A Remark About Algebraicity in Complete Partial Orders
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Scott Spaces and the Dcpo Category
SCOTT SPACES AND THE DCPO CATEGORY JORDAN BROWN Abstract. Directed-complete partial orders (dcpo’s) arise often in the study of λ-calculus. Here we investigate certain properties of dcpo’s and the Scott spaces they induce. We introduce a new construction which allows for the canonical extension of a partial order to a dcpo and give a proof that the dcpo introduced by Zhao, Xi, and Chen is well-filtered. Contents 1. Introduction 1 2. General Definitions and the Finite Case 2 3. Connectedness of Scott Spaces 5 4. The Categorical Structure of DCPO 6 5. Suprema and the Waybelow Relation 7 6. Hofmann-Mislove Theorem 9 7. Ordinal-Based DCPOs 11 8. Acknowledgments 13 References 13 1. Introduction Directed-complete partially ordered sets (dcpo’s) often arise in the study of λ-calculus. Namely, they are often used to construct models for λ theories. There are several versions of the λ-calculus, all of which attempt to describe the ‘computable’ functions. The first robust descriptions of λ-calculus appeared around the same time as the definition of Turing machines, and Turing’s paper introducing computing machines includes a proof that his computable functions are precisely the λ-definable ones [5] [8]. Though we do not address the λ-calculus directly here, an exposition of certain λ theories and the construction of Scott space models for them can be found in [1]. In these models, computable functions correspond to continuous functions with respect to the Scott topology. It is thus with an eye to the application of topological tools in the study of computability that we investigate the Scott topology. -
Right Ideals of a Ring and Sublanguages of Science
RIGHT IDEALS OF A RING AND SUBLANGUAGES OF SCIENCE Javier Arias Navarro Ph.D. In General Linguistics and Spanish Language http://www.javierarias.info/ Abstract Among Zellig Harris’s numerous contributions to linguistics his theory of the sublanguages of science probably ranks among the most underrated. However, not only has this theory led to some exhaustive and meaningful applications in the study of the grammar of immunology language and its changes over time, but it also illustrates the nature of mathematical relations between chunks or subsets of a grammar and the language as a whole. This becomes most clear when dealing with the connection between metalanguage and language, as well as when reflecting on operators. This paper tries to justify the claim that the sublanguages of science stand in a particular algebraic relation to the rest of the language they are embedded in, namely, that of right ideals in a ring. Keywords: Zellig Sabbetai Harris, Information Structure of Language, Sublanguages of Science, Ideal Numbers, Ernst Kummer, Ideals, Richard Dedekind, Ring Theory, Right Ideals, Emmy Noether, Order Theory, Marshall Harvey Stone. §1. Preliminary Word In recent work (Arias 2015)1 a line of research has been outlined in which the basic tenets underpinning the algebraic treatment of language are explored. The claim was there made that the concept of ideal in a ring could account for the structure of so- called sublanguages of science in a very precise way. The present text is based on that work, by exploring in some detail the consequences of such statement. §2. Introduction Zellig Harris (1909-1992) contributions to the field of linguistics were manifold and in many respects of utmost significance. -
Contents 3 Homomorphisms, Ideals, and Quotients
Ring Theory (part 3): Homomorphisms, Ideals, and Quotients (by Evan Dummit, 2018, v. 1.01) Contents 3 Homomorphisms, Ideals, and Quotients 1 3.1 Ring Isomorphisms and Homomorphisms . 1 3.1.1 Ring Isomorphisms . 1 3.1.2 Ring Homomorphisms . 4 3.2 Ideals and Quotient Rings . 7 3.2.1 Ideals . 8 3.2.2 Quotient Rings . 9 3.2.3 Homomorphisms and Quotient Rings . 11 3.3 Properties of Ideals . 13 3.3.1 The Isomorphism Theorems . 13 3.3.2 Generation of Ideals . 14 3.3.3 Maximal and Prime Ideals . 17 3.3.4 The Chinese Remainder Theorem . 20 3.4 Rings of Fractions . 