NoyFest

24 April 2026, FME, Barcelona, Catalunya

Workshop to recognize the scientific trajectory of Marc Noy, organised by the research group GAPCOMB at UPC.

Location: Sala d'actes, FME, Barcelona, Catalunya.

Registration: registration is free but mandatory, please fill in this form before 17th April.

Schedule: 

Talks:

Michael Drmota (TU Wien): Universality in the enumeration of planar maps and graphs

Abstract: It is a remarkable fact that the "structure" of the formulas for the asymptotic enumeration of several classes of planar graphs and planar maps has a universal form  $const. \rho^n n^{-5/2}$ or $const. \rho^n n^{-7/2}$ depending whether we are considering vertex labelled or unlabelled versions. Marc Noy has contributed substantially to these kinds of results. The purpose of this talk is to give an overview and background on such results including some recent developments.

Vlady Ravelomana (IRIF & Univ. Paris): Working with Marc

Abstract: I have known Pr. Marc Noy since the early 2000s, and over the years our research paths have crossed several times, particularly in the field of random graphs. In this talk, I will briefly recount some of these adventures — the problems we tackled or not — and describe some of these journeys that ultimately brought us together in fruitful collaborations but not only.

Éric Fusy (CNRS & LIGM): Enumeration of k-connected planar triangulations

Abstract: The enumeration of k-connected rooted planar triangulations can be considered for any fixed k from 1 to 5. It goes back to Tutte (for k<=4) who introduced two generating function methods: (i) solving a functional equation (with a catalytic variable) obtained by root-deletion, such equations being easier to obtain for lower k, or (ii) using a substitution approach by extraction of a core in order to relate the generating functions of k-connected and of (k-1)-connected rooted planar triangulations, making it possible to solve the former from the latter (or conversely). The catalytic approach was also applied by Brown (k=3) and Mullin (k=2); and the substitution approach was extended by Gao, Wanless and Wormald to solve the case k=5, which requires a bivariate extension. After recalling these results, I will show a parallel between the core-extraction approach and the bijective method based on outdegree-constrained orientations, where the orientations for the k-connected case can be deduced from the ones for the (k-1)-connected case.

Based on joint work with Olivier Bernardi and Shizhe Liang

Andrew Goodall (IUUK, Charles University Prague): On the irreducibility of Tutte polynomials of ranked sets

Abstract: A quarter of a century ago Merino, de Mier and Noy showed that a matroid M is connected if and only if its Tutte polynomial T(M;x,y) is irreducible as a bivariate polynomial over a field of characteristic zero. (Crapo's other characterization - that the coefficient of x is non-zero - is an ingredient in the proof.) In the form of its subset expansion, the Tutte polynomial can be defined for any set E with an integer-valued rank function r satisfying the minimal conditions that r is subcardinal and takes its maximum value on E. By leveraging the recently shown equivalence (Beke, Csaji, Csikvari, Pituk) between Brylawski's coefficient relations and the simplification of the Tutte polynomial along the hyperbola (x-1)(y-1)=1, we obtain a streamlined proof of the original result for matroids which moreover applies to a more general class of ranked sets.

This is joint work with  Florent Jouve and Jean-Sébastien Sereni.

Élie de Panafieu (Nokia Bell Labs):  Analysis of two algorithms: voting and clustering 

Abstract:  I will present two topics I had the pleasure of working on with Marc and several co-authors. The first concerns the probability of existence of a candidate preferred by a majority of voters to any other. The second is related to the parametrization of clustering algorithms and its link with Erdős-Rényi graphs conditioned on every component being a clique.

Colin McDiarmid (Oxford): Random graphs from a structured class

Abstract: The class of forests and the class of planar graphs are examples of `structured’ classes.  We consider random graphs R_n sampled uniformly from the n-vertex graphs in a suitable general structured class.  We see that we can learn about the behaviour of R_n for large n, though our general results are much less precise than known results about specific classes, by Marc Noy and others.

Anusch Taraz (TUUH Hamburg): On limiting probabilities and almost monochromatic structures

Abstract: In this talk we will first survey results in the area of logical limit laws that have their roots in joint work with Marc  when he was visiting TU München as Humboldt Research Awardee and John von Neumann Professor.  In the second half, I will take a step forward and suggest a novel Ramsey variant as a new sphere of activity - for Marc and, of course, everybody else. 

Oriol Serra (UPC): Marc Noy, colleague and friend

Abstract: This will be an informal talk collecting some highlights about Marc mostly biassed by personal memories of a longstanding friendship and professional collaboration.

Local Organising Committee (UPC):

Anna de Mier, Guillem Perarnau, Juanjo Rué, Oriol Serra.

The event is sponsored by the grant COCOA: COntemporary COmbinatorics and its Applications (PID2023-147202NB-I00)