Clément Legrand – Duchesne

IRIF clement.legrand-duchesne@irif.fr

I am associate professor (maître de conférences) at IRIF since September 2026. I am broadly interested in combinatorics and graph theory, with a special fondness for reconfiguration and problems with a geometric flavor. In particular, a significant part of my work focuses on colorings and Kempe changes.

Previously, I completed my PhD in July 2024 at LaBRI in Bordeaux under the supervision of Marthe Bonamy and Vincent Delecroix. My manuscript is accessible here. I was then a postdoctoral researcher at Jagiellonian university from 2024 to 2026, with Bartosz Walczak and Piotr Micek.

Publications

Workshops and Talks

  • Journées CALAMAR (June 11, 2026): The container method (slides, video)
  • Dirac's theorem and the switch geometry of perfect matchings:
    • Combinatorics and Interaction seminar of Krakow's Institute of Mathematics of the Polish Academy of Sciences (June 2, 2026)
    • Jagiellonian Theoretical Computer Science seminar (April 29, 2026)
    • Nice Graph seminar (January 14, 2026)
    • Marseille Graph seminar (LIS, January 12, 2026)
    • Clermont-Ferrand Graph seminar (January 8, 2026)
    • Grenoble Graph seminar (January 6, 2026)
    • Lyon Graph seminar (November 13, 2025)
  • Reconfiguration of square-tiled surfaces:
    • Marseille Geometry seminar (I2M, January 16, 2026)
    • Invited speaker at Journées de Combinatoire de Bordeaux 2024 (February 6, 2024)
    • Luxembourg Geometry seminar (November 13, 2023)
    • Bordeaux Combinatorics seminar (October 23, 2023)
    • Warwick Geometry and topology seminar (October 19, 2023)
  • Recoloring odd-hole free graphs:
    • Delft Discrete Mathematics and Optimization seminar (October 16, 2025)
    • Bremen Workshop on Combinatorial Reconfiguration and Beyond (November 28, 2024)
    • Polish Combinatorial Conference (September 19, 2024)
  • Random spread-embedding of bounded degree trees:
    • Amsterdam graph theory seminar (October 14, 2025)
    • 10th CCGT (September 22, 2025)
    • Bordeaux Graph seminar (January 19, 2023)
    • Lyon Graph seminar (December 12, 2023)
    • Grenoble Graph seminar (December 7, 2023)
    • Journées Graphes et Algorithmique 2023 (November 22, 2023)
  • Introductory lecture on geometric reconfiguration: Triangulations and knots. (Master course at TU Berlin. November 27, 2024)
  • A Gray code for directed spanning trees of tournaments:
    • Journées Graphes et Algorithmiques 2024 (November 19, 2024)
  • Kempe recoloring of sparse graphs (video):
    • Jagiellonian Theoretical Computer Science seminar (October 23, 2024)
  • Order and Geometry (September 2024)
  • Workshop in Edinburgh: Early Career Researchers in Combinatorics (July 2024)
  • Invited speaker at Journées CALAMAR (January 16, 2024): Online edge coloring (slides, video)
  • The structure of minor-free quasi-transitive graphs:
    • Bratislava Algebraic Graph Theory seminar (May 24, 2024)
    • Delft Discrete Mathematics and Optimization seminar (November 10, 2023)
    • UCL Cominatorics seminar (October 16, 2023)
    • Bordeaux Graph seminar (October 13, 2023)
  • Recoloring version of Hadwiger's conjecture:
    • Amsterdam combinatorics and probability seminar (October 31, 2023)
    • Eurocomb23 (upcoming)
    • Oxford combinatorial theory seminar (February 1, 2022)
    • LSE combinatorics seminar (December 3, 2021)
    • JGA 2021 (November 18, 2021)
    • Bordeaux Graph seminar (October 15, 2021)
  • Strengthening a theorem of Meyniel:
    • JGA 2022 (November 2022)
    • Bordeaux Graph seminar (November 25, 2022)
    • Journées ANR GrR (June 2022)
  • Parametrized complexity of untangling knots:
    • LaBRI's Junior seminar (October 26, 2022)
    • ICALP 2022
  • Kempe changes in bounded treewidth graphs: Eurocomb 2021
  • Sparse Graph Coalition Workshop on Reconfiguration (May 2021)
  • Kempe changes on \(\Delta\)-colorings: Workshop on Combinatorial Reconfiguration at ICALP 2021
  • Journées ANR GrR (June 2021)

Teaching

  • Random stuff on graphs: Probabilistic method and randomized algorithms (Master at Jagiellonian University), 2026.
  • Networks (First year of IUT), 2024
  • Human computer interaction in C# (Second year of IUT), 2024
  • Office hours (First year of IUT), 2024
  • Two lectures in the Master 2 Graph theory course: treewidth and graph minors, 2023
  • Algorithms on trees and functional programming (Second year of Bachelor degree), 2023
  • Combinatorics and probabilities (Second year of Bachelor degree), 2022
  • Introduction to computer science (First year of Bachelor degree), 2021
  • Colles en MP* et MPSI (weekly oral exams in mathematics) at Lycée du Parc, 2020

Interests

I practice bouldering and rock climbing several times a week and I play ultimate frisbee. I enjoy cross-country unicycle and board sports of all kinds. When the weather is not good enough for those activities, I like to read sci-fi or fantasy, to cook or to play classical guitar.