Weekly research seminar
Organizers
 prof. dr hab. Mikołaj Bojańczyk
 prof. dr hab. Damian Niwiński
Information
Wednesdays, 2:15 p.m. , room: 5050Research fields
List of talks

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 nondeterministic choices in a Markov decision process (MDP) such that the expected accumulated weight before reaching a target state is maximized. This problem is wellstudied 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 εTransitions Is 2EXPTIMEComplete
We consider the problem of deciding whether a given pushdown system all of whose εtransitions are deterministic is weakly bisimulation finite, that is, whether it is weakly bisimulation equivalent to a finite system. We prove …

Oct. 26, 2022, 2:15 p.m.
Michael Blondin (Université de Sherbrooke)
Separators in continuous Petri nets
In this talk, we will consider Petri nets: a wellestablished formalism for the analysis of concurrent systems. Testing whether a target Petri net configuration cannot be reached often amounts to proving the absence of bugs …

Oct. 19, 2022, 2:15 p.m.
Szymon Toruńczyk (MIM UW)
On monadically stable and monadically NIP classes of graphs
Sparsity theory, initiated by Ossona de Mendez and Nesetril, identifies those classes of sparse graphs that are tractable in various ways (e.g. from the perspective of the model checking problem for first order logic) as …

Oct. 11, 2022, 2:15 p.m.
Stefan Göller (Universität Kassel)
The AC0complexity of visibly pushdown languages.
The talk will be on the question which visibly pushdown languages (VPLs) are in the complexity class AC0. We provide a conjectural characterization that isolates a stubborn subclass of very particular oneturn visibly pushdown languages …

Oct. 5, 2022, 2:15 p.m.
Nguyễn Lê Thành Dũng (École normale supérieure de Lyon)
A transducer model for simply typed λdefinable functions
Among the natural ways to define functions ℕ^k > ℕ in the simply typed λcalculus, one of them allows hyperexponential growth (any tower of exponentials) but excludes many basic functions such as subtraction and equality, …

June 15, 2022, 2:15 p.m.
Albert Gutowski (MIM UW)
Finite entailment of UCRPQs over ALC ontologies
We solve finite ontologymediated query entailment for ontologies expressed in ALC (a description logic, closely related to (multi)modal logic) and queries expressed as UCRPQs (extending UCQs  unions of conjunctive queries  with constraints on …

June 8, 2022, 2:15 p.m.
Jędrzej Kołodziejski (MIM UW)
Multivalued Fixpoint Logic
We investigate multivalued fixpoint logic, an extension of the classical mucalculus where logical values range over a fixed complete lattice A equipped with monotone operations as connectives. We present equivalent game semantics for the logic …

June 1, 2022, 2:15 p.m.
Michał Skrzypczak (MIM UW)
Computing measures of regular languages via fixpoint expressions
During the talk I will present our ongoing work with Damian Niwiński and Paweł Parys on computing measures of regular languages. Our approach (following earlier results with Marcin Przybyłko) is to reduce the problem to …

May 25, 2022, 2:15 p.m.
Olivier Carton; Sebastian Maneth (University of Paris; University of Bremen)
Tight links between normality and automata; Two Applications of the Parikh Property
Abstract (Tight links between normality and automata): Normality has been introduced by É. Borel more than one hundred years ago. A real number is normal to an integer base if, in its infinite expansion expressed …

May 11, 2022, 2:15 p.m.
Filip Mazowiecki (MIM UW)
The complexity of soundness in workflow nets
Workflow nets are a popular variant of Petri nets that allow for algorithmic formal analysis of business processes. The central decision problems concerning workflow nets deal with soundness, where the initial and final configurations are …

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 SkolemMahlerLech 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 twinwidth and its consequences
During the talk, we will study set systems formed by neighborhoods in graphs of bounded twinwidth. In particular, we will show how, for a given graph from a class of graphs of bounded twinwidth, to …

April 6, 2022, 2:15 p.m.
Rose McCarty (MIM UW)
Vertexminors: 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 …