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 25, 2007, 2:15 p.m.
Mikołaj Bojańczyk (Uniwersytet Warszawski)
Forest expressions
I will talk about a type of regular expression for unranked trees. The main focus is on connections with logic: the expressions correspond to chain logic, the star-free expressions correspond to first-order logic, and finally, …
April 18, 2007, 2:15 p.m.
Konrad Zdanowski (Uniwersytet Warszawski)
Undecidability methods for the word problem in finite semigroups
April 3, 2007, 2:15 p.m.
Damian Niwiński (Uniwersytet Warszawski)
Two remarks on the role of ranks in parity games
These observations are of very different nature, but they can be read as evidences for the lower bound, and the upper bound, respectively. At first we show that the number of ranks gives rise to …
March 21, 2007, 2:15 p.m.
Filip Murlak (Uniwersytet Warszawski)
Temporal Logics and Model Checking for Fairly Correct Systems
I will present recent results on model checking for fairly correct systems (D. Varacca, H. Voelzer, LICS'06). A fair variant of a specfication is obtained by replacing "for all paths" by "for a large set …
March 14, 2007, 2:15 p.m.
Pawel Parys (Uniwersytet Warszawski)
On Systems of Equations Satisfied in All Commutative Finite Semigroups
I show the algorithmic procedure for solving the problem: check if a system of equations has a solution in every commutative finite semigroup.
Feb. 28, 2007, 2:15 p.m.
Mikołaj Bojańczyk (Uniwersytet Warszawski)
A paradox for CTL
The property "every path belongs to (ab)*a(ab)*" can be expressed in CTL; but necessarily using existential modalities. This shows that ACTL;does not capture the common fragment of CTL and LTL.
Jan. 3, 2007, 2:15 p.m.
Maria Fraczak (Uniwersytet Warszawski)
Defining rational functions by deterministic pushdown transducers
Rational functions are partial functions from words to words. They are implemented by finite state automata extended to produce output; only some of them can be realized by deterministic pushdown transducers (deterministic pushdown automata producing …
Dec. 20, 2006, 2:15 p.m.
Sławomir Lasota (Uniwersytet Warszawski)
Bisimulation equivalence and commutative context-free grammars
The topic will be the class of processes (transition systems) generated from the commutative context-free grammars. I will present a method enabling to prove decidability (and to compute the complexity) of different variants of bisimulation …
Nov. 29, 2006, 2:15 p.m.
Mikołaj Bojańczyk (Uniwersytet Warszawski)
Two-way temporal logic over unranked trees
I will talk about languages of unranked trees that can be defined in a temporal logic with two operators: exists some ancestor, and exists some descendant. The point is to have an algorithm, which decides …
Nov. 23, 2006, 2:15 p.m.
Marcin Jurdziński (Uniwersytet Warszawski)
Subexponential algorithms for solving parity games
Solving parity games is polynomial time equivalent to the modal mu-calculus model checking problem and its exact computational complexity is an intriguing open problem: it is known to be in UP (unambiguous NP) and co-UP, …
Nov. 15, 2006, 2:15 p.m.
Filip Murlak (Uniwersytet Warszawski)
Weak automata and Wadge hierarchy
I will show a new lower bound for the height of the Wadge hierarchy of weak tree languages, i. e., the languages of infinite trees recognizable with weak automata. To this end I will prove …
Oct. 25, 2006, 2:15 p.m.
Jacek Jurewicz (Uniwersytet Warszawski)
Panic automata
Panic automata are an extension of second-order pushdown automata (that operate on a second-order pushdown store, ie. a stack of stacks) by the destructive "panic" operation introduced by P. Urzyczyn in order to fully relate …
Oct. 11, 2006, 2:15 p.m.
Eryk Kopczynski (Uniwersytet Warszawski)
Half-positionally determined winning conditions
Basic definitions: games, half-positional determinacy. - Half-positional winning conditions and omega-regular languages. How to check whether the given omega-regular winning condition is finitely half-positional? - Positional/suspendable conditions (PS). Definitions and examples. Half-positional determinacy of a …
Oct. 4, 2006, 2:15 p.m.
Henrik Bjorklund (Dortmund)
Toward Regular Data Languages
June 7, 2006, 2:15 p.m.
Sibylle Froeschle
The computational dichotomy of true-concurrency
In concurrency theory there is a divide between the interleaving approach, in which concurrency is reduced to nondeterministic sequentialization, and the truly-concurrent approach, which represents concurrency in a more faithful way. In this talk I …