Organizers

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

Information

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

Research fields

List of talks

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 …
Dec. 14, 2022, 2:15 p.m.
Antonio Casares Santos (LaBRI, Université de Bordeaux)
A correspondence between memory and automata for Muller languages
In this talk, we will be interested in infinite-duration games using Muller winning conditions, that is, the objective of such games is given by a boolean combination of colors that have to appear infinitely often. …
Dec. 7, 2022, 2:15 p.m.
Lorenzo Clemente (MIM UW)
Decidability of equivalence of deterministic one-way multitape finite automata
I will present an old decidability result by Harju and Karhumäki, as in the title. The original proof involves some very nice algebraic constructions, which constitute the motivation for this presentation. We start from the …
Nov. 30, 2022, 2:15 p.m.
David Purser (MIM UW)
The big-O problem for max-plus automata
Given two weighted automata A and B over the (N, max, plus) semi-ring we consider the problem of deciding whether there exists a constant c such that A(w) ≤ c B(w) + c for every …
Nov. 23, 2022, 2:15 p.m.
Jakob Piribauer (TU Dresden)
Tradeoff between expectation and variance in Markov decision processes
The stochastic shortest path problem asks to resolve the non-deterministic choices in a Markov decision process (MDP) such that the expected accumulated weight before reaching a target state is maximized. This problem is well-studied and …
Nov. 16, 2022, 2:15 p.m.
Mikołaj Bojańczyk (MIM UW)
Folding interpretations
In this talk, I will discuss a characterisation of the polyregular functions which uses folding. The idea is to use the combinator approach, i.e. start with certain atomic functions (such as list concatenation) and apply …
Nov. 9, 2022, 2:15 p.m.
Paweł Parys (MIM UW)
Weak Bisimulation Finiteness of Pushdown Systems With Deterministic ε-Transitions Is 2-EXPTIME-Complete
We consider the problem of deciding whether a given pushdown system all of whose ε-transitions are deterministic is weakly bisimulation finite, that is, whether it is weakly bisimulation equivalent to a finite system. We prove …