The main result of this paper is the following theorem: a closure space X has an , , Q-regular base of the power iff X is Q-embeddable in It is a generalization of the following theorems:(i) Stone representation theorem for distributive lattices ( = 0, = , Q = ), (ii) universality of the Alexandroff's cube for T 0-topological spaces ( = , = , Q = 0), (iii) universality of the closure space of filters in the (...) lattice of all subsets for , -closure spaces (Q = 0). By this theorem we obtain some characterizations of the closure space given by the consequence operator for the classical propositional calculus over a formalized language of the zero order with the set of propositional variables of the power . In particular we prove that a countable closure space X is embeddable with finite disjunctions preserved into F iff X is a consistent closure space satisfying the compactness theorem and X contains a 0, -base consisting of -prime sets. (shrink)

This paper is closely related to investigations of abstract properties of basic logical notions expressible in terms of closure spaces as they were begun by A. Tarski (see [6]). We shall prove many properties of -conjunctive closure spaces (X is -conjunctive provided that for every two elements of X their conjunction in X exists). For example we prove the following theorems:1. For every closed and proper subset of an -conjunctive closure space its interior is empty (...) (i.e. it is a boundary set). 2. If X is an -conjunctive closure space which satisfies the -compactness theorem and [X] is a meet-distributive semilattice (see [3]), then the lattice of all closed subsets in X is a Heyting lattice. 3. A closure space is linear iff it is an -conjunctive and topological space. 4. Every continuous function preserves all conjunctions. (shrink)

We give an idea of uniform approach to the problem of characterization of absolute extensors for categories of topological spaces [21], closure spaces [15], Boolean algebras [22], and distributive lattices [4]. In this characterization we use the notion of retract of the closure space of filters in the lattice of all subsets.

In this paper we show that some standard topological constructions may be fruitfully used in the theory of closure spaces (see [5], [4]). These possibilities are exemplified by the classical theorem on the universality of the Alexandroff's cube for T 0-closure spaces. It turns out that the closure space of all filters in the lattice of all subsets forms a generalized Alexandroff's cube that is universal for T 0-closure spaces. By this theorem we (...) obtain the following characterization of the consequence operator of the classical logic: If is a countable set and C: P() P() is a closure operator on X, then C satisfies the compactness theorem iff the closure space ,C is homeomorphically embeddable in the closure space of the consequence operator of the classical logic.We also prove that for every closure space X with a countable base such that the cardinality of X is not greater than 2 there exists a subset X of irrationals and a subset X of the Cantor's set such that X is both a continuous image of X and a continuous image of X. (shrink)

Closure spaces are generalizations of topological spaces, in which the Intersection of two open sets need not be open. The considered logic is related to closure spaces just as the standard logic S4 to topological ones. After describing basic properties of the logic we consider problems of representation of Lindenbaum algebras with some uncountable sets of infinite joins and meets, a notion of equality and a meaning of quantifiers. Results are extended onto the standard logic (...) S4 and they are valid also for some other standard modal logics. (shrink)

Closure space has been proven to be a useful tool to restructure lattices and various order structures. This paper aims to provide an approach to characterizing domains by means of closure spaces. The notion of an interpolative generalized closure space is presented and shown to generate exactly domains, and the notion of an approximable mapping between interpolative generalized closure spaces is identified to represent Scott continuous functions between domains. These produce a category equivalent to (...) that of domains with Scott continuous functions. Meanwhile, some important subclasses of domains are discussed, such as algebraic domains, _L_-domains, bounded-complete domains, and continuous lattices. Conditions are presented which, when fulfilled by an interpolative generalized closure space, make the generated domain fulfill some restrictive conditions. (shrink)

The first order modal logic of closure spaces belongs to the class of equationally definable standard modal logics . One can say, it satisfies no version of the deduction lemma. Nevertheless the Robinson and Beth theorems can be proved by means of an interpretation of modal theories in classical ones. LCS is described in [1], [2], [3], [4]. The logics obtained by adjoining axioms of quasi-equality or of equality to LCS are denoted by LCSQE and LCSE.

