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 27, 2022, 2:15 p.m.
David Purser (MIM UW)
The Skolem Problem for Simple Linear Recurrence Sequences
The Skolem Problem, asks to decide whether a linear recurrence sequence has a zero term. The Skolem-Mahler-Lech theorem states that the set of zeros of a linear recurrence sequence is the union of a finite …
April 20, 2022, 2:15 p.m.
Wojciech Przybyszewski (MIM UW)
Definability of neighborhoods in graphs of bounded twin-width and its consequences
During the talk, we will study set systems formed by neighborhoods in graphs of bounded twin-width. In particular, we will show how, for a given graph from a class of graphs of bounded twin-width, to …
April 6, 2022, 2:15 p.m.
Rose McCarty (MIM UW)
Vertex-minors: dense graphs from sparse graphs
Structural graph theory has traditionally focused on graph classes that are sparse (that is, only contain graphs with few edges). Lately, however, there has been an ongoing shift towards the dense setting. In the first …
March 23, 2022, 2:15 p.m.
Marcin Jurdziński (University of Warwick)
Attractor decompositions and their applications in games and automata
An attractor decomposition is a natural inductively defined decomposition of a graph that satisfies the parity condition, and its “shape” can be described by an ordered tree. The McNaughton-Zielonka algorithm implicitly produces an attractor decomposition …
March 16, 2022, 2:15 p.m.
Michał Pilipczuk (MIM UW)
Dimension of posets of bounded cliquewidth
Dimension and boolean dimension are two structural measures for posets (partially ordered sets). Roughly speaking, they measure the minimum number of linear orders sufficient for encoding the poset. We will discuss a proof that posets …
March 9, 2022, 2:15 p.m.
Marie Fortin (University of Liverpool)
How undecidable are HyperLTL and HyperCTL*?
Temporal logics for the specification of information-flow properties are able to express relations between multiple executions of a system. Two of the most important such logics are HyperLTL and HyperCTL*, which generalise LTL and CTL* …
March 2, 2022, 2:15 p.m.
Rafał Stefański (MIM UW)
Single-use automata and transducers—current standpoint
Register automata (as defined by Kaminski and Francez) are an established tool for studying languages and transductions over infinite alphabets. They share many desired properties of finite automata, but they also miss a few key …
Jan. 26, 2022, 2:15 p.m.
Jan Otop (Instytut Informatyki, Uniwersytet Wrocławski)
Active learning automata with syntactic queries
Regular languages can be actively learned with membership and equivalence queries in polynomial time. The learning algorithm, called the L^* algorithm, constructs iteratively the right congruence relation of a given regular language L, and returns …
Jan. 19, 2022, 2:15 p.m.
Łukasz Orlikowski (MIM UW)
Improved Lower Bounds for the Reachability Problem in Fixed Dimensional VASSes
Complexity of the reachability problem in Vector Addition Systems (VASes) was a long standing problem for a few decades. Despite settling the computational complexity of the reachability problem in VASSes to be Ackermann-complete a lot …
Jan. 12, 2022, 2:15 p.m.
Pierre Ohlmann (MIM UW)
Characterising one-player positionality for infinite duration games on graphs
I will present a new result, asserting that a winning condition (or, more generally, a valuation) which admits a neutral letter is positional over arbitrary arenas if and only if for all cardinals there exists …
Dec. 22, 2021, 2:15 p.m.
Marcin Przybyłko (University of Bremen)
Answer Counting and Guarded TGDs
Answer Counting is simply the problem of counting the number of solutions to a given query. Tuple-Generating Dependencies (TGDs) are a common formalism for formulating database constraints. A TGD states that if certain facts are …
Dec. 15, 2021, 2:15 p.m.
Filip Mazowiecki (Max Planck Institute for Software Systems)
The boundedness and zero isolation problems for weighted automata over nonnegative rationals
We consider linear cost-register automata (equivalently, weighted automata) over the semiring of nonnegative rationals, which generalise probabilistic automata. The two problems boundedness and zero isolation ask whether there is a sequence of words that converge …
Dec. 8, 2021, 2:15 p.m.
Arka Ghosh (MIM UW)
Joint work with P.Hofman and S.Lasota (Orbit-finite System of Linear Equations)
An orbit-finite system of linear equations is a system of linear equations where the equations and the variables used in them are possibly infinite but are finite up to certain symmetries. I will start with …
Dec. 1, 2021, 2:15 p.m.
Ismaël Jecker (MIM UW)
Composite automata
A finite automaton A is called composite if there exist automata A1, A2, . . . , Ak smaller than A such that the language of A is equal to the intersection of the languages …
Nov. 24, 2021, 2:15 p.m.
Krzysztof Ziemiański (MIM UW)
joint work with U. Fahrenberg, C. Johansen, G. Struth (Languages of higher dimensional automata and Kleene theorem)
Higher dimensional automata (HDA) are a formalism for modeling concurrent systems introduced by Pratt and van Glabbeek. I will present several ways to define languages of HDA, which are collections of interval pomsets closed under …