Séminaire Lotharingien de Combinatoire, B83pref (2019), 1 p.

Christian Stump

Preface

The 83rd meeting of the Séminaire Lotharingien de Combinatoire took place from September 1 to 4, 2019, for the first time in the Evangelische Akademie in Bad Boll (Germany) at the foot of the Schwäbischen Alb.

Michael CUNTZ gave three lectures on "Weyl Groupoids", starting in rank 2 with freeze pattern and followed by a beautiful classification of crystallographic hyperplane arrangements, generalizing the classification of finite Weyl groups.

The second series of three lectures, "Counting Over Finite Fields and Shuffle Conjectures", was delivered by Anton Mellit on the shuffle theorem via very elegant counting of geometric objects over finite fields. He started with counting flags of vector spaces and proceeded with counting more and more involved structures to obtain a formula by Lascoux-Schützenberger for Kostka-Foulkes polynomials and of Haglund, Haiman, and Loehr for Macdonald polynomials.

The topics of the contributed talks were diverse as detailed in the list below, with multiple talks by young first-time participants.

We were (only) 30 participants in this new location but we very much enjoyed the atmosphere of the place, the pleasent surrounding and the sunny weather.

Contributed talks:

Bernhard BÖHMLER: Representation type and combinatorics

Theo DOUVROPOULOS: Coxeter factorizations and the matrix--tree theorem with generalized Jucys-Murphy weights

Gérard DUCHAMP: Non-commutative differential equations

Hans HÖNGESBERG: On a four-fold refined enumeration of alternating sign trapezoids

Alessandro IRACI: Refined Delta conjectures

Christian KRATTENTHALER: A joint central limit theorem for the sum-of-digits function, and asymptotic divisibility of Catalan-like sequences

René MARCZINZIK: Homological algebra and combinatorics

Vincel Hoang NGOC MINH: A family of Eulerian functions involved in regularization of divergent polyzetas

Philippe NADEAU: Divided symmetrization and quasisymmetric polynomials

Inês RODRIGUES: An action of the cactus group on shifted tableau crystals

Gerhard RÖHRLE: Freeness of multi-reflection arrangements

João Miguel SANTOS: Symplectic keys and Demazure atoms: a frank discussion}

Patrick WEGENER: Non-reduced reflection factorizations of Coxeter elements

List of Participants: