Organizers

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

Information

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

Research fields

List of talks

April 3, 2024, 2:15 p.m.
Tomasz Gogacz (University of Warsaw)
TBA
TBA
March 27, 2024, 2:15 p.m.
Tim Seppelt (RWTH Aachen University)
Homomorphism Indistinguishability: Characterisations, Closure, Complexity
In 1967, Lovász proved that two graphs G and H are isomorphic iff they are homomorphism indistinguishable over the the family of all graphs, i.e. for all graphs F the number of homomorphisms from F …
March 20, 2024, 2:15 p.m.
Jingjie Yang (University of Oxford)
Equivariant subspaces of orbit-finite-dimensional vector spaces (Niezmiennicze podprzestrzenie przestrzeni liniowych orbitowo skończonego wymiaru)
In their LICS21 paper, Bojańczyk, Klin, and Moerman gave an equivalence algorithm for weighted orbit-finite automata: they construct a chain of configuration spaces that are closed under both linear combinations and atom permutations; crucially, termination …
March 13, 2024, 2:15 p.m.
Alexandra Rogova
Connecting graph and relational query languages
Practical query languages for graph and relational databases are based on similar concepts: In the former, base relations are extracted from graphs, and in the latter, they are given as input. In both, these base …
March 6, 2024, 2:15 p.m.
Szymon Toruńczyk (MIMUW)
Combinatorial Characterizations of Monadically Dependent Graph Classes
We provide the first two combinatorial characterizations of monadically dependent graph classes. This yields the following dichotomy. On the structure side, we characterize monadic dependence by a property called flip-breakability. This notion generalizes the notions …
Feb. 28, 2024, 2:15 p.m.
Michał Pilipczuk (MIMUW)
First-Order Model Checking on Monadically Stable Graph Classes
A graph class C is monadically stable if one cannot interpret arbitrary long linear orders in colored graphs from C using any fixed first-order interpretation. We prove that on any monadically stable class, the model-checking …
Feb. 21, 2024, 2:15 p.m.
Vincent Michielini (University of Warsaw)
Complexity of Maslov's Class K-bar
Maslov’s class K-bar is a fragment of First-Order Logic consisting of formulae in NNF whose variables occurring in the different atoms obey a certain pattern [*]. It embeds many well-known fragments, such as the two-variable …
Feb. 14, 2024, 2:15 p.m.
Daniel Smertnig (University of Ljubljana)
On the linear hull of a weighted automaton
Previous work reduces the problem of deciding whether a weighted finite automaton (WFA) over a field is equivalent to a deterministic, respectively, unambiguous, WFA to the computation of the linear hull. The linear hull is …
Feb. 7, 2024, 2:15 p.m.
Mikołaj Bojańczyk (University of Warsaw)
On function spaces for orbit-finite sets
Joint work with Tito Nguyen and Rafał Stefański. Orbit-finite sets are a generalisation of finite sets, and as such support many operations allowed for finite sets, such as pairing, quotienting, or taking subsets. However, they …
Jan. 31, 2024, 2:15 p.m.
Cristian Riveros Jaeger (Pontificia Universidad Católica de Chile (PUC Chile))
#NFA admits an FPRAS
#NFA is the following problem over non-deterministic finite automata (NFA) over words: you receive as input an NFA A and a length N (in unary), and you want to count the number of words of …
Dec. 20, 2023, 2:15 p.m.
Julie Parreaux (University of Warsaw)
Playing stochastically in Weighted Timed Games to Emulate Memory
Weighted timed games are two-player zero-sum games played in a timed automaton equipped with integer weights. We consider optimal reachability objectives, in which one of the players, that we call Min, wants to reach a …
Dec. 13, 2023, 2:15 p.m.
Lorenzo Clemente (University of Warsaw)
Zeroness of weighted basic parallel processes and other finitely generated classes of series
We consider a weighted model of computation generalising weighted finite automata over fields, namely weighted basic parallel processes (WBPP). The underlying unweighted BPP model, popular in process algebra, was introduced by Christensen in his PhD …
Dec. 6, 2023, 2:15 p.m.
Antonio Casares (University of Warsaw)
A characterization of half-positionality for omega-regular languages
In the context of infinite duration games over graphs, a central question is: For which objectives can the existential player always play optimally using positional (memoryless) strategies? In this talk, we characterize omega-regular objectives with …
Nov. 29, 2023, 2:15 p.m.
Ruiwen Dong (Saarland University)
Decidability problems in infinite semigroups
This talk is about several algorithmic problems for matrix semigroups. A classic problem in this area is the well-known Semigroup Membership problem: given as input a finite set of square matrices S = {A1, A2, …
Nov. 22, 2023, 2:15 p.m.
Rafał Stefański (University of Warsaw)
Recognisable transducers over monads and comonads
In 2015, Bojańczyk introduced a class of recognizable languages over monads, which is a common generalization of regular languages for many different types of objects, including words, infinite words, and trees. In this talk, I …