Seminars

GALaC organizes or participates in three different regular seminars.

GALaC team seminar

The GALaC team seminar is organized on a regular basis on Friday at 14:00 in the PCRI building (650) at LISN. Recent and up-coming seminars

Plateau Saclay Combinatorics Seminar

The Plateau Saclay Combinatorics Seminar is held on several Mondays at 11am in room Philippe Flajolet (top floor on the left) at LIX. It is co-organized by the Combi team of LIX and the GALaC team. The mailing list for this seminar is combi_lix_lri@services.cnrs.fr. Subscribe to this ...

Plateau Saclay Algorithms Seminar

The Plateau Saclay Algorithms Seminar is held every other Friday afternoon in LIX. This working group is partially supported by Labex DigiCosme (Digital worlds: distributed data, programs and architectures). If you do wish (or not) to receive any emails from this seminar, you can subscribe or unsubscribe from the mailing ...

Faster diameter computation in graphs of bounded Euler genus

-- Giannos Stamoulis (CNRS, IRIF)

Roditty and Vassilevska-Williams [STOC 2013] showed that computing the diameter, i.e., farthest distance between any two vertices, of an (unweighted, undirected) graph cannot be done in subquadratic time unless the Strong Exponential Time Hypothesis fails. In a breakthrough work, Cabello [TALG 2019] showed a subquadratic algorithm in planar graphs ...

Les méandres arcs-en-ciel sur des chemins de Dyck

-- Benjamin Dequêne (Université de Leeds)

Un méandre (de longueur n) est une paire de correspondences non-croisées sur {1,...,n}. On peut le représenter sur le plan réel comme un paire d'ensemble de demi-cercles, qui ne s'intersentent pas deux à deux, reliant n points sur une droite. Cette représentation géométrique permet d'introduire différentes ...

Lattice structures of Gog and Magog triangles

-- Ludovic Schwob (LIGM, Combi)

summary: Gog and Magog triangles are simple combinatorial objects which are equienumerated. Howewer, the problem of finding an explicit bijection between these has been an open problem since the 80’s. These are related to other interesting objects such as alternating sign matrices, plane partitions or aztec diamond tillings.
All ...

Non-intersecting paths and the determinant of the distance matrix of a tree

-- Mercedes Rosas (Universidad de Sevilla)

summary: We present a combinatorial proof of the Graham–Pollak formula for the determinant of the distance matrix of a tree, via sign-reversing involutions and the Lindström–Gessel–Viennot Lemma.
This is joint work with Emmanuel Briand, Luis Esquivias-Quintero, Álvaro Gutierrez, and Adrián Lillo.

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