11 Juin - 17 Juin

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Mercredi 13 Juin
Heure: 14:00 - 15:00
Lieu: TBA (Institut Galilée)
Résumé: Network Interdiction
Description: Joe Naoum-Sawaya Network interdiction is a class of leader-follower optimization problem that seeks to identify network components to disrupt and inflict a maximum damage to a network. The objective of such models is to study the structural connectivity of the network in order to identify vulnerabilities. The application areas are diverse and include energy, telecommunication, and supply chain networks among others. This talk will review two particular variations of network interdiction: connectivity disruption and flow disruption. The connectivity disruption model identifies the nodes in a network whose disruption minimizes the maximum number of connected node pairs. The flow disruption model identifies the edges whose disruption minimizes the maximum flow between sources and destinations. We will present optimization models as well as solution approaches. We will particularly focus on the cases where uncertainty is present in the edge weights and propose customized solution approaches based on robust optimization, cutting planes, and Benders decomposition. The proposed cutting planes and Benders decomposition exploit the structure of the underlying optimization model and allows the modeling and the solution of general classes of uncertainty sets.
Jeudi 14 Juin
Heure: 12:15 - 13:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Deep Cooperative Reconstruction with Privacy Constraints
Description: Denis Maurel Nowadays, we can observe a multiplication of multi-view data in domains such as marketing, bank administration or even survey analysis. In this context, Machine Learning methods are used to analyze data from several heterogeneous sources (here called views) with the following problem: an individual described in some views might be missing in some other ones. This proliferation is accompanied by a global privacy awareness: one should never have access to data from all sources at once. To solve these problems, we propose a method called the Cooperative Reconstruction System (CRS) which aims at reconstructing missing individuals locally using information contained in external views without data transfer from a view to another.
Vendredi 15 Juin
Heure: 10:30 - 12:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Definable Ellipsoid Method, Sums-of-Squares Proofs, and the Graph Isomorphism Problem
Description: Joanna Ochremiak The isomorphisms between two graphs can be described by the solutions of a system of polynomial inequalities and equations. We analyse the relative power of different proof systems which can be used to certify that a system corresponding to a pair of non-isomorphic graphs has no solution. Our results complete a full cycle of implications to show that, for the graph isomorphism problem, the Sherali-Adams, Polynomial Calculus and Sums-of-Squares proof systems are equally powerful, up to a constant loss in the degree. We prove this statement purely about the relative strength of proof systems through an excursion into the descriptive complexity of the ellipsoid method and bounded-variable infinitary logics. This is joint work with Albert Atserias.