7 Search Results for "Velebil, Jiří"

Document
DOI: 10.4230/LIPIcs.CSL.2026.24
Well-Founded Coalgebras Meet Kőnig’s Lemma

Authors: Henning Urbat and Thorsten Wißmann

Published in: LIPIcs, Volume 363, 34th EACSL Annual Conference on Computer Science Logic (CSL 2026)

Abstract
Kőnig’s lemma is a fundamental result about trees with countless applications in mathematics and computer science. In contrapositive form, it states that if a tree is finitely branching and well-founded (i.e. has no infinite paths), then it is finite. We present a coalgebraic version of Kőnig’s lemma featuring two dimensions of generalization: from finitely branching trees to coalgebras for a finitary endofunctor H, and from the base category of sets to a locally finitely presentable category ℂ, such as the category of posets, nominal sets, or convex sets. Our coalgebraic Kőnig’s lemma states that, under mild assumptions on ℂ and H, every well-founded coalgebra for H is the directed join of its well-founded subcoalgebras with finitely generated state space - in particular, the category of well-founded coalgebras is locally presentable. As applications, we derive versions of Kőnig’s lemma for graphs in a topos as well as for nominal and convex transition systems. Additionally, we show that the key construction underlying the proof gives rise to two simple constructions of the initial algebra (equivalently, the final recursive coalgebra) for the functor H: The initial algebra is both the colimit of all well-founded and of all recursive coalgebras with finitely presentable state space. Remarkably, this result holds even in settings where well-founded coalgebras form a proper subclass of recursive ones. The first construction of the initial algebra is entirely new, while for the second one our approach yields a short and transparent new correctness proof.
Cite as

Henning Urbat and Thorsten Wißmann. Well-Founded Coalgebras Meet Kőnig’s Lemma. In 34th EACSL Annual Conference on Computer Science Logic (CSL 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 363, pp. 24:1-24:19, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{urbat_et_al:LIPIcs.CSL.2026.24,
  author =	{Urbat, Henning and Wi{\ss}mann, Thorsten},
  title =	{{Well-Founded Coalgebras Meet K\H{o}nig’s Lemma}},
  booktitle =	{34th EACSL Annual Conference on Computer Science Logic (CSL 2026)},
  pages =	{24:1--24:19},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-411-6},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{363},
  editor =	{Guerrini, Stefano and K\"{o}nig, Barbara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2026.24},
  URN =		{urn:nbn:de:0030-drops-254485},
  doi =		{10.4230/LIPIcs.CSL.2026.24},
  annote =	{Keywords: K\H{o}nig’s Lemma, Well-Foundedness, Coalgebra}
}
Document
Invited Paper
DOI: 10.4230/LIPIcs.CSL.2026.3
Rational Lawvere Logic (Invited Paper)

Authors: Giorgio Bacci, Radu Mardare, Prakash Panangaden, and Gordon Plotkin

Published in: LIPIcs, Volume 363, 34th EACSL Annual Conference on Computer Science Logic (CSL 2026)

Abstract
We study Rational Lawvere logic (RL). This logic is defined over the extended positive reals with an algebraic structure combining the Lawvere quantale (with the reversed order on the extended reals and a sum as tensor) and a multiplicative quantale (with the usual order on the extended reals and a multiplication as tensor); together they provide a semiring structure. The logic is designed for complex quantitative reasoning, including sequents expressing inequalities between rational functions over the extended positive reals. We give a deduction system and demonstrate its expressiveness by deriving a classical result from probability theory relating the Kantorovich and total variation distances. Our deductive system is complete for finitely axiomatizable theories. The proof of completeness relies on the Krivine-Stengle Positivstellensatz. We additionally provide complexity results for both RL and its affine fragment AL. We consider two decision problems: the satisfiability of a set of sequents and whether a sequent follows from a finite set of sequent. We show that both problems lie in PSPACE for RL, and we give sharper complexity bounds for AL: the first problem is NP-complete, while the second is co-NP-complete.
Cite as

Giorgio Bacci, Radu Mardare, Prakash Panangaden, and Gordon Plotkin. Rational Lawvere Logic (Invited Paper). In 34th EACSL Annual Conference on Computer Science Logic (CSL 2026). Leibniz International Proceedings in Informatics (LIPIcs), Volume 363, pp. 3:1-3:21, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2026)

