101 research outputs found
Canonical extension and canonicity via DCPO presentations
The canonical extension of a lattice is in an essential way a two-sided
completion. Domain theory, on the contrary, is primarily concerned with
one-sided completeness. In this paper, we show two things. Firstly, that the
canonical extension of a lattice can be given an asymmetric description in two
stages: a free co-directed meet completion, followed by a completion by
\emph{selected} directed joins. Secondly, we show that the general techniques
for dcpo presentations of dcpo algebras used in the second stage of the
construction immediately give us the well-known canonicity result for bounded
lattices with operators.Comment: 17 pages. Definition 5 was revised slightly, without changing any of
the result
Quantifiers on languages and codensity monads
This paper contributes to the techniques of topo-algebraic recognition for
languages beyond the regular setting as they relate to logic on words. In
particular, we provide a general construction on recognisers corresponding to
adding one layer of various kinds of quantifiers and prove a corresponding
Reutenauer-type theorem. Our main tools are codensity monads and duality
theory. Our construction hinges on a measure-theoretic characterisation of the
profinite monad of the free S-semimodule monad for finite and commutative
semirings S, which generalises our earlier insight that the Vietoris monad on
Boolean spaces is the codensity monad of the finite powerset functor.Comment: 30 pages. Presentation improved and details of several proofs added.
The main results are unchange
Sheaf representations of MV-algebras and lattice-ordered abelian groups via duality
We study representations of MV-algebras -- equivalently, unital
lattice-ordered abelian groups -- through the lens of Stone-Priestley duality,
using canonical extensions as an essential tool. Specifically, the theory of
canonical extensions implies that the (Stone-Priestley) dual spaces of
MV-algebras carry the structure of topological partial commutative ordered
semigroups. We use this structure to obtain two different decompositions of
such spaces, one indexed over the prime MV-spectrum, the other over the maximal
MV-spectrum. These decompositions yield sheaf representations of MV-algebras,
using a new and purely duality-theoretic result that relates certain sheaf
representations of distributive lattices to decompositions of their dual
spaces. Importantly, the proofs of the MV-algebraic representation theorems
that we obtain in this way are distinguished from the existing work on this
topic by the following features: (1) we use only basic algebraic facts about
MV-algebras; (2) we show that the two aforementioned sheaf representations are
special cases of a common result, with potential for generalizations; and (3)
we show that these results are strongly related to the structure of the
Stone-Priestley duals of MV-algebras. In addition, using our analysis of these
decompositions, we prove that MV-algebras with isomorphic underlying lattices
have homeomorphic maximal MV-spectra. This result is an MV-algebraic
generalization of a classical theorem by Kaplansky stating that two compact
Hausdorff spaces are homeomorphic if, and only if, the lattices of continuous
[0, 1]-valued functions on the spaces are isomorphic.Comment: 36 pages, 1 tabl
Priestley duality for MV-algebras and beyond
We provide a new perspective on extended Priestley duality for a large class
of distributive lattices equipped with binary double quasioperators. Under this
approach, non-lattice binary operations are each presented as a pair of partial
binary operations on dual spaces. In this enriched environment, equational
conditions on the algebraic side of the duality may more often be rendered as
first-order conditions on dual spaces. In particular, we specialize our general
results to the variety of MV-algebras, obtaining a duality for these in which
the equations axiomatizing MV-algebras are dualized as first-order conditions
A non-commutative Priestley duality
We prove that the category of left-handed strongly distributive skew lattices
with zero and proper homomorphisms is dually equivalent to a category of
sheaves over local Priestley spaces. Our result thus provides a non-commutative
version of classical Priestley duality for distributive lattices and
generalizes the recent development of Stone duality for skew Boolean algebras.
From the point of view of skew lattices, Leech showed early on that any
strongly distributive skew lattice can be embedded in the skew lattice of
partial functions on some set with the operations being given by restriction
and so-called override. Our duality shows that there is a canonical choice for
this embedding.
Conversely, from the point of view of sheaves over Boolean spaces, our
results show that skew lattices correspond to Priestley orders on these spaces
and that skew lattice structures are naturally appropriate in any setting
involving sheaves over Priestley spaces.Comment: 20 page
- …