In his logical papers, Leo Esakia studied corresponding ordered topological spaces and order-preserving mappings. Similar spaces and mappings appear in many other application areas such the analysis of causality in space-time. It is known that under reasonable conditions, both the topology and the original order relation $${\preccurlyeq}$$ can be uniquely reconstructed if we know the “interior” $${\prec}$$ of the order relation. It is also known that in some cases, we can uniquely reconstruct $${\prec}$$ (and hence, topology) from $${\preccurlyeq}$$. (...) In this paper, we show that, in general, under reasonable conditions, the open order $${\prec}$$ (and hence, the corresponding topology) can be uniquely determined from its closure $${\preccurlyeq}$$. (shrink)

Since the beginning of the current COVID-19 pandemic, specialists were concerned about the potential detrimental effects of physical distancing measures on well-being. Loneliness has been underscored as one of the most critical ones given the wide range of mental and physical health problems associated with it. Unlike social isolation, loneliness does not depend on social network size, so it can be experienced even if surrounded by others, or not be experienced at all even if one is alone. In this article, (...) I propose that the feeling of loneliness might result from a closure in a person’s affordance space, i.e., in the whole range of affordances that might stand out as relevant to an individual with a particular repertoire of habits and embedded within certain sociocultural practices. I will explore three possible sources of this closure during the current pandemic, as well as some ways in which people coped with loneliness. (shrink)

“An epidemic has a dramaturgic form,” wrote Charles Rosenberg in 1989, “Epidemics start at a moment in time, proceed on a stage limited in space and duration, following a plot line of increasing and revelatory tension, move to a crisis of individual and collective character, then drift towards closure.” Rosenberg's dramaturgic description has become an important starting point for critical studies of epidemic endings (Vargha, 2016; Greene & Vargha, 2020; Charters & Heitman, 2021) that, rightly, criticize this structure for (...) its neatness and its linearity. In this article, I want to nuance these criticisms by distinguishing between the term Rosenberg uses, “closure,” and its implicature, “ending.” I aim to show how many of the complications ensuing between the different forms of ending imagined may well be resolved by assessing whether they bring closure or not. (shrink)

It is well known that, in a topological space, the open sets can be characterized using ?lter convergence. In ZF , we cannot replace filters by ultrafilters. It is proven that the ultra?lter convergence determines the open sets for every topological space if and only if the Ultrafilter Theorem holds. More, we can also prove that the Ultra?lter Theorem is equivalent to the fact that uX = kX for every topological space X, where k is the usual Kuratowski closure (...) operator and u is the Ultra?lter Closure with uX := {x ∈ X: [U converges to x and A ∈ U ]}. However, it is possible to built a topological space X for which uX ≠ kX, but the open sets are characterized by the ultra?lter convergence. To do so, it is proved that if every set has a free ultra?lter, then the Axiom of Countable Choice holds for families of non-empty finite sets. It is also investigated under which set theoretic conditions the equality u = k is true in some subclasses of topological spaces, such as metric spaces, second countable T0-spaces or {ℝ}. (shrink)

In a finitary closure space, irreducible sets behave like two-valued models, with membership playing the role of satisfaction. If f is a function on such a space and the membership of in an irreducible set is determined by the presence or absence of the inputs in that set, then f is a kind of truth function. The existence of some of these truth functions is enough to guarantee that every irreducible set is maximally consistent. The closure space is (...) then said to be expressive. This paper identifies the two-valued truth functional conditions that guarantee expressiveness. (shrink)

2Public space is an old habit. The words public space are deceptive; when I hear the words, when I say the words, I’m forced to have an image of a physical place I can point to and be in. I should be thinking only of a condition; but, instead, I imagine an architectural type, and I think of a piazza, or a town square, or a city commons. Public space, I assume, without thinking about it, is a place where the (...) public gathers. The public gathers in two kinds of spaces. The first is a space that is public, a place where the public gathers because it has a right to the place; the second is a space that is made public, a place where the public gathers precisely because it doesn’t have the right—a place made public by force.3In the space that is public, the public whose space this is has agreed to be a public; these are people “in the form of the city,” they are public when they act “in the name of the city.” They “own” the city only in quotes. The establishment of certain space in the city as “public” is a reminder, a warning, that the rest of the city isn’t public. New York doesn’t belong to us, and neither does Paris, and neither does Des Moines. Setting up a public space means setting aside a public space. Public space is a place in the middle of the city but isolated from the city. Public space is the piazza, an open space separated from the closure of alleys and dead ends; public space is the piazza, a space in the light, away from the plots and conspiracies in dark smokey rooms. Vit Acconci’s latest show, entitled “Public Places,” was held in 1988 at the Museum of Modern Art, New York. He is currently at work on a park in Detroit, a pedestrian mall in Baltimore, and a housing project in Regensburg, Germany. (shrink)

And yet, in these very texts Sallis identifies outbreaks of spacing that would disrupt the tranquil space of reason. Rather than closure, he finds an opening of reason to imagination.

