classes de sous-shifts définis par des formules logiques.
summary: Une configuration est un coloriage du plan Z². Habituellement, les ensembles de configurations étudiés sont ceux définis par un ensemble de motifs "interdits" n'apparaissant dans aucune des configurations de l'ensemble. De tels ensembles sont appelés sous-shifts. Dans ce séminaire, on définit les ensembles de configurations grâce à ...
Manytamaris: on descriptions of the Tamari lattice
summary: Manytamaris is a website about the Tamari lattice. The interest in this particular lattice stems from its many properties, besides being a lattice, and its numerous appearances in different areas of mathematics. As such, the goal for Manytamaris is to be a survey on the descriptions of the Tamari ...
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