Recent Perspectives on Non-crossing Partitions through Algebra, Combinatorics, and Probability

Non-crossing partitions are combinatorial structures that have proven to be of significant importance, as they play a crucial role in several areas of mathematics. One of the first systematic studies of non-crossing partitions was conducted by G. Kreweras in the 1970s. Among other notable properties, non-crossing partitions are counted by the famous Catalan numbers. On their own, non-crossing partitions exhibit a rich combinatorial structure, making them fascinating objects of study.

Non-crossing partitions have well-defined properties, including recurrence relations, generating functions, and combinatorial interpretations, which enable researchers to explore their intricate arrangements and uncover hidden patterns. Furthermore, they have demonstrated deep connections with fields such as algebra, geometry, and probability. These interactions allow for the transfer of insights and techniques between areas, leading to a deeper understanding of each. This workshop aims to further develop these connections by creating a collaborative environment where recent developments in algebra, geometry, and probability can be explored, with a specific focus on the significant role played by the combinatorics of non-crossing partitions. Through this inclusive and interdisciplinary approach, the workshop seeks to facilitate knowledge exchange, encourage fruitful collaborations, and promote a deeper understanding of the subject.

The workshop includes research talks on recent developments in the applications of non-crossing partitions across various fields of mathematics, as well as three mini-courses by:

  • Emily Barnard (DePaul University)
  • Philippe Biane (Université Gustave-Eiffel)
  • Christian Stump (Ruhr-Universität Bochum).

The following speakers have confirmed their participation:
O. Arizmendi (CIMAT, Mexico), B. Baumeister,  (Univ. of Bielefeld, Germany), G. Dorpalen-Barry (Texas A&M Univ., US), T. Douvropoulos (Brandeis Univ., US), S. Fishel (Arizona State Univ., US), L. Foissy (Univ. of Littoral Côte d’Opale, France), L. Gagnon (York Univ., Canada), M. Josuat-Vergès (Univ. Paris Cité, France)K. Kalampogia-Evangelinou (Univ. of Athens, Greece), J. Kock (Univ. of Copenhagen, Denmark), C. Krattenthaler (Univ. of Vienna, Austria), F. Lehner (TU Graz, Austria), D. Perales Anaya (Texas A&M Univ., US), S. Pfannerer (Waterloo Univ., Canada), V. Pons (Paris-Saclay Univ.), N. Reading (NC State Univ., Raleigh, US), F. Schreier-Aigner (Univ. of Vienna), N. Tapia (WIAS, Germany), P.-L. Tseng (NYU Abu Dhabi, UAE).

Abstract of the lectures

Emily Barnard (DePaul University)
Lattice Theory of Noncrossing partitions and Noncrossing arc diagrams 
 
Abstract: In this series of lectures, we will explore the combinatorics of finite lattices, their connection to Coxeter-Catalan combinatorics, representation theory, and dynamics. We will pay special attention to the interplay between the lattice of non-crossing partitions and c-Cambrian lattices. 
My lectures will be self-contained. While some basic familiarity with posets will be helpful, I will not assume knowledge about lattices and their properties. We will begin with a survey of helpful definitions, useful theorems/tools, and classical constructions. Our second lecture will focus directly on the lattice theory of the weak order, c-Cambrian lattices, and non-crossing partitions.
Finally, we will end with very recent results and open questions, including connections to representation theory and dynamics.

 
Philippe Biane (Université Gustave-Eiffel)
Non-crossing partitions and combinatorics, from random matrices to free cumulants to parking functions
 
Abstract: In the first two lectures, I will define free cumulants using non-crossing partitions, and explain how this definition emerges naturally from the theory of random matrices and integration on unitary groups.  The Schur-Weyl duality between symmetric groups and unitary groups plays an important role. I will then explain the basics of free probability and how the combinatorics of non-crossing partitions and free cumulants allows to relate it to random matrix theory.

In the last lecture, I will take on another topic, the combinatorics of maximal chains in the non-crossing partition lattice, which relates non-crossing partitions, parking functions, and the Tamari lattice.

Christian Stump (Ruhr-Universität Bochum)
A three-lecture journey through noncrossing Cataland

Abstract: 
In this series of lectures, we will explore noncrossing partitions within the realm of finite reflection groups.
In the first lecture, I will introduce you to noncrossing partitions as reflection group elements, present how to visualize them as set partitions in the classical types ABCD, and present some counting formulas.
In the second and third lectures, we will discuss the noncrossing Cataland. We will see their incarnations as clusters in cluster algebras and as specific subword complexes, and also the noncrossing partition lattice and the Cambrian lattice. We conclude by also considering noncrossing Fuss-Cataland by extending our discussion from finite reflection groups to their associated Artin groups.

 

Coming soon.

Organizers

Name Affiliation
Adrian Celestino Rodriguez Technische Universität Graz
Kurusch Ebrahimi-Fard Norwegian University for Science and Technology
James Mingo Queen's University
Martin Rubey Technical University of Vienna
Eleni Tzanaki University of Crete
Yannic Vargas CUNEF University

Attendees

Name Affiliation
Octavio Arizmendi Echegaray Centro de Investigación en Matemáticas
Emily Barnard DePaul University
Barbara Baumeister Bielefeld University
Philippe Biane Université Gustave Eiffel
Marek Bożejko University of Wroclaw
Andrew Campbell Institute of Science and Technology Austria
Jacob Campbell University of Virginia
Danai Deligeorgaki KTH Royal Institute of Technology
Galen Dorpalen-Barry Texas A & M University
Theodosios Douvropoulos Brandeis University
Wiktor Ejsmont Wroclaw University of Science and Technology
Sergio Alejandro Fernandez de soto Guerrero Technische Universität Graz
Susanna Fishel Arizona State University
Loïc Foissy University of Littoral Côte d’Opale
Lucas Gagnon York University
Dylan Gawlak Queen's University
Thorsten Holm Leibniz University
Matthieu Josuat-Vergès Université Paris-Cité
Grant Kaduck Queen's University
Katerina Kalampogia-Evangelinou University of Athens
Martin Kalck University of Graz
Joachim Kock University Autonoma de Barcelona
Christian Krattenthaler University of Vienna
Alexander Lazar Free University of Brussels
Franz Lehner Technische Universität Graz
Jianrong Li University of Vienna
Matthias Müller Technische Universität Graz
Philippe Nadeau Institute Camille Jordan
Alexandru Nica University of Waterloo
Daniel Perales Anaya Texas A & M University
Stephan Pfannerer University of Waterloo
Viviane Pons Paris-Saclay University
Nathan Reading North Carolina State University
Jorge Luis Santos Silva Universidad Nacional Autónoma de México
Florian Schreier-Aigner University of Vienna
Nikoleta Sevastaki University of Crete
Roland Speicher University of Saarland
Christian Stump Ruhr-Universität Bochum
Nikolas Tapia Technical University Berlin
Pei-Lun Tseng New York University Abu Dhabi
Josue Vazquez-Becerra Centro de Investigacion en Matematicas
At a glance
Type:
Workshop
When:
Feb. 17, 2025 — Feb. 21, 2025
Where:
ESI Boltzmann Lecture Hall
Organizer(s):
Adrian Celestino Rodriguez (TU Graz)
Kurusch Ebrahimi-Fard (NTNU, Trondheim)
James Mingo (Queen's University)
Martin Rubey (TU Vienna)
Eleni Tzanaki (U of Crete)
Yannic Vargas (CUNEF U, Madrid)