In the categorical approach to the foundations of quantum theory, one begins with a symmetric monoidal category, the objects of which represent physical systems, and the morphisms of which represent physical processes. Usually, this category is taken to be at least compact closed, and more often, dagger compact, enforcing a certain self-duality, whereby preparation processes (roughly, states) are interconvertible with processes of registration (roughly, measurement outcomes). This is in contrast to the more concrete “operational” approach, in which the states and (...) measurement outcomes associated with a physical system are represented in terms of what we here call a convex operational model: a certain dual pair of ordered linear spaces–generally, not isomorphic to one another. On the other hand, state spaces for which there is such an isomorphism, which we term weakly self-dual, play an important role in reconstructions of various quantum-information theoretic protocols, including teleportation and ensemble steering. In this paper, we characterize compact closure of symmetric monoidal categories of convex operational models in two ways: as a statement about the existence of teleportation protocols, and as the principle that every process allowed by that theory can be realized as an instance of a remote evaluation protocol—hence, as a form of classical probabilistic conditioning. In a large class of cases, which includes both the classical and quantum cases, the relevant compact closed categories are degenerate, in the weak sense that every object is its own dual. We characterize the dagger-compactness of such a category (with respect to the natural adjoint) in terms of the existence, for each system, of a symmetric bipartite state, the associated conditioning map of which is an isomorphism. (shrink)

The Baire algebra of a topological space X is the quotient of the algebra of all subsets of X modulo the meager sets. We show that this Boolean algebra can be endowed with a natural closure operator, resulting in a closure algebra which we denote $\mathbf {Baire}(X)$. We identify the modal logic of such algebras to be the well-known system $\mathsf {S5}$, and prove soundness and strong completeness for the cases where X is crowded and either completely metrizable (...) and continuum-sized or locally compact Hausdorff. We also show that every extension of $\mathsf {S5}$ is the modal logic of a subalgebra of $\mathbf {Baire}(X)$, and that soundness and strong completeness also holds in the language with the universal modality. (shrink)

When we interpret modal ◊ as the limit point operator of a topological space, the Gödel-Löb modal system GL defines the class Scat of scattered spaces. We give a partition of Scat into α-slices S α , where α ranges over all ordinals. This provides topological completeness and definability results for extensions of GL. In particular, we axiomatize the modal logic of each ordinal α, thus obtaining a simple proof of the Abashidze–Blass theorem. On the other hand, when we (...) interpret ◊ as closure in a topological space, the Grzegorczyk modal system Grz defines the class HI of hereditarily irresolvable spaces. We also give a partition of HI into α-slices H α , where α ranges over all ordinals. For a subset A of a hereditarily irresolvable space X and an ordinal α, we introduce the α-representation of A, give an axiomatization of the α-representation of A, and characterize H α in terms of α-representations. We prove that ${X \in {\bf H}_{1}}$ iff X is submaximal. For a positive integer n, we generalize the notion of a submaximal space to that of an n-submaximal space, and prove that ${X \in {\bf H}_{n}}$ iff X is n-submaximal. This provides topological completeness and definability results for extensions of Grz. We show that the two partitions are related to each other as follows. For a successor ordinal α = β + n, with β a limit ordinal and n a positive integer, we have ${{\bf H}_{\alpha} \cap {\bf Scat} = {\bf S}_{\beta+2n-1} \cup {\bf S}_{\beta+2n}}$ , and for a limit ordinal α, we have ${{\bf H}_{\alpha} \cap {\bf Scat} = {\bf S}_{\alpha}}$ . As a result, we obtain full and faithful translations of ordinal complete extensions of Grz into ordinal complete extensions of GL, thus generalizing the Kuznetsov–Goldblatt–Boolos theorem. (shrink)

Review of the paper mentioned in the title.

