Séminaire Lotharingien de Combinatoire, B92pref (2024), 1 p.

Christian Krattenthaler

Preface

The 92nd Meeting of the Séminaire Lotharingien de Combinatoire took place from September 15 to 18, 2024, in the Bundesinstitut für Erwachsenenbildung (BIFEB) in Strobl (Austria).

The weather forecast promised heavy and continuous rain for the weekend before the meeting (including Monday and Tuesday). As I learned that was presented as apocalypse in German newspapers and the urgent advice was to stay outside of Austria during that period. Since for those who looked into these forecasts in more detail the predictions of the apocalypse were a bit exaggerated and imprecise, I sent an email to the participants, explaining that, yes, there will be serious rain fall, but the areas in danger of desaster would lie somewhere else (namely in the northwest of Vienna), and moreover rain will pause in the night from Saturday to Sunday. The email ended by: "... So I do not expect any major problems, except that the weather will not be ideal for swimming in the lake ..."

It turned out that I was - more or less - right. The participants who did not come from Vienna did not have the slightest problem to reach Strobl (except for the usual delays on Deutsche Bahn). On the other hand, going from Vienna to Strobl on that Sunday became an adventure. As we learned later, Vienna and the Vienna area had never seen so much rain over the past 150 years (the timespan for which records exist). The "river" Wien (which is usually a trickle) became indeed a river and spilled over. As a consequence of this and similar spillovers most underground lines did not run. The trainline from Vienna to the west was already interrupted in the morning (in the Tulln area), and the same applied to the trainline to the south starting somewhere in the afternoon (in the Semmering area). Leaving Vienna by car was also a challenge because of local floodings in Vienna. Only Theresia Eisenkölbl realised soon enough that the only option was to go to the south (when this was still possible) and arrived in Strobl safely late in the evening. All other participants from Vienna (including those who flew to Vienna from abroad) stayed caught in Vienna.

Since leaving Vienna by public transport was impossible, the next day (= Monday) the only solution was to take an Uber to Linz, and from there train and bus to Strobl. Indeed, that worked smoothly (even though several euros had to be spent for this ...). Moreover, one participant took several people with his car. In the end, everybody made it to the BIFEB with only one exception, and the programme started with a delay of two and a half hours.

Long story short: The problems were not major enough to prevent us from having a very enjoyable 92nd Séminaire Lotharingien de Combinatoire.

The main lectures were this time given by Michele D'Adderio (Università di Pisa) and Jehanne Dousse (Université de Genève). D'Adderio's topic was "Sandpiles in q,t-Combinatorics". In his wonderful and enlightening lectures, he explained us his view of q,t-combinatorics, the beautiful combinatorics arising from Macdonald polynomials, the basics of the classical sandpile model, and what the two have to do with each other. On the other hand, Jehanne Dousse, in her lectures on "Integer Partitions and Perfect Crystals", carefully introduced us into a technically difficult subject, namely the theory of crystal graphs, which has extremely strong consequences in and mutual interactions with several different areas, in particular so with the area of partition identities.

As usual, the contributed talks (see the detailed list below) covered a variety of different topics, including rational Catalan combinatorics, Coxeter combinatorics, theory of integer partitions, partition congruences, combinatorics of representation theory of quivers, and matroid theory.

Coming back to the weather situation: on Monday it was miserable, with continuous rain. However, ironically, on Tuesday and on Wednesday the Wolfgangsee area presented itself from its best side: sunny and warm.