Ajout du séminaire de Benjamin BERGOUGNOUX du 19/06/24 à 15H

seminar.md

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 Pour tout renseignement ou proposition de séminaire, merci de contacter [Cyril Pain-Barre](mailto:cyril.pain-barre@lis-lab.fr).
 
+### Mercredi 19 juin 2024 à 15h
+
++ Date & Heure : Mercredi 19 juin 2024 à 15h
+
++ Lieu :  Salle de réunion COALA, dans les locaux de l'équipe.
+
++ Orateur : Benjamin BERGOUGNOUX, Postdoc à l'université de Varsovie, Pologne
+
++ Information(s) diverse(s) : exposé en anglais
+
++ Titre : Neighborhood operator logics: efficient model checking in terms of width parameters
+
++ Résumé : In this talk, I will introduce the family of neighborhood operator (NEO) logics which are extensions of existential MSO with predicates
+  for querying neighborhoods of vertex sets.
+  NEO logics have interesting modeling powers and nice algorithmic applications for several width parameters such as tree-width.
+  NEO logics capture many important graphs problems such as Independent Set, Dominating Set and many of their variants.
+  Moreover, some NEO logics capture CNF-SAT via the signed incidence graphs!
+  We can capture more problems by considering various extensions of NEO logics.
+  For example, we can capture problems with global constraints such as Hamiltonian Cycle via the extension of NEO logics
+  with predicates for checking the connectivity/acyclicity of vertex sets.
+
+  In terms of algorithmic applications, NEO logics seem to be the perfect candidates for capturing many problems
+  that can be solved efficiently in terms of width parameters.
+
+  This is suggested by the following three results:
+
+  - For tree-width, the most powerful NEO logics can be model checked in single exponential time in terms of tree-width
+  as implied by a result of Michal Pilipczuk [MFCS 2011].
+
+  - Jan Dreier, Lars Jaffke and I proved that, for an extension of one NEO logic, we can obtain an efficient model-checking algorithm
+  in terms of several width parameters more general than tree-width such as clique-width, rank-width and mim-width [SODA 2023].
+
+  - Vera Checkan, Giannos Stamoulis and I are currently proving that some NEO logic can be solved in single exponential time and
+  polynomial space for tree-depth: the shallow restriction of tree-width.
+  This last result could be interesting in practice where space usage is crucial.
+  I will present these three results after a friendly introduction on width parameters.
+
+
 ### Mercredi 12 juin 2024 à 14h
 
 + Lieu : Salle de réunion COALA, dans les locaux de l'équipe.