COVID-19 modifies a number of social behaviors and standards that we have been following. In slum research, the multifarious issues posed by COVID-19 are not limited to the increased disadvantages of slum inhabitants, but also to the closure of slums as a physical space conducive to understanding the slum dwellers’ plight. Their voices are silenced at a time when their narratives are critical for developing policies and initiatives to address their predicament. In this regard, the article will examine Merleau-Ponty’s (...) concept of space and then utilize it to create an ethics of space, which is crucial in establishing the viability of virtual space as a creative space that may be used in lieu of traditional slum research. Finally, I discuss the advantages of using virtual space as an alternate space in slum research and how the study might be expanded in the post-COVID era. (shrink)

It is a classic result (McKinsey & Tarski, 1944; Rasiowa & Sikorski, 1963) that if we interpret modal diamond as topological closure, then the modal logic of any dense-in-itself metric space is the well-known modal system S4. In this paper, as a natural follow-up, we study the modal logic of an arbitrary metric space. Our main result establishes that modal logics arising from metric spaces form the following chain which is order-isomorphic (with respect to the ⊃ relation) to (...) the ordinalω+ 3:$S4.Gr{z_1} \supset S4.Gr{z_2} \supset S4.Gr{z_3} \supset \cdots \,S4.Grz \supset S4.1 \supset S4.$It follows that the modal logic of an arbitrary metric space is finitely axiomatizable, has the finite model property, and hence is decidable. (shrink)

We show that considerable sets of positive linear operators namely their extensions as closures, adjoints or Friedrichs positive self-adjoint extensions form operator (generalized) effect algebras. Moreover, in these cases the partial effect algebraic operation of two operators coincides with usual sum of operators in complex Hilbert spaces whenever it is defined. These sets include also unbounded operators which play important role of observables (e.g., momentum and position) in the mathematical formulation of quantum mechanics.

Let W be a recursively enumerable vector space over a recursive ordered field. We show the Turing equivalence of the following sets: the set of all tuples of vectors in W which are linearly dependent; the set of all tuples of vectors in W whose convex closures contain the zero vector; and the set of all pairs of tuples in W such that the convex closure of X intersects the convex closure of Y. We also form the analogous (...) sets consisting of tuples with given numbers of elements, and prove similar results on the Turing equivalence of these. (shrink)

Picking up the question of what FLaK might be, this editorial considers the relationship between openness and closure in feminist legal studies. How do we draw on feminist struggles for openness in common resources, from security to knowledge, as we inhabit a compromised space in commercial publishing? We think about this first in relation to the content of this issue: on image-based abuse continuums, asylum struggles, trials of protestors, customary justice, and not-so-timely reparations. Our thoughts take us through the (...) different ways that openness and closure work in struggles against violence, cruel welcomes, and re-arrangements of code and custom. Secondly, we share some reflections on methodological openness and closure as the roundtable conversation on asylum, and the interview with Riles, remind us of #FLaK2016 and its method of scattering sources as we think about how best to mix knowledges. Thirdly, prompted by the FLaK kitchen table conversations on openness, publishing and ‘getting the word out’, we respond to Kember’s call to ‘open up open access’. We explain the different current arrangements for opening up FLS content and how green open access, the sharedit initiative, author request and publisher discretion present alternatives to gold open access. Finally drawing on Franklin and Spade, we show how there are a range of ‘wench tactics’—adapting gifts, stalling and resting—which we deploy as academic editors who are trying to have an impact on the access, use and circulation of our journal, even though we do not own the journal we edit. These wench tactics are alternatives to the more obvious or reported tactic of resignation, or withdrawing academic labour from editing and reviewing altogether. They help us think about brewing editorial time, what ambivalence over our 25th birthday might mean, and how to inhabit painful places. In this, we respond in our own impure, compromised way to da Silva’s call not to forget the native and slave as we do FLaK, and repurpose shrapnel, in our common commitments. (shrink)

