Previous talks, of the year and of the previous ones: see the slidebar Talks at the right hand side.
Coming talks: (scheduled on Mondays from 9:30 to 10:30 (or during the slot of the GT if there is no GT) for the Petite École de Combinatoire and from 10:45 to 11:45 for the workgroup, in room 076 by default)
Contact the secretary if you want to propose a talk or to receive announcements.
Calendrier universitaire (des licences) : https://www.u-bordeaux.fr/content/download/75551/583982/version/4/file/Calendrier_Licence_2018-2019.pdf


2019-2020


Lundi 23 septembre : de 9h30 à 10h30 : (Petite école de combinatoire) : Andrew Elvey Price

Titre : Elliptic functions in enumerative combinatorics (1)

Résumé : Elliptic functions have a rich history in mathematical disciplines ranging from number theory to complex analysis to integrable models in physics. In recent years, a number of problems in enumerative combinatorics have been exactly solved in terms of some sort of elliptic functions, for example: - Certain quadrant walk models (Bernadi, Bousquet-Mélou and Raschel) - Enumeration of square lattice paths by winding angle (Budd) - Weighted Eulerian orientations on planar maps (Bousquet-Mélou, E.P. and Zinn-Justin, following Kostov). I will describe a unified framework to solve these problems and more using Jacobi elliptic theta functions. Such solutions are fairly convenient as they allow terms of the sequence to be rapidly computed and also generally yield precise asymptotic and algebraic information about the original series.

In the first part I will describe some fundamental properties of theta functions, and the relevance of some of these properties in the combinatorial setting. As a simple example, I will then show a way to solve a particular quadrant walk model known as Kreweras walks using theta functions. Finally, I will describe some slightly more complicated examples that can be solved using this method, and which can't obviously be solved in a simpler way.

Part 1: Introduction to Jacobi theta functions - analytic and algebraic properties

Part 2: Solution to Kreweras walks in terms of Jacobi theta functions

Part 3: Generalisations and further examples


Lundi 23 septembre :

Élise Goujard (IMB) https://sites.google.com/site/elisegoujard/

Titre :Surfaces à petits carreaux, cartes métriques, et volumes de Masur-Veech

Résumé : Les surfaces à petits carreaux sont des objets géométriques et combinatoires obtenus en recollant des carrés le long des côtés. Ces surfaces sont naturellement munies d'une métrique plate à singularités coniques, et correspondent à des points "entiers" dans l'espace de module des surfaces plates. Le comptage de ces surfaces, pour certains types combinatoires fixés, permet donc d'évaluer le volume de Masur-Veech de ces espaces de modules. Dans un travail joint avec Vincent Delecroix, Peter Zograf, Anton Zorich, nous donnons une formule pour ces volumes, ainsi que plusieurs conjectures concernant les surfaces à petits carreaux en genre grand. Le comptage des surfaces à petits carreaux est effectué à l'aide du comptage des métriques entières sur les cartes combinatoires naturellement associées à ces surfaces.


Lundi 30 septembre :

Andrew Elvey Price : PÉC : Titre : 'Elliptic functions in enumerative combinatorics (2)

Résumé : Elliptic functions have a rich history in mathematical disciplines ranging from number theory to complex analysis to integrable models in physics. In recent years, a number of problems in enumerative combinatorics have been exactly solved in terms of some sort of elliptic functions, for example: - Certain quadrant walk models (Bernadi, Bousquet-Mélou and Raschel) - Enumeration of square lattice paths by winding angle (Budd) - Weighted Eulerian orientations on planar maps (Bousquet-Mélou, E.P. and Zinn-Justin, following Kostov). I will describe a unified framework to solve these problems and more using Jacobi elliptic theta functions. Such solutions are fairly convenient as they allow terms of the sequence to be rapidly computed and also generally yield precise asymptotic and algebraic information about the original series.

In the first part I will describe some fundamental properties of theta functions, and the relevance of some of these properties in the combinatorial setting. As a simple example, I will then show a way to solve a particular quadrant walk model known as Kreweras walks using theta functions. Finally, I will describe some slightly more complicated examples that can be solved using this method, and which can't obviously be solved in a simpler way.

Part 1: Introduction to Jacobi theta functions - analytic and algebraic properties

Part 2: Solution to Kreweras walks in terms of Jacobi theta functions

Part 3: Generalisations and further examples

Peter McNamara https://www.linux.bucknell.edu/~pm040/index.html

Titre : .../...

Résumé : .../...