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@InProceedings{bacci_et_al:LIPIcs.CSL.2026.3,
  author =	{Bacci, Giorgio and Mardare, Radu and Panangaden, Prakash and Plotkin, Gordon},
  title =	{{Rational Lawvere Logic}},
  booktitle =	{34th EACSL Annual Conference on Computer Science Logic (CSL 2026)},
  pages =	{3:1--3:21},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-411-6},
  ISSN =	{1868-8969},
  year =	{2026},
  volume =	{363},
  editor =	{Guerrini, Stefano and K\"{o}nig, Barbara},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CSL.2026.3},
  URN =		{urn:nbn:de:0030-drops-254277},
  doi =		{10.4230/LIPIcs.CSL.2026.3},
  annote =	{Keywords: Quantitative reasoning, complete deductive system, Lawvere’s quantale}
}
Document
Invited Talk
DOI: 10.4230/LIPIcs.CALCO.2025.2
Logic Enriched over a Quantale (Invited Talk)

Authors: Alexander Kurz

Published in: LIPIcs, Volume 342, 11th Conference on Algebra and Coalgebra in Computer Science (CALCO 2025)

Abstract
Many-valued logics have a long history in mathematical logic as well as in applications to the semantics of programming languages and to engineering more generally. Typically these logics are rich with features motivated by the particular applications they stem from. In his 1973 article "Metric Spaces, Generalized Logic, and Closed Categories", Lawvere argued that any quantale Ω gives rise to a generalized Ω-valued logic that has as its models the categories enriched over the quantale. This suggests developing a uniform framework for many-valued logics parameterized in a quantale. In this talk we will review some previous and ongoing work in that direction. In particular, we will address (not necessarily answer) the following questions. - If we take as our starting point, generalizing from 2-valued lattice logic, a logical language that comprises not only meets and joins (limits and colimits) but also tensor and power (weighted limits and colimits), what laws do these operations satisfy? - This question can be investigated for different types of semantics, generalizing the set-theoretic and the polarity-based semantics known from the 2-valued setting. - Which additional properties obtain if the quantale is integral or commutative or finite or distributive, etc? - On the other hand, quantale logics can also be investigated from a purely proof theoretic point of view, leading us to consider sequent calculi with turnstiles ⊢_ω labelled by elements ω ∈ Ω. - As Galatos and Jipsen showed, there are 1662 "Residuated Lattices of Size up to 6". Each of them generates a different and potentially interesting logic. - The adjunction Ω^-⊣ Ω^-:Ω-cat^op → Ω-cat exists for any quantale Ω. What is the logic enshrined in the monad of that adjunction? How far can one extend this to a theory of Stone duality for quantale logics parametric in the quantale? - The Dedekind-MacNeille completion generalizes to quantale categories. Similarly, the theory of canonical extensions originating with Jonsson and Tarski (and important for completeness proofs of modal logics) can be extended to quantale logics. - Since the discrete functor Set → Ω-cat is dense in the sense of Kelly, set-functors (equipped with an Ω-cat structure or not) can be extended to quantale categories via enriched left Kan extensions. This gives rise to a uniform variety of type constructors (endofunctors) on quantale categories parameterised by the quantale. - Each endofunctor on Ω-cat gives rise to a category of coalgebras with their own notion of behavioural equivalence. How many of the existing notions of many-valued (probabilistic, metric, fuzzy, etc) bisimulation can be accounted for in this uniform framework? - Morphism between quantales gives rise to change-of-base principles between categories of (co)algebras. Which transfer principles can be obtained from a systematic investigation of change of base for quantale categories? - Exploiting the duality of coalgebras (as models of computation) and algebras (as modal logics), which general logical theory of computation arises from putting the items in this list together?
Cite as

Alexander Kurz. Logic Enriched over a Quantale (Invited Talk). In 11th Conference on Algebra and Coalgebra in Computer Science (CALCO 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 342, p. 2:1, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{kurz:LIPIcs.CALCO.2025.2,
  author =	{Kurz, Alexander},
  title =	{{Logic Enriched over a Quantale}},
  booktitle =	{11th Conference on Algebra and Coalgebra in Computer Science (CALCO 2025)},
  pages =	{2:1--2:1},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-383-6},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{342},
  editor =	{C\^{i}rstea, Corina and Knapp, Alexander},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CALCO.2025.2},
  URN =		{urn:nbn:de:0030-drops-235609},
  doi =		{10.4230/LIPIcs.CALCO.2025.2},
  annote =	{Keywords: Modal Logic, Coalgebra, Enriched Category Theory}
}
Document
Track B: Automata, Logic, Semantics, and Theory of Programming
DOI: 10.4230/LIPIcs.ICALP.2025.152
Tree Algebras and Bisimulation-Invariant MSO on Finite Graphs

