Category: seminars

An introduction to twin-width in graphs via the study of highly inapproximable problems

-- Pierre Bergé (ISIMA, Université Clermont Auvergne)

summary: The goal of this seminar is to introduce the graph parameter "twin-width", defined by Bonnet et al. in 2020. The collection of graphs with bounded twin-width generalizes many well-known families of graphs : planar, bounded treewidth and cliquewidth, unit interval,... The first motivation behind this parameter was that FO-expressible NP-hard ...

TracInAD: Measuring Influence for Anomaly Detection

-- Hugo Thimonier (LISN, Galac)

summary: As with many other tasks, neural networks prove very effective for anomaly detection purposes. However, very few deep-learning models are suited for detecting anomalies on tabular datasets. This talk proposes a novel methodology to flag anomalies based on TracIn, an influence measure initially introduced for explicability purposes. The proposed ...

Intervalles linéaires dans les treillis de Dyck, Tamari et alt-Tamari.

-- Clément Cheneviere (Unistra)

Les treillis de Dyck et de Tamari sont des ordre partiels classiques sur les objets Catalan, et on peut notamment les définir sur les chemins de Dyck. Ces deux posets ne possèdent pas le même nombre d'intervalles, mais de façon surprenante, lorsque l'on ne regarde que leurs intervalles ...

Éléments minimaux des régions de Shi

-- Balthazar Charles (LISN, Galac)

summary: L'arrangement de Shi, introduit en 1987 par J.-Y. Shi, est un arrangement d'hyperplans liés aux groupes de réflexions cristallographiques possédant de nombreuses propriétés intéressantes. En particulier, les régions définies par les hyperplans liés à un groupe W correspondent aux états d'un automate introduit par B ...

Séminaire ouvert

-- Toute l'équipe (LIX, GALAC)

Lors d'un séminaire ouvert, le thème n'est pas décidé à l'avance. Tous les membres du séminaires sont invités à participer et peuvent proposer le jour même des interventions plus ou moins longues, des démos ou des questions ouvertes au reste de l'équipe.

(q,t)-symmetry in triangular partitions

-- Loïc Le Mogne (LISN, Galac)

summary: The study of Dyck paths and parking functions combinatorics is a central piece of the Diagonal Harmonic Polynomials theory. It is the origin of many currents problems of algebraic combinatorics. Interactioncs between Dyck paths, parking functions, the Tamari lattice, symmetric functions and other fields of mathematics or physics have ...

Designing truthful mecanism

-- Victor Glaser (LISN, Galac)

summary: In this presentation, we will focus on the generalization of knapsack budgeting. Given a set of projects and a budget, each voter selects a subset of projects; we want to maximize social welfare. Different measures can describe this (maximizing the minimum utility of the players, maximizing the sum of ...

Classification of truth revealing social choice algorithms

-- Valentin Dardilhac (LISN, Galac)

summary: The talk will be on the field of social choices. A group of players
want to choose a subset of a set of objects respecting some properties
(maximal weight of the subset, maximal amount of objects in the subset, ...). To do so, they vote and use a social choice ...

Block gluing in Hom shifts and path reconfiguration in graphs

-- Benjamin Hellouin de Menibus (LISN, Galac)

summary: We study some tilings spaces that are defined from graph homomorphisms, called Hom shifts. Compared to general tiling spaces, they look the same in every direction (invariance by rotation and symmetry) and many undecidable problems or questions in tiling spaces seem to become easier for these objects, using graph-theoretical ...

Acyclic colorings of graphs and the probabilistic method

-- Quentin Chuet (LISN, Galac)

summary: Graph colorings have been extensively studied for the past century, due to the richness of the theory and its numerous applications. Part of the current research focuses on constrained colorings, and how their properties differ from proper colorings. When we require that, in a proper coloring, no (even) cycle ...

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