Free Boolean algebras with closure operators and a conjecture of Henkin, Monk, and Tarski

2001 ◽  
Vol 38 (1-4) ◽  
pp. 273-278
Author(s):  
I. Németi ◽  
J. X. Madarász
Keyword(s):  
Boolean Algebras ◽  
Cylindric Algebra ◽  
Cylindric Algebras ◽  
Closure Operators ◽  
Finite Dimensional

We characterize the finite-dimensional elements of a free cylindric algebra. This solves Problem 2.10 in [Henkin, Monk, Tarski: Cylindric Algebras, North-Holland, 1971 and 1985]. We generalize the characterization to quasi-varieties of Boolean algebras with op- erators in place of cylindric algebras.

Nonfinitizability of classes of representable cylindric algebras

1969 ◽  
Vol 34 (3) ◽  
pp. 331-343 ◽  
Author(s):  
J. Donald Monk
Keyword(s):  
Predicate Logic ◽  
Infinite Dimension ◽  
Fundamental Result ◽  
Cylindric Algebra ◽  
Cylindric Algebras ◽  
Locally Finite ◽  
First Order ◽  
Alfred Tarski ◽  
Sentential Logic ◽  
Algebraic Counterpart

Cylindric algebras were introduced by Alfred Tarski about 1952 to provide an algebraic analysis of (first-order) predicate logic. With each cylindric algebra one can, in fact, associate a certain, in general infinitary, predicate logic; for locally finite cylindric algebras of infinite dimension the associated predicate logics are finitary. As with Boolean algebras and sentential logic, the algebraic counterpart of completeness is representability. Tarski proved the fundamental result that every locally finite cylindric algebra of infinite dimension is representable.

STONE SPACE OF CYLINDRIC ALGEBRAS AND TOPOLOGICAL MODEL SPACES

2016 ◽  
Vol 81 (3) ◽  
pp. 1069-1086
Author(s):  
CHARLES C. PINTER
Keyword(s):  
Boolean Algebra ◽  
Model Theory ◽  
Representation Theorem ◽  
Stone Space ◽  
Equivalence Relations ◽  
Cylindric Algebra ◽  
Cylindric Algebras ◽  
Locally Finite ◽  
Abstract Model Theory ◽  
Image Position

AbstractThe Stone representation theorem was a milestone for the understanding of Boolean algebras. From Stone’s theorem, every Boolean algebra is representable as a field of sets with a topological structure. By means of this, the structural elements of any Boolean algebra, as well as the relations between them, are represented geometrically and can be clearly visualized. It is no different for cylindric algebras: Suppose that ${\frak A}$ is a cylindric algebra and ${\cal S}$ is the Stone space of its Boolean part. (Among the elements of the Boolean part are the diagonal elements.) It is known that with nothing more than a family of equivalence relations on ${\cal S}$ to represent quantifiers, ${\cal S}$ represents the full cylindric structure just as the Stone space alone represents the Boolean structure. ${\cal S}$ with this structure is called a cylindric space.Many assertions about cylindric algebras can be stated in terms of elementary topological properties of ${\cal S}$. Moreover, points of ${\cal S}$ may be construed as models, and on that construal ${\cal S}$ is called a model space. Certain relations between points on this space turn out to be morphisms between models, and the space of models with these relations hints at the possibility of an “abstract” model theory. With these ideas, a point-set version of model theory is proposed, in the spirit of pointless topology or category theory, in which the central insight is to treat the semantic objects (models) homologously with the corresponding syntactic objects so they reside together in the same space.It is shown that there is a new, purely algebraic way of introducing constants in cylindric algebras, leading to a simplified proof of the representation theorem for locally finite cylindric algebras. Simple rich algebras emerge as homomorphic images of cylindric algebras. The topological version of this theorem is especially interesting: The Stone space of every locally finite cylindric algebra ${\frak A}$ can be partitioned into subspaces which are the Stone spaces of all the simple rich homomorphic images of ${\frak A}$. Each of these images completely determines a model of ${\frak A}$, and all denumerable models of ${\frak A}$ appear in this representation.The Stone space ${\cal S}$ of every cylindric algebra can likewise be partitioned into closed sets which are duals of all the types in ${\frak A}$. This fact yields new insights into miscellaneous results in the model theory of saturated models.

Nonfinitizability of classes of representable polyadic algebras

1969 ◽  
Vol 34 (3) ◽  
pp. 344-352 ◽  
Author(s):  
James S. Johnson
Keyword(s):  
Predicate Logic ◽  
Free Algebras ◽  
Cylindric Algebra ◽  
Cylindric Algebras ◽  
Polyadic Algebras

The notion of polyadic algebra was introduced by Halmos to reflect algebraically the predicate logic without equality. Later Halmos enriched the study with the introduction of the notion of equality. These algebras are very closely related to the cylindric algebras of Tarski. The notion of diagonal free cylindric algebra predates that of cylindric algebra and is also due to Tarski. The theory of diagonal free algebras forms an important fragment of the theories of polyadic and cylindric algebras.

scholarly journals On weak and strong interpolation in algebraic logics

2006 ◽  
Vol 71 (1) ◽  
pp. 104-118 ◽  
Author(s):  
Gábor Sági ◽  
Saharon Shelah
Keyword(s):  
Algebraic Logic ◽  
Amalgamation Property ◽  
Weak Form ◽  
Interpolation Theorem ◽  
Order Logic ◽  
Cylindric Algebras ◽  
First Order ◽  
Finite Dimensional ◽  
Craig’S Interpolation Theorem ◽  
Superamalgamation Property

AbstractWe show that there is a restriction, or modification of the finite-variable fragments of First Order Logic in which a weak form of Craig's Interpolation Theorem holds but a strong form of this theorem does not hold. Translating these results into Algebraic Logic we obtain a finitely axiomatizable subvariety of finite dimensional Representable Cylindric Algebras that has the Strong Amalgamation Property but does not have the Superamalgamation Property. This settles a conjecture of Pigozzi [12].