As they make their way through Louis Althusser’s and Jacques Derrida’s texts, readers will cross innumerable curtains – ‘the words and things’, as Derrida says, as many fabrics of traces. These curtains open onto a multiplicity of scenes and mises en scène, performances, roles, rituals, actors, plays – thus unfolding the space of a certain theatricality. This essay traces Althusser’s and Derrida’s respective deployments of the theatrical motif. In his theoretical writings, Althusser’s theatrical dispositive aims to designate the practical and (...) material dimension of the scenes of ideology, materially enacted through roleplays, performances, acts, or discourses. At the horizon: a scientific discourse on ideology or, later, a strategic intervention in the class struggle. This scientific and/or strategic orientation echoes Althusser’s definition of materialism: ‘no more storytelling’. But Derrida’s ‘closure of representation’ reminds us that there’s no presence – even the most ‘material’ – no ‘truth’ or ‘correctness’ – in theoretical or strategic terms – without effects of re-presentation, differential repetition, narrative reconstruction: theatricality and materiality suppose a force of resistance, a secret heterogeneity, curtain foldings. Hence the irreducible necessity of reading, storytelling, transformative interpretation. What are the implications for thinking inheritance and debt – for example, the one binding Althusser and Derrida, and us to them? (shrink)

Open peer commentary on the article “Social Autopoiesis?” by Hugo Urrestarazu. Upshot: Social autopoiesis does not operate in physical space and cannot be understood by analyzing cause-effect relationships. Social systems are observing systems operating in the space of meaning. Therefore a validation procedure guided by the classic rules for determining autopoietic systems is misleading. However, the target article clarifies a point of great importance for sociological research: the difference between autopoiesis and autonomy (closure.

This study is concerned with the organisation of gestural phases of non-movement, in particular the prolonged hold and provisional home position, as accountably and in situ produced segments of behaviour. Through fine-grained transcriptions and multimodal analysis of videotaped conversation in natural and everyday settings, it is found that movement phases may be exploited by participants in order to indicate that a pursued trajectory or line of action is maintained, suspended or abandoned. Also, through constant monitoring, participants may adjust the location (...) of non-movement as the interaction unfolds in time. It is argued that various possible locations of non-movement are arranged along a continuum ranging from the space of gesticulation to a relaxed rest position and that these locations reflect various degrees of involvement or claim of speakership in the gesturer. (shrink)

Under the axiom of choice, every first countable space is a Fréchet-Urysohn space. Although, in its absence even ℝ may fail to be a sequential space.Our goal in this paper is to discuss under which set-theoretic conditions some topological classes, such as the first countable spaces, the metric spaces, or the subspaces of ℝ, are classes of Fréchet-Urysohn or sequential spaces.In this context, it is seen that there are metric spaces which are not sequential spaces. (...) This fact raises the question of knowing if the completion of a metric space exists and it is unique. The answer depends on the definition of completion.Among other results it is shown that: every first countable space is a sequential space if and only if the axiom of countable choice holds, the sequential closure is idempotent in ℝ if and only if the axiom of countable choice holds for families of subsets of ℝ, and every metric space has a unique equation image-completion. (shrink)

We consider two topological interpretations of the modal diamond—as the closure operator (C-semantics) and as the derived set operator (d-semantics). We call the logics arising from these interpretations C-logics and d-logics, respectively. We axiomatize a number of subclasses of the class of nodec spaces with respect to both semantics, and characterize exactly which of these classes are modally definable. It is demonstrated that the d-semantics is more expressive than the C-semantics. In particular, we show that the d-logics of (...) the six classes of spaces considered in the paper are pairwise distinct, while the C-logics of some of them coincide. (shrink)

Through contact algebras we study theories of mereotopology in a uniform way that clearly separates mereological from topological concepts. We identify and axiomatize an important subclass of closure mereotopologies called unique closure mereotopologies whose models always have orthocomplemented contact algebras , an algebraic counterpart. The notion of MT-representability, a weak form of spatial representability but stronger than topological representability, suffices to prove that spatially representable complete OCAs are pseudocomplemented and satisfy the Stone identity. Within the resulting class of (...) contact algebras the strength of the algebraic complementation delineates two classes of mereotopology according to the key ontological choice between mereological and topological closure operations. All closure operations are defined mereologically if and only if the corresponding contact algebras are uniquely complemented while topological closure operations highly restrict the contact relation but allow not uniquely complemented and nondistributive contact algebras. Each class contains a single ontologically coherent theory that admits discrete models. (shrink)