Authors: Thomas Colcombet, Amina Doumane, and Denis Kuperberg

Published in: LIPIcs, Volume 334, 52nd International Colloquium on Automata, Languages, and Programming (ICALP 2025)

Abstract
We establish that the bisimulation invariant fragment of MSO over finite transition systems is expressively equivalent over finite transition systems to modal μ-calculus, a question that had remained open for several decades. The proof goes by translating the question to an algebraic framework, and showing that the languages of regular trees that are recognised by finitary tree algebras whose sorts zero and one are finite are the regular ones. This corresponds for trees to a weak form of the key translation of Wilke algebras to omega-semigroup over infinite words, and was also a missing piece in the algebraic theory of regular languages of infinite trees for twenty years.
Cite as

Thomas Colcombet, Amina Doumane, and Denis Kuperberg. Tree Algebras and Bisimulation-Invariant MSO on Finite Graphs. In 52nd International Colloquium on Automata, Languages, and Programming (ICALP 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 334, pp. 152:1-152:16, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{colcombet_et_al:LIPIcs.ICALP.2025.152,
  author =	{Colcombet, Thomas and Doumane, Amina and Kuperberg, Denis},
  title =	{{Tree Algebras and Bisimulation-Invariant MSO on Finite Graphs}},
  booktitle =	{52nd International Colloquium on Automata, Languages, and Programming (ICALP 2025)},
  pages =	{152:1--152:16},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-372-0},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{334},
  editor =	{Censor-Hillel, Keren and Grandoni, Fabrizio and Ouaknine, Jo\"{e}l and Puppis, Gabriele},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ICALP.2025.152},
  URN =		{urn:nbn:de:0030-drops-235294},
  doi =		{10.4230/LIPIcs.ICALP.2025.152},
  annote =	{Keywords: MSO, mu-calculus, finite graphs, bisimulation, tree algebra}
}
Document
DOI: 10.4230/LIPIcs.STACS.2025.10
Monotone Weak Distributive Laws over the Lifted Powerset Monad in Categories of Algebras

Authors: Quentin Aristote

Published in: LIPIcs, Volume 327, 42nd International Symposium on Theoretical Aspects of Computer Science (STACS 2025)

Abstract
In both the category of sets and the category of compact Hausdorff spaces, there is a monotone weak distributive law that combines two layers of non-determinism. Noticing the similarity between these two laws, we study whether the latter can be obtained automatically as a weak lifting of the former. This holds partially, but does not generalize to other categories of algebras. We then characterize when exactly monotone weak distributive laws over powerset monads in categories of algebras exist, on the one hand exhibiting a law combining probabilities and non-determinism in compact Hausdorff spaces and showing on the other hand that such laws do not exist in a lot of other cases.
Cite as

Quentin Aristote. Monotone Weak Distributive Laws over the Lifted Powerset Monad in Categories of Algebras. In 42nd International Symposium on Theoretical Aspects of Computer Science (STACS 2025). Leibniz International Proceedings in Informatics (LIPIcs), Volume 327, pp. 10:1-10:20, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2025)

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@InProceedings{aristote:LIPIcs.STACS.2025.10,
  author =	{Aristote, Quentin},
  title =	{{Monotone Weak Distributive Laws over the Lifted Powerset Monad in Categories of Algebras}},
  booktitle =	{42nd International Symposium on Theoretical Aspects of Computer Science (STACS 2025)},
  pages =	{10:1--10:20},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-365-2},
  ISSN =	{1868-8969},
  year =	{2025},
  volume =	{327},
  editor =	{Beyersdorff, Olaf and Pilipczuk, Micha{\l} and Pimentel, Elaine and Thắng, Nguy\~{ê}n Kim},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.STACS.2025.10},
  URN =		{urn:nbn:de:0030-drops-228356},
  doi =		{10.4230/LIPIcs.STACS.2025.10},
  annote =	{Keywords: weak distributive law, weak extension, weak lifting, iterated distributive law, Yang-Baxter equation, powerset monad, Vietoris monad, Radon monad, Eilenberg-Moore category, regular category, relational extension}
}
Document
DOI: 10.4230/LIPIcs.CALCO.2023.10
Strongly Finitary Monads for Varieties of Quantitative Algebras