Copeland algebras

1972 ◽  
Vol 37 (4) ◽  
pp. 646-656 ◽  
Author(s):  
Daniel B. Demaree
Keyword(s):  
Predicate Logic ◽  
Algebraic Logic ◽  
Boolean Algebras ◽  
Primary Concern ◽  
Cylindric Algebras ◽  
First Order ◽  
Polyadic Algebras ◽  
Algebraic Setting ◽  
Finite Set ◽  
Natural Way

It is well known that the laws of logic governing the sentence connectives—“and”, “or”, “not”, etc.—can be expressed by means of equations in the theory of Boolean algebras. The task of providing a similar algebraic setting for the full first-order predicate logic is the primary concern of algebraic logicians. The best-known efforts in this direction are the polyadic algebras of Halmos (cf. [2]) and the cylindric algebras of Tarski (cf. [3]), both of which may be described as Boolean algebras with infinitely many additional operations. In particular, there is a primitive operator, cκ, corresponding to each quantification, ∃υκ. In this paper we explore a version of algebraic logic conceived by A. H. Copeland, Sr., and described in [1], which has this advantage: All operators are generated from a finite set of primitive operations.Following the theory of cylindric algebras, we introduce, in the natural way, the classes of Copeland set algebras (SCpA), representable Copeland algebras (RCpA), and Copeland algebras of formulas. Playing a central role in the discussion is the set, Γ, of all equations holding in every set algebra. The reason for this is that the operations in a set algebra reflect the notion of satisfaction of a formula in a model, and hence an equation expresses the fact that two formulas are satisfied by the same sequences of objects in the model. Thus to say that an equation holds in every set algebra is to assert that a certain pair of formulas are logically equivalent.

The equational theory of CA3 is undecidable

1980 ◽  
Vol 45 (2) ◽  
pp. 311-316 ◽  
Author(s):  
Roger Maddux
Keyword(s):  
Equational Theory ◽  
Cylindric Algebra ◽  
Relation Algebras ◽  
Cylindric Algebras ◽  
3 Dimensional ◽  
First Order ◽  
Equational Theories ◽  
Order Language ◽  
Theoretic Proof

There is no algorithm for determining whether or not an equation is true in every 3-dimensional cylindric algebra. This theorem completes the solution to the problem of finding those values of α and β for which the equational theories of CAα and RCAβ are undecidable. (CAα and RCAβ are the classes of α-dimensional cylindric algebras and representable β-dimensional cylindric algebras. See [4] for definitions.) This problem was considered in [3]. It was known that RCA0 = CA0 and RCA1 = CA1 and that the equational theories of these classes are decidable. Tarski had shown that the equational theory of relation algebras is undecidable and, by utilizing connections between relation algebras and cylindric algebras, had also shown that the equational theories of CAα and RCAβ are undecidable whenever 4 ≤ α and 3 ≤ β. (Tarski's argument also applies to some varieties K ⊆ RCAβ with 3 ≤ β and to any variety K such that RCAα ⊆ K ⊆ CAα and 4 ≤ α.)Thus the only cases left open in 1961 were CA2, RCA2 and CA3. Shortly there-after Henkin proved, in one of Tarski's seminars at Berkeley, that the equational theory of CA2 is decidable, and Scott proved that the set of valid sentences in a first-order language with only two variables is recursive [11]. (For a more model-theoretic proof of Scott's theorem see [9].) Scott's result is equivalent to the decidability of the equational theory of RCA2, so the only case left open was CA3.

scholarly journals Strongly representable atom structures of cylindric algebras

2009 ◽  
Vol 74 (3) ◽  
pp. 811-828 ◽  
Author(s):  
Robin Hirsch ◽  
Ian Hodkinson
Keyword(s):  
Chromatic Number ◽  
Cylindric Algebra ◽  
Cylindric Algebras ◽  
Free Graph ◽  
Complex Algebra

AbstractA cylindric algebra atom structure is said to be strongly representable if all atomic cylindric algebras with that atom structure are representable. This is equivalent to saying that the full complex algebra of the atom structure is a representable cylindric algebra. We show that for any finite n ≥ 3, the class of all strongly representable n-dimensional cylindric algebra atom structures is not closed under ultraproducts and is therefore not elementary.Our proof is based on the following construction. From an arbitrary undirected, loop-free graph Γ, we construct an n-dimensional atom structure , and prove, for infinite Γ, that is a strongly representable cylindric algebra atom structure if and only if the chromatic number of Γ is infinite. A construction of Erdős shows that there are graphs Γk(k < ω) with infinite chromatic number, but having a non-principal ultraproduct ΠDΓk whose chromatic number is just two. It follows that is strongly representable (each k < ω) but is not.

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