Developing a major extractive project requires a long planning horizon from exploration to project development to operation and closure. Calibrating expectations of indigenous communities with such planning horizons can frequently be a challenge for companies and governments. The physical areas where benefits are manifest on indigenous lands versus more indirect benefits that come through the development of the broader tax base or the economy are often not effectively communicated by development planners. This conceptual study will aim to provide guidance (...) on how best to manage expectations in this context through scenarios, geographic information systems techniques, and a more inclusive economic development planning process. (shrink)

A ‘spatial turn’ is observed as taking place across a range of disciplines. This article discusses the relevance of this ‘spatial turn’ to the issue of early school leaving prevention and engagement of marginalised students and their parents within the educational system and other support services. Building on reconceptualisation of an aspect of structural anthropology a specific dynamic spatial interaction between diametric and concentric structures of relation is proposed. Reification is interpreted as involving a diametric space of assumed separation, (...) class='Hi'>closure and mirror image inversions. Concentric relational space as assumed connection and relative openness is a precondition for trust, care and voice. Diametric and concentric spatial features of school and related systems are interrogated for early school leaving issues, such as the importance of relational supports to keep students in the system; the precondition of trust for parental involvement of more marginalised parents, including a lifelong learning and family support aspect; the need to challenge the school as a closed system with reified hierarchies. (shrink)

An exploration of the post-politics of global capitalism in theory and practice Our age is celebrated as the triumph of liberal democracy. Old ideological battles have been decisively resolved in favour of freedom and the market. We are told that we have moved 'beyond left and right'; that we are 'all in this together'. Any remaining differences are to be addressed through expert knowledge, consensual deliberation and participatory governance. Yet the 'end of history' has also been marked by widespread disillusion (...) with mainstream politics and a rise in nationalist and religious fundamentalisms. And now an explosion of popular protests is challenging technocratic regulation and the power of markets in the name of democracy itself. This collection makes sense of this situation by critically engaging with the influential theory of 'the post-political' developed by Chantal Mouffe, Jacques Ranciere, Slavoj Zizek and others. Through a multi-dimensional and fiercely contested assessment of contemporary depoliticisation, The Post-Political and Its Discontents urges us to confront the closure of our political horizons and re-imagine the possibility of emancipatory change. ". (shrink)

The expressive truth functions of two-valued logic have all been identified. This paper begins the task of identifying the expressive truth functions of n-valued logic by characterizing the unary ones. These functions have distinctive algebraic, semantic, and closure-theoretic properties.

In this paper we study an alternative approach to the concept of abstract logic and to connectives in abstract logics. The notion of abstract logic was introduced by Brown and Suszko —nevertheless, similar concepts have been investigated by various authors. Considering abstract logics as intersection structures we extend several notions to their κ -versions, introduce a hierarchy of κ -prime theories, which is important for our treatment of infinite connectives, and study different concepts of κ -compactness. We are particularly interested (...) in non-topped intersection structures viewed as semi-lattices with a minimal meet-dense subset, i.e., with a minimal generator set. We study a chain condition which is sufficient for a minimal generator set, implies compactness of the logic, and in regular logics is equivalent to compactness of the consequence relation together with the existence of a inconsistent set, where κ is the cofinality of the cardinality of the logic. Some of these results are known in a similar form in the context of closure spaces, we give extensions to intersection structures and to big cardinals presenting new proofs based on set-theoretical tools. The existence of a minimal generator set is crucial for our way to define connectives. Although our method can be extended to further non-classical connectives we concentrate here on intuitionistic and infinite ones. Our approach leads us to the concept of the set of complete theories which is stable under all considered connectives and gives rise to the definition of the topological space of the logic. Topological representations of abstract logics by means of this space remain to be further investigated. (shrink)

Define a second order tree to be a map between trees. We show that many properties of ordinary trees have analogs for second order trees. In particular, we show that there is a notion of “definition by recursion on a well-founded second order tree” which generalizes “definition by transfinite recursion”. We then use this new notion of definition by recursion to prove an analog of Lusin’s Separation theorem for closure spaces of global sections of a second order tree.