Lundi 7 octobre : '

Andrew Elvey Price : PÉC : Titre : 'Elliptic functions in enumerative combinatorics (3)

Résumé : Elliptic functions have a rich history in mathematical disciplines ranging from number theory to complex analysis to integrable models in physics. In recent years, a number of problems in enumerative combinatorics have been exactly solved in terms of some sort of elliptic functions, for example: - Certain quadrant walk models (Bernadi, Bousquet-Mélou and Raschel) - Enumeration of square lattice paths by winding angle (Budd) - Weighted Eulerian orientations on planar maps (Bousquet-Mélou, E.P. and Zinn-Justin, following Kostov). I will describe a unified framework to solve these problems and more using Jacobi elliptic theta functions. Such solutions are fairly convenient as they allow terms of the sequence to be rapidly computed and also generally yield precise asymptotic and algebraic information about the original series.

In the first part I will describe some fundamental properties of theta functions, and the relevance of some of these properties in the combinatorial setting. As a simple example, I will then show a way to solve a particular quadrant walk model known as Kreweras walks using theta functions. Finally, I will describe some slightly more complicated examples that can be solved using this method, and which can't obviously be solved in a simpler way.

Part 1: Introduction to Jacobi theta functions - analytic and algebraic properties

Part 2: Solution to Kreweras walks in terms of Jacobi theta functions

Part 3: Generalisations and further examples

Jean-François Marckert

Titre : The combinatorics of the colliding bullets

Résumé : The finite colliding bullets problem is the following simple problem: consider a gun, whose barrel remains in a fixed direction; let (Vi)1≤ i≤ n be an i.i.d. family of random variables with uniform distribution on [0,1]; shoot n bullets one after another at times 1,2,..., n, where the ith bullet has speed Vi. When two bullets collide, they both annihilate. We give the distribution of the number of surviving bullets, and in some generalisation of this model. While the distribution is relatively simple, the proof is surprisingly intricate and mixes combinatorial and geometric arguments (Common work with Nicolas Broutin).

à saisir !

02/09/2019 en 178 car colloque/workshop

28/10/2019 en 178 car 076 pour le colloque BGW

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Muriel Livernet (Université Paris Diderot) https://webusers.imj-prg.fr/~muriel.livernet/ AÀP

Titre : Questions combinatoires ouvertes en topologie algébrique au travers des opérades

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Pascal Weil

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invité de Neuchatel d'Adrian Tanasa et Pascal Weil


Raoul Santachiara (Laboratoire de Physique Théorique et Modèles Statistiques, Université Paris-Sud (Paris-Saclay)) http://lptms.u-psud.fr/raoul_santachiara/ : à confirmer


Vincent Rivasseau (Université Paris-Sud (Paris-Saclay)) https://en.wikipedia.org/wiki/Vincent_Rivasseau

à confirmer (demande AAP 2018)


Iain Moffatt (Royal Holloway (université de Londres), Royaume-Uni) http://www.personal.rhul.ac.uk/uxah/001/

à confirmer (demande AAP 2018)


Laurent Vuillon (LAboratoire de MAthématiques (LAMA), Université Savoie Mont Blanc) http://www.lama.univ-savoie.fr/~vuillon/

Titre : version combinatoire des mots de la conjecture de Frobenius sur les nombres de Markoff [travaux récents avec C. Reutenauer]

Résumé :


Historique du Groupe de Travail et de Petite École de Combinatoire


Calendrier universitaire : https://www.u-bordeaux.fr/Profils/Etudiant/College-Sciences-et-technologies2/Calendrier-examens http://www.u-bordeaux.fr/Actualites/De-la-formation/Dates-de-rentree-a-vos-agendas http://www.u-bordeaux.fr/content/download/61593/461612/version/1/file/Calendrier%20rentr%C3%A9e%20ST_%20Licence%202018-2019.pdf

Jours fériés (susceptibles de concerner un vendredi) : 1er novembre, 11 novembre, 25 décembre, 1er janvier, 1er mai, 8 mai, jeudi de l'Ascension (vers la mi-mai)

Colloque annuel ALEA (vers fin mars) ! 78th Séminaire Lotharingien de combinatoire, Ottrott March 26 - 29 2017, ThibonFest

Friday, jj(th) mmmm: ...

Title: ...

Abstract: ...

plan tranches 1&2 http://www.pmwiki.org/wiki/PmWiki/Characters

Envoyez un courriel au secrétaire (Olivier Guibert) du Groupe de Travail si vous avez un exposé à présenter.

JCB 2015

journées ALÉA du ... au .../.../2015


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