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Wydział Matematyki, Informatyki i Mechaniki Uniwersytetu Warszawskiego

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Seminarium „Teoria automatów”

Cotygodniowe seminarium badawcze

Lista referatów

  • 2021-03-03, godz. 14:15, online

    Szymon Toruńczyk (MIM UW)

    Ordered graphs of bounded twin-width

    We consider hereditary classes of graphs equipped with a total order. We provide multiple equivalent characterisations of those classes which have bounded twin-width. In particular, we prove that those are exactly the classes which avoid certain large grid-like structures as induced substructures...

  • 2021-02-24, godz. 14:15, online

    Filip Mazowiecki (Max Planck Institute for Software Systems)

    Continuous One-Counter Automata

    We study the reachability problem for continuous one-counter automata, COCA for short. In such automata, transitions are guarded by upper and lower bound tests against the counter value. Additionally, the counter updates associated with taking transitions can be (non-deterministically) scaled down b...

  • 2021-01-20, godz. 14:15, online

    Mikołaj Bojańczyk and Bartek Klin (MIM UW)

    Vector spaces of orbit-finite dimension, with applications to weighted and unambiguous register automata

    We develop the theory of vector spaces spanned by orbit-finite sets, with the main technical result being finite upper bounds on the lengths of increasing chains of equivariant subspaces. We then apply this theory to weighted register automata, which are a common generalization of weighted automata ...

  • 2020-12-16, godz. 14:15, online

    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 to appear positively is for instance very natural when considering logi...

  • 2020-12-09, godz. 14:15, online

    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 show that a quasi-polynomial number of queries is sufficient, namely n^{lg(...

  • 2020-12-02, godz. 14:15, online

    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 sets with atoms. This is joint work with Sławek Lasota and Szymon Toru...

  • 2020-11-25, godz. 14:15, online

    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 and unambiguous, improving on the currently best-known 2-EXPSPACE upp...

  • 2020-11-18, godz. 14:15, online

    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 over strings and unordered trees and in general can be...

  • 2020-11-04, godz. 14:15, Online

    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). The basic idea is to conside...

  • 2020-10-21, godz. 14:15, online

    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 or rank-width. We give a model-theoretic characterizat...