Jérémy Cohen is a CNRS researcher affected to CREATIS, team Myriad since 2022. Before that, he was affected to IRISA, Rennes. He works on low-rank factorizations in data mining, with a strong focus on tensor decompositions, nonnegative matrix factorization, dictionary-based representations, data fusion and numerical optimization. He was previously a post-doctoral researcher at the University of Mons, Belgium. From 2013 to 2016, he was a PhD student under the supervision of Pierre Comon at Gipsa-lab, Grenoble.
He studied at Ecole Centrale de Lyon from 2010 to 2013 with major in Mathematical engineering, with double degrees in Mathematics (bachelor) and Telecommunications (master with INSA Lyon).

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Talk by: Théo Pierron (LIRIS)

Graph coloring is one of the most studied problems in graph theory. It originated in the 19th century with a well-known question: are four colors sufficient to color differently regions sharing a same border? About a century later, the question was finally solved by the so-called Four Color Theorem. At the core of its proof is a powerful tool, named the « discharging method », whose major downside is that it often requires lengthy case analyses. For the Four Color Theorem, this analysis is given to a computer for verification. This provided one of the first occurrences of a computer assisted proof.

Nowadays, using computers is more common to obtain some proofs, especially to deal with large verifications. However, it is still quite uncommon for a computer to actively look for a proof. We present here a Linear Programming approach to automatically look for a discharging proof and apply it to make some progress towards Wegner’s conjecture for distance-2 coloring of planar graphs. More precisely, we show that 12 colors are sufficient to color at distance 2 every planar graph with maximum degree 4.

Speaker bio:
After studying at ENS Rennes, Théo Pierron did a PhD at LaBRI in Bordeaux. He then went to Masaryk University (Brno, CZ) for a one-year postdoc before being hired as associate professor at LIRIS in 2020. His work involves graph theory and algorithmics. Hde is also interested in most areas of discrete mathematics.