In the paper [2] the following theorem is shown: Theorem (Th. 3,5, [2]), If =0 or = or , then a closure space X is an absolute extensor for the category of , -closure spaces iff a contraction of X is the closure space of all , -filters in an , -semidistributive lattice.In the case when = and =, this theorem becomes Scott's theorem.

The aim of this paper is to give a general background and a uniform treatment of several notions of mutual interpretability. Sentential calculi are treated as preorders and logical invariants of adjoint situations, i.e. Galois connections are investigated. The class of all sentential calculi is treated as a quasiordered class.Some methods of the axiomatization of the M-counterparts of modal systems are based on particular adjoints. Also, invariants concerning adjoints for calculi with implication are pointed out. Finally, the notion of interpretability (...) is generalized so that it may be applied to closure spaces as well. (shrink)

We show that the Axiom of Choice is equivalent to each of the following statements: A product of closures of subsets of topological spaces is equal to the closure of their product ; A product of complete uniform spaces is complete.

Universality of generalized Alexandroff's cube plays essential role in theory of absolute retracts for the category of , -closure spaces. Alexandroff's cube. is an , -closure space generated by the family of all complete filters. in a lattice of all subsets of a set of power .Condition P(, , ) says that is a closure space of all , -filters in the lattice ( ).

The study of information based on the approach of Shannon was detached from problems of meaning. Also, it did not allow analysis of the structural characteristics of information, nor describe the way structures carry information. An outline of a different theory of information, including its semantics, was earlier proposed by the author. This theory was using closure spaces to model information. In the present paper, structures (called syllogistics) underlying syllogistic reasoning as well as ethnoscientific classifications are identified together (...) with the conditions for the lattice of closed subsets describing information to allow its existence. The structures can be used for logical analysis outside of language at the more general level of information, which in turn can be applied to the description of semantic relations in the context of information. (shrink)

This paper is a continuation of investigations on Galois connections from [1], [3], [10]. It is a continuation of [2]. We have shown many results that link properties of a given closure space with that of the dual space. For example: for every -disjunctive closure space X the dual closure space is topological iff the base of X generated by this dual space consists of the -prime sets in X (Theorem 2). Moreover the characterizations of the satisfiability (...) relation for classical logic are shown. Roughly speaking our main result here is the following: a satisfiability relation in a logic L with, a countable language is a fragment of the classical one iff the compactness theorem for L holds (Theorems 3–8). (shrink)

All spaces are assumed to be separable and metrizable. Consider the following properties of a space X. X is Polish.For every countable crowded Q⊆X\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${Q \subseteq X}$$\end{document} there exists a crowded Q′⊆Q\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${Q'\subseteq Q}$$\end{document} with compact closure.Every closed subspace of X is either scattered or it contains a homeomorphic copy of 2ω\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${2^\omega}$$\end{document}.Every closed subspace (...) of X is a Baire space. While is the well-known property of being completely Baire, properties and have been recently introduced by Kunen, Medini and Zdomskyy, who named them the Miller property and the Cantor-Bendixson property respectively. It turns out that the implications →→→\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${ \rightarrow \rightarrow \rightarrow }$$\end{document} hold for every space X. Furthermore, it follows from a classical result of Hurewicz that all these implications are equivalences if X is coanalytic. Under the axiom of Projective Determinacy, this equivalence result extends to all projective spaces. We will complete the picture by giving a ZFC\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\sf ZFC}$$\end{document} counterexample and a consistent definable counterexample of lowest possible complexity to the implication ←\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${ \leftarrow }$$\end{document} for i=1,2,3\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${i = 1, 2, 3}$$\end{document}. For one of these counterexamples we will need a classical theorem of Martin and Solovay, of which we give a new proof, based on a result of Baldwin and Beaudoin. Finally, using a method of Fischer and Friedman, we will investigate how changing the value of the continuum affects the definability of these counterexamples. Along the way, we will show that every uncountable completely Baire space has size continuum. (shrink)

Coherence-spaces and domains with totality are used to give interpretations of inductively defined types. A category of coherence spaces with totality is defined and the closure of positive inductive type constructors is analysed within this category. Type streams are introduced as a generalisation of types defined by strictly positive inductive definition. A semantical analysis of type streams with continuous recursion theorems is established. A hierarchy of domains with totality defined by positive induction is defined, and density for (...) a sub-hierarchy is proved. (shrink)