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

May 10, 2006, 2:15 p.m.
Slawomir Lasota (joint work with Wojciech Rytter) (Uniwersytet Warszawski)
On language and bisimulation equivalence of contextfree processes
In contrast to language equivalence, being undecidable for (normed) contextfree grammars, the bisimulation equivalence is decidable; and it is even polynomial for normed grammars.The fastest known algorithm for checking bisimulation equivalence worked in $O(n^{13})$ time. …

April 26, 2006, 2:15 p.m.
Linh Anh Nguyen (joint work with Rajeev Gore) (Uniwersytet Warszawski)
Tableaux for Regular Grammar Logics of Agents Using AutomatonModal Formulae
A grammar logic is a multimodal logic extending Kn with inclusion axioms of the form [t1]...[th]j (r) [s1]...[sk]j where t1, ..., th, s1, ..., sk are modal indices. Such an axiom can be seen as …

March 29, 2006, 2:15 p.m.
Mikolaj Bojanczyk (Uniwersytet Warszawski)
Reachability in vectoraddition systems
An (ndimensional) vector addition system is a finite set V of ndimensional integer vectors. The reachability problem is as follows: given V and two ndimensional vectors of *naturals * v and w, determine if one …

March 22, 2006, 2:15 p.m.
Piotr Hoffman (Uniwersytet Warszawski)
Word problems in sums of monoids
In the talk I will investigate the decidability of word problems for amalgams (sums) of monoids. Word problems for amalgams of monoids are equivalent to sums of congruence relations on words. They are also equivalent …

March 15, 2006, 2:15 p.m.
Hugo Gimbert
Positional Stochastic Strategies
We present ongoing work on positionality of fullinformation, twoplayer, zerosum stochastic games with finitely many states.

March 3, 2006, 2:15 p.m.
Emanuel Kieronski (Wroclaw, joint work with Martin Otto)
Logic with two variables and equivalence relations
We study firstorder logic with two variables FO2 and establish a small substructure property. Similar to the small model property for FO2 we obtain an exponential size bound on embedded substructures, relative to a fixed …

Feb. 22, 2006, 2:15 p.m.
Mikolaj Bojanczyk (Joint work with C. David, A. Muscholl, L. Segoufin and T. Schwentick. ) (Uniwersytet Warszawski)
Data words
A data word is a word that is annotated with data values. Every position in a data word has the usual label from a finite alphabet, but it also has a label from an infinite …

Jan. 18, 2006, 2:15 p.m.
Filip Murlak (Uniwersytet Warszawski)
Games for the Wadge Hierarchy of Deterministic Tree Languages
In the case of infinite words, the hierarchy of regular languages defined by continuous reductions is well understood since Wagner's 1977 paper. In particular, there exists a procedure calculating the exact level of a given …

Dec. 14, 2005, 2:15 p.m.
Eryk Kopczynski (Uniwersytet Warszawski)
Halfpositionally determined winning conditions in infinite games
We consider halfpositionally determined winning conditions in infinite games played on a graph by two antagonistic players Eve and Adam. We call a winning condition W _positionally determined_ if, for every infinite game (G,W) using …

Dec. 7, 2005, 2:15 p.m.
Thomas Colcombet (Rennes) (Uniwersytet Warszawski)
Infnite games on finite graphs
We consider games played on an arena (a graph) by two antagonistic players. In such a game, each player, when there is its turn, chooses an edge to follow, originating in the current position. The …

Dec. 7, 2005, 2 p.m.
Thomas COLCOMBET (Uniwersytet w Rennes (Francja), CNRS)
Infinite games on finite graphs
Autorskie streszczenie wykladu: We consider games played on an arena (a graph) by two antagonistic players. In such a game, each player, when there is its turn, chooses an edge to follow, originating in the …

Nov. 30, 2005, 2:15 p.m.
Slawomir Lasota (Uniwersytet Warszawski)
Oneclock timed automata
For timed automata with two clocks emptyness in decidable but universality and containment are not. We will show that all these problems are decidable for alternating timed automata, but with only one clock. The nonprimitiverecursive …

Nov. 23, 2005, 2:15 p.m.
Slawomir Lasota (Uniwersytet Warszawski)
Complexity of bisimulation equivalence
An overview of known results and open problems in checking bisimulation equivalence on infinite graphs. In particular, graphs generated by contextfree grammars and pushdown automata will be considered. Relationship to language equivalence will be pointed …

Nov. 18, 2005, 2:15 p.m.
Stephan Kreutzer (Uniwersytet Warszawski)
DAGwidth and Parity Games
Treewidth is a wellknown metric on undirected graphs that measures how treelike a graph is and gives a notion of graph decomposition that proves useful in algorithm development. Treewidth is characterised by a game known …

Nov. 2, 2005, 2:15 p.m.
Hugo Gimbert (joint work with Wieslaw Zielonka)
Positional Payoff Games
I will present some results about the existence of positional optimal strategies in twoplayers antagonistic games and of positional Nash equilibria in multiplayer games

Oct. 19, 2005, 2:15 p.m.
Damian Niwinski (joint work with T. Knapik, P. Urzyczyn, and I. Walukiewicz) (Uniwersytet Warszawski)
Model checking of panic automata
Panic automata, invented by Pawel Urzyczyn, extend the concept of 2nd order pushdown automata (with stacks of stacks), by a destructive move called panic. They are in a sense equivalent to 2nd order tree grammars. …

Oct. 5, 2005, 2:15 p.m.
Mikolaj Bojanczyk (joint with Igor Walukiewicz) (Uniwersytet Warszawski)
Unranked Tree Algebra
I will present an algebra for recognizing languages of unranked, finite trees. This algebra is a special case of a transformation semigroup. The talk will focus on analyzing algebras that correspond to languages defined in …