Organizers

prof. dr hab. Mikołaj Bojańczyk
prof. dr hab. Damian Niwiński

Information

Wednesdays, 2:15 p.m. , room: 5440

Research fields

List of talks

May 17, 2023, 2:15 p.m.
Liat Peterfreund (CNRS, LIGM, Paris-Est University)
Querying incomplete numerical data: between certain and possible answers
Queries with aggregation and arithmetic operations, as well as incomplete data, are common in real-world databases, but we lack a good understanding of how they should interact. On the one hand, systems based on SQL …
May 10, 2023, 2:15 p.m.
Nikolas Mählmann (University of Bremen)
Monadically Stable Classes of Graphs
Intuitively, a class of graphs is monadically stable if first-order logic cannot encode arbitrary long linear orders in it. While originating from model theory, monadic stability generalizes many combinatorial properties of sparse graph classes such …
April 26, 2023, 2:15 p.m.
Yoàv Montacute (University of Cambridge)
Logic and Dynamical Systems
The study of the relationship between logic and topology has a rich and extensive history. One way of exploring this relationship involves examining the formal languages of indiscrete spaces and their discrete representations. The talk …
April 19, 2023, 2:15 p.m.
Lorenzo Clemente (MIM UW)
Equality and zeroness problems of power series for combinatorial enumeration
A power series is constructible differentially finite (CDF) if it satisfies a system of polynomial differential equations [Bergeron & Reutenauer 1990, Bergeron & Sattler 1995]. CDF series generalise algebraic power series and find a natural …
April 12, 2023, 2:15 p.m.
Mikołaj Bojańczyk (MIM UW)
On the growth rate of polyregular functions
Polyregular functions are string-to-string functions that have polynomial size outputs. I will show that a polyregular function has growth rate O(n^k) if and only if it can be defined by an mso transduction of dimension …
April 5, 2023, 2:15 p.m.
Roland Guttenberg (TU Munich)
Geometry of Vector Addition Systems
We will prove the missing line conjecture for VAS. The proof proceeds in three steps, all based on the basic units of VAS: Periodic sets. 1) Prove an easy special case. 2) Explain all closure …
March 29, 2023, 2:15 p.m.
Giannos Stamoulis (LIRMM, Université de Montpellier, CNRS)
Model Checking Disjoint-Paths Logic on Topological-Minor-Free Graph Classes
Disjoint-paths logic, denoted FO+DP, extends first-order logic (FO) with atomic predicates dp_k[(x_1, y_1),…,(x_k, y_k)], expressing the existence of internally vertex-disjoint paths between x_i and y_i, for 1 ≤ i ≤ k. In this talk, we …
March 22, 2023, 2:15 p.m.
Wojciech Przybyszewski (MIM UW)
Reproving combinatorial properties of nowhere-dense graphs using model theory
A pinnacle of sparsity theory, initiated by Ossona de Mendez and Nešetřil, is the result of Grohe, Kreutzer, and Siebertz which identifies subgraf-closed classes of graphs with FPT model checking as exactly nowhere dense classes. …
March 15, 2023, 2:15 p.m.
Arka Ghosh (MIM UW)
Orbit-finite systems of inequalities
A system of inequalities is orbit-finite if it is finite up to certain permutations of variables. In this talk, I will describe this concept using interesting examples, and present our recent results on the solvability …
March 8, 2023, 2:15 p.m.
Michał Skrzypczak (MIM UW)
for context-free grammars (Binary counting is hard)
Michaël Cadilhac recently (on Autoboz) asked the following problem: Take n > 0 and consider the alphabet A_n = { 2^i | i ≤ n }. Let L_n be the set of words over A_n …
March 1, 2023, 2:15 p.m.
Florent Koechlin (LORIA)
Two criteria to prove the inherent ambiguity of bounded context-free languages
A context-free language is inherently ambiguous if any grammar recognizing it is ambiguous, i.e. there is a word that is generated in two different ways. Deciding the inherent ambiguity of a context-free language is a …
Jan. 25, 2023, 2:15 p.m.
Hugo Gimbert (CNRS, LaBRI, Université de Bordeaux)
Martin’s proof of Borel determinacy
Donald Martin established Borel determinacy in 1975: in every Gale-Stewart game with a Borel winning condition, either player I or player II has a winning strategy. We present Martin’s proof under a different perspective (bottom-up …
Jan. 18, 2023, 2:15 p.m.
Mikołaj Bojańczyk (MIM UW)
TBA
Jan. 11, 2023, 2:15 p.m.
Pierre Ohlmann (MIM UW)
Memory in games and universal graphs
I will present recent characterisations of positionality and finite memory in infinite duration games by means of universal graphs. The goal is to derive properties of games with a given objective W by understanding the …
Dec. 21, 2022, 2:15 p.m.
Marcin Przybyłko (University of Leipzig)
Enumerating Answers to Ontology Mediated Queries
A known dichotomy states that for conjunctive queries (CQs) with no self-joins the set of answers can be enumerated with linear preprocessing* and constant delay* if and only** if the query is both acyclic and …