Organizers

prof. dr hab. Mikołaj Bojańczyk
prof. dr hab. Damian Niwiński

Information

Wednesdays, 2:15 p.m. , room: 5440

Research fields

List of talks

Dec. 16, 2020, 2:15 p.m.
Denis Kuperberg (ENS Lyon)
Positive first-order logic on words.
I will present FO+, a restriction of first-order logic where letters are required to appear positively, and the alphabet is partially ordered (for instance by inclusion order if letters are sets of atoms). Restricting predicates …
Dec. 9, 2020, 2:15 p.m.
Paweł Parys (MIM UW)
A Quasi-Polynomial Black-Box Algorithm for Fixed Point Evaluation
We consider nested fixed-point expressions like µz.νy.µx.f(x,y,z) evaluated over a finite lattice, and ask how many queries to a function f are needed to find the value. Following a recent development for parity games, we …
Dec. 2, 2020, 2:15 p.m.
Bartek Klin (MIM UW)
Nondeterministic and co-nondeterministic implies deterministic, for data languages.
I will explain why, if a data language and its complement are both recognized by non-deterministic register automata (without guessing), then they are both recognized by deterministic ones. The proof relies on the technology of …
Nov. 25, 2020, 2:15 p.m.
Corentin Barloy (University of Lille)
Bidimensional linear recursive sequences and universality of unambiguous register automata
We study the universality and inclusion problems for register automata over equality data (A, =). We show that the universality and inclusion problems can be solved with 2-EXPTIME complexity when both automata are without guessing …
Nov. 18, 2020, 2:15 p.m.
Janusz Schmude (MIM UW)
Polynomial grammars with substitution
Polynomial grammars are grammars whose nonterminals generate tuples of integers (or elements of some ring in general) and productions use polynomial functions. They proved to be useful for proving decidability of equivalence of MSO transductions …
Nov. 4, 2020, 2:15 p.m.
Mikołaj Bojańczyk (MIM UW)
Regular expressions for data words
I will discuss a proposal (one of many others) for regular expressions that use infinite alphabets. The regular expressions describe exactly the languages that can be recognised by nondeterministic orbit-finite automata (equivalently, nondeterministic register automata). …
Oct. 21, 2020, 2:15 p.m.
Szymon Toruńczyk (Uniwersytet Warszawski (MIMUW))
A model-theoretic characterization of bounded twin-width
Twin-width is a graph parameter introduced recently in a series of papers by Bonnet, Geniet, Kim, Thomassé, and Watrigant. Among others, classes of bounded twin-width include all proper minor-closed classes, all classes of bounded tree-width …
Oct. 14, 2020, 2 p.m.
Colin Geniet (ENS Paris-Saclay)
Twin-Width of Graphs
Twin-width is a graph complexity measure based on a notion of width of permutations by Guillemot and Marx [SODA '14]. Twin-width is defined through sequences of d-contractions, which witness that the twin-width is at most …
June 24, 2020, 2:15 p.m.
Pierre Pradic (ENS Lyon)
joint work with Lê Thành Dũng (Implicit automata in λ-calculi)
This work is part of an exploration of the expressiveness of the simply-typed λ-calculus (STLC) and related substructural variants (linear, affine, planar) using Church encodings of datatypes. More specifically, we are interested in the connection …
June 17, 2020, 2:15 p.m.
Jakub Gajarsky (Uniwersytet Warszawski)
Differential games for FO logic
I will introduce differential games for FO logic of graphs, a new variant of Ehrenfeucht-Fraisse games. These games are an attempt to extend currently used locality-based techniques for FO logic in a way which works …
June 10, 2020, 2:15 p.m.
Nathanael Fijalkow (CNRS, LaBRI)
Learning Probabilistic Context-Free Grammar
In this talk I will report on a joint work with Alexander Clark about learning (a subclass of) probabilistic context-free grammars published in the Transactions of the Association for Computational Linguistics. The objective of the …
June 3, 2020, 2:15 p.m.
Julian Salamanca (Uniwersytet Warszawski)
Lattices do not distribute over powerset
I will show that there is no distributive law of the free lattice monad over the powerset monad. The proof presented also works for other classes of lattices such as (bounded) distributive/modular lattices and also …
May 27, 2020, 2:15 p.m.
Joost Winter
From automata theory to coinduction with Haskell
In this talk I will approach a topic from classical automata theory, power series in a single input variable, from the point of view of coinductive specifications in the functional language Haskell, which are easy …
May 20, 2020, 2:15 p.m.
Vincent Michielini (Uniwersytet Warszawski)
joint work with Michał Skrzypczak (Regular choices and uniformisations for countable domains)
Considering the following question: given (in a sense which will be clarified in the talk) a countable totally ordered set D, on which condition(s) does there exist a choice function over D (i.e. a function …
May 13, 2020, 2:15 p.m.
Denis Kuperberg (CNRS, LIP, ENS Lyon)
joint work with Laureline Pinault and Damien Pous (Computational content of circular proof systems)
Cyclic proofs are a class of formal proof systems that allow some kind of circular reasoning. Unlike classical proofs, represented by finite trees with axioms as leaves, cyclic proofs are represented by trees containing infinite …