Sparse Graphs Coalition

Digraph structure theory has known several exciting developments recently. We propose to learn and work on topics around the directed flat wall theorem. In particular, there will be introductory talks to butterfly minors, directed tree-width, the directed grid-theorem and the directed flat wall theorem. We shall also explore links and extensions of these (matching theory, tournaments immersion, strong minors).

The workshop is intended to last one week (five workdays), starting on a Monday with two talks, an open-problem session, and the formation of groups. A typical day after Monday would have one talk, two coffee breaks and a progress report for about a third or a half of the working groups (plus voluntary interventions in cases of specific news to report). The first day will have two talks, plus the open-problem session and formation of the groups. One board game evening.

Jean-Sébastien Sereni, Raphael Steiner, Sebastian Wiederrecht

4-8 April 2022

Registrations are now closed.

Registration form

Deadline: March, 27th.

Participants can register fully (talks + working groups) or only to attend the talks. The number of full participants is limited, and thus we might need to limit registrations, (priority given to network members).

(last update: March, 28th)

• Jean-Sébastien Sereni (organiser)
• Raphael Steiner (organiser)
• Sebastian Wiederrecht* (organiser)
• Pierre Aboulker
• Guillaume Aubian
• Maria Axenovich*
• Paul Bastide
• Nathan Bowler
• Marcin Briański
• Benjamin Merlin Bumpus
• Stijn Cambie
• Wouter Cames van Batenburg
• Linda Cook
• Victor Falgas-Ravry
• Marcelo Garlet Milani
• Ebrahim Ghorbani
• Archontia C. Giannopoulou*
• António Girão
• Maximilian Gorsky
• Florian Gut
• Santiago Guzmán-Pro
• Meike Hatzel
• Karl Heuer
• Hugo Jacob
• Ken-ichi Kawarabayashi*
• Charlotte Knierim
• Stephan Kreutzer*
• Shoham Letzter*
• Anders Martinsson
• Tomáš Masařík
• Rose McCarty
• Wojtek Nadara
• Marcin Pilipczuk
• Evangelos Protopapas
• Florian Reich
• Amadeus Reinald
• Amedeo Sgueglia
• Uéverton Souza
• Giannos Stamoulis
• Dimitrios Thilikos
• Lea Weber

* indicates speakers

Submit open problems related to the themes of the workshop by email to the organisers. One main aim of the workshop is, in small groups, to work on and solve these!

Template: download

Deadline: March, 24th.

1. Monday, Apr. 4th

• 09:30 — 10:00: Welcome & 1-minute “Hello World” from everybody.
• 10:00 — 11:00: Introduction Talk by Stephan Kreutzer.
• 11:00 — 11:15: Coffee break
• 11:15 — 12:15: Talk by Maria Axenovich on strong minors in digraphs.
• 13:15 — 14:45: Open problem session
• 14:45 — 15:00: Tea break
• 15:00 — 15:45: Partition into groups

2. Tuesday, Apr. 5th

• 09:30 — 10:15: Talk by Archontia Giannopoulou on the Directed Flat Wall Theorem.
• 10:15 — 10:30: Coffee break
• 15:00 — 16:00: Progress report
• 16:00 — 16:15: Tea break

3. Wednesday, Apr. 6th

• 09:30 — 10:15: Talk by Sebastian Wiederrecht on the relation between butterfly minor structure theory and matching theory.
• 10:15 — 10:30: Coffee break
• 15:00 — 16:00: Progress report
• 16:00 — 16:15: Tea break
• 20:00 — ??: Social event on arena (bring dice)

4. Thursday, Apr. 7th

• 09:30 — 10:15: Talk by Shoham Letzter about complete digraph immersions in Eulerian digraphs.
• 10:15 — 10:30: Coffee break
• 15:00 — 16:00: Progress report
• 16:00 — 16:15: Tea break

5. Friday, Apr. 8th

• 09:30 — 10:15: Talk by Ken-ichi Kawarabayashi on digraphs with excluded complete butterfly minors.
• 10:15 — 10:30: Coffee break
• 14:15 — 14:30: Tea break
• 14:30 — 16:00: Wrap-up meeting

To preserve the interactive nature of the meeting, no talks are to be recorded and we encourage attendees to keep their cameras on.

• Cook, Masařík, Pilipczuk, Reinald, Souza. Proving a directed analogue of the Gyárfás-Sumner conjecture for orientations of $P_4$. https://arxiv.org/abs/2209.06171