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 20, 2015, 2:15 p.m.
Michael Blondin (ENS Cachan and Université de Montréal)
joint work with Alain Finkel, Stefan Göller, Christoph Haase and Pierre McKenzie (Reachability in Two-Dimensional Vector Addition Systems with States)
Known to be decidable since 1981, there still remains a huge gapbetween the best known lower and upper bounds for the reachabilityproblem for vector addition systems with states (VASS). In this talk,the reachability problem is …
May 13, 2015, 2:15 p.m.
Filip Mazowiecki (Uniwersytet Warszawski)
joint work with Cristian Riveros (On the expressibility of copyless cost register automata)
Cost register automata (CRA) and its subclass, copyless CRA, were recently proposed as a new computational model. We study the properties and expressiveness of the copyless CRA. Our studies lead to results that copyless CRA …
May 6, 2015, 2:15 p.m.
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There is no seminar this week
April 29, 2015, 2:15 p.m.
Adam Witkowski (Uniwersytet Warszawski)
Solving datalog containment via bounded cliquewidth
Containment of monadic datalog over data trees is known to be undecidable in general but decidablefor two fragments: downward programs and linear child-only ones.I will describe a method for deciding the containment by bounding clique-width …
April 22, 2015, 2:15 p.m.
Joost Winter (Uniwersytet Warszawski)
Coinductive stream calculus
In this talk, I will give an introduction to the coinductive stream calculus (developed by Rutten, McIlroy, and others), its connection to coalgebra, automata theory and implementations in the functional programming language Haskell. We take …
April 15, 2015, 2:15 p.m.
Das Anupam (École Normale Supérieure de Lyon)
A Complete Axiomatization of MSO on Infinite Trees
We show that an adaptation of Peano’s axioms for second-orderarithmetic to the language of MSO completely axiomatizes the theoryover infinite trees. This continues a line of work begun by Büchiand Siefkes with axiomatizations of MSO …
April 8, 2015, 2:15 p.m.
Charles Paperman (Uniwersytet Warszawski)
Regular languages of AC_0
I will present a full proof of the theorem of Barington, Compton, Straubing and Therien characterizing regular languages of AC_0 based on a recent algebraic techniques.
April 1, 2015, 2:15 p.m.
Eryk Kopczyński (Uniwersytet Warszawski)
Spectra and variables
Given a formula \phi of some logic, the spectrum of \phi, denoted spec(\phi), is the set of non-negative integers n such that \phi has a model of cardinality n. The notion of a spectrum has …
March 25, 2015, 2:15 p.m.
Mikołaj Bojańczyk (Uniwersytet Warszawski)
N, <) is undecidable (The MSO+U theory of)
We consider the logic MSO+U, which is monadic second-order logic extended with the unbounding quantifier. The unbounding quantifier is used to say that a property of finite sets holds for sets of arbitrarily large size. …
March 18, 2015, 2:15 p.m.
Amaldev Manuel (Uniwersytet Warszawski)
joint work with Thomas Colcombet (Mu-calculus on data words)
I will describe Data automata, FO^2 and some natural fragments of Data automata defined by classes of Mu-calculus formulas and wrap it up by separating two classes using the circuits we discussed last time. If …
March 11, 2015, 2:15 p.m.
Charles Paperman (Uniwersytet Warszawski)
Circuits complexity and regular languages
I will talk about classical and recent developments on the subject: "Deciding the membership of regular languages in circuits complexity classes". This question is deeply interwoven with the algebraic characterization of classes of regular languages …
March 4, 2015, 2:15 p.m.
Henryk Michalewski (Uniwersytet Warszawski)
From parity games to linear optimization and back
Linear programs (LPs) can be solved efficiently, hence thedesire to reduce the parity games (PGs) to LPs. This seminar will bedevoted to a summary of attempted reductions published over the last 20 years.A polynomial solution …
Feb. 25, 2015, 2:15 p.m.
Wojciech Czerwiński (Uniwersytet Warszawski)
joint work with Wim Martens, Matthias Niewerth and Paweł Parys (Tree Pattern Minimisation)
I will consider the problem of minimising tree pattern queries. I will show you the example, which contradicted the long standing conjecture that minimality is the same as nonredundancy. Then I will present how this …
Feb. 18, 2015, 2:15 p.m.
Amaldev Manuel (Uniwersytet Warszawski)
joint work with Thomas Colcombet (Combinatorial expressions)
Combinatorial expressions are expressions built using two kinds of functions --- those having bounded arity unbounded domain (e.g. addition of integers), and those having bounded domain and unrestricted arity (e.g. Boolean OR of k inputs, …
Feb. 11, 2015, 2:15 p.m.
Szymon Toruńczyk (Uniwersytet Warszawski)
joint work with Joanna Ochremiak, Bartek Klin and Eryk Kopczyński (Orbit-finite Constraint Satisfaction Problems)
We study extensions of the classical Constraint Satisfaction Problem, to the orbit-finite setting. In one direction, we allow the instances to be orbit-finite, while preserving a finite template. We show that the problem remains decidable …