Authors: Jiří Adámek, Matěj Dostál, and Jiří Velebil

Published in: LIPIcs, Volume 270, 10th Conference on Algebra and Coalgebra in Computer Science (CALCO 2023)

Abstract
Quantitative algebras are algebras enriched in the category Met of metric spaces or UMet of ultrametric spaces so that all operations are nonexpanding. Mardare, Plotkin and Panangaden introduced varieties (aka 1-basic varieties) as classes of quantitative algebras presented by quantitative equations. We prove that, when restricted to ultrametrics, varieties bijectively correspond to strongly finitary monads T on UMet. This means that T is the left Kan extension of its restriction to finite discrete spaces. An analogous result holds in the category CUMet of complete ultrametric spaces.
Cite as

Jiří Adámek, Matěj Dostál, and Jiří Velebil. Strongly Finitary Monads for Varieties of Quantitative Algebras. In 10th Conference on Algebra and Coalgebra in Computer Science (CALCO 2023). Leibniz International Proceedings in Informatics (LIPIcs), Volume 270, pp. 10:1-10:14, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2023)

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@InProceedings{adamek_et_al:LIPIcs.CALCO.2023.10,
  author =	{Ad\'{a}mek, Ji\v{r}{\'\i} and Dost\'{a}l, Mat\v{e}j and Velebil, Ji\v{r}{\'\i}},
  title =	{{Strongly Finitary Monads for Varieties of Quantitative Algebras}},
  booktitle =	{10th Conference on Algebra and Coalgebra in Computer Science (CALCO 2023)},
  pages =	{10:1--10:14},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-95977-287-7},
  ISSN =	{1868-8969},
  year =	{2023},
  volume =	{270},
  editor =	{Baldan, Paolo and de Paiva, Valeria},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CALCO.2023.10},
  URN =		{urn:nbn:de:0030-drops-188078},
  doi =		{10.4230/LIPIcs.CALCO.2023.10},
  annote =	{Keywords: quantitative algebras, ultra-quantitative algebras, strongly finitary monads, varieties}
}
Document
DOI: 10.4230/LIPIcs.CALCO.2015.17
Extensions of Functors From Set to V-cat

Authors: Adriana Balan, Alexander Kurz, and Jiri Velebil

Published in: LIPIcs, Volume 35, 6th Conference on Algebra and Coalgebra in Computer Science (CALCO 2015)

Abstract
We show that for a commutative quantale V every functor from Set to V-cat has an enriched left-Kan extension. As a consequence, coalgebras over Set are subsumed by coalgebras over V-cat. Moreover, one can build functors on V-cat by equipping Set-functors with a metric.
Cite as

Adriana Balan, Alexander Kurz, and Jiri Velebil. Extensions of Functors From Set to V-cat. In 6th Conference on Algebra and Coalgebra in Computer Science (CALCO 2015). Leibniz International Proceedings in Informatics (LIPIcs), Volume 35, pp. 17-34, Schloss Dagstuhl – Leibniz-Zentrum für Informatik (2015)

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@InProceedings{balan_et_al:LIPIcs.CALCO.2015.17,
  author =	{Balan, Adriana and Kurz, Alexander and Velebil, Jiri},
  title =	{{Extensions of Functors From Set to V-cat}},
  booktitle =	{6th Conference on Algebra and Coalgebra in Computer Science (CALCO 2015)},
  pages =	{17--34},
  series =	{Leibniz International Proceedings in Informatics (LIPIcs)},
  ISBN =	{978-3-939897-84-2},
  ISSN =	{1868-8969},
  year =	{2015},
  volume =	{35},
  editor =	{Moss, Lawrence S. and Sobocinski, Pawel},
  publisher =	{Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
  address =	{Dagstuhl, Germany},
  URL =		{https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.CALCO.2015.17},
  URN =		{urn:nbn:de:0030-drops-55244},
  doi =		{10.4230/LIPIcs.CALCO.2015.17},
  annote =	{Keywords: enriched category, quantale, final coalgebra}
}
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