21 3 Homomorphisms, Ideals, and Quotients In this chapter, we will examine some more intricate properties of general rings. We begin with a discussion of isomorphisms, which provide a way of identifying two rings whose structures are identical, and then examine the broader class of ring homomorphisms, which are the structure-preserving functions from one ring to another. Next, we study ideals and quotient rings, which provide the most general version of modular arithmetic in a ring, and which are fundamentally connected with ring homomorphisms. We close with a detailed study of the structure of ideals and quotients in commutative rings with 1. 3.1 Ring Isomorphisms and Homomorphisms • We begin our study with a discussion of structure-preserving maps between rings. 3.1.1 Ring Isomorphisms • We have encountered several examples of rings with very similar structures. • For example, consider the two rings R = Z=6Z and S = (Z=2Z) × (Z=3Z). -
An Outline of Algebraic Set Theory
An Outline of Algebraic Set Theory Steve Awodey Dedicated to Saunders Mac Lane, 1909–2005 Abstract This survey article is intended to introduce the reader to the field of Algebraic Set Theory, in which models of set theory of a new and fascinating kind are determined algebraically. The method is quite robust, admitting adjustment in several respects to model different theories including classical, intuitionistic, bounded, and predicative ones. Under this scheme some familiar set theoretic properties are related to algebraic ones, like freeness, while others result from logical constraints, like definability. The overall theory is complete in two important respects: conventional elementary set theory axiomatizes the class of algebraic models, and the axioms provided for the abstract algebraic framework itself are also complete with respect to a range of natural models consisting of “ideals” of sets, suitably defined. Some previous results involving realizability, forcing, and sheaf models are subsumed, and the prospects for further such unification seem bright. 1 Contents 1 Introduction 3 2 The category of classes 10 2.1 Smallmaps ............................ 12 2.2 Powerclasses............................ 14 2.3 UniversesandInfinity . 15 2.4 Classcategories .......................... 16 2.5 Thetoposofsets ......................... 17 3 Algebraic models of set theory 18 3.1 ThesettheoryBIST ....................... 18 3.2 Algebraic soundness of BIST . 20 3.3 Algebraic completeness of BIST . 21 4 Classes as ideals of sets 23 4.1 Smallmapsandideals . .. .. 24 4.2 Powerclasses and universes . 26 4.3 Conservativity........................... 29 5 Ideal models 29 5.1 Freealgebras ........................... 29 5.2 Collection ............................. 30 5.3 Idealcompleteness . .. .. 32 6 Variations 33 References 36 2 1 Introduction Algebraic set theory (AST) is a new approach to the construction of models of set theory, invented by Andr´eJoyal and Ieke Moerdijk and first presented in [16]. -
A New Proof of the Completeness of the Lukasiewicz Axioms^)
A NEW PROOF OF THE COMPLETENESS OF THE LUKASIEWICZ AXIOMS^) BY C. C. CHANG The purpose of this note is to provide a new proof for the completeness of the Lukasiewicz axioms for infinite valued propositional logic. For the existing proof of completeness and a history of the problem in general we refer the readers to [l; 2; 3; 4]. The proof as was given in [4] was essentially metamathematical in nature; the proof we offer here is essentially algebraic in nature, which, to some extent, justifies the program initiated by the author in [2]. In what follows we assume thorough familiarity with the contents of [2] and adopt the notation and terminology of [2]. The crux of this proof is con- tained in the following two observations: Instead of using locally finite MV- algebras as the basic building blocks in the structure theory of MV-algebras, we shall use linearly ordered ones. The one-to-one correspondence between linearly ordered MV-algebras and segments of ordered abelian groups enables us to make use of some known results in the first-order theory of ordered abelian groups(2). We say that P is a prime ideal of an MV-algebra A if, and only if, (i) P is an ideal of A, and (ii) for each x, yEA, either xyEP or xyEP- Lemma 1. If P is a prime ideal of A, then A/P is a linearly ordered MV- algebra. Proof. By 3.11 of [2], we have to prove that given x/P and y/P, either x/P^y/P or y/P^x/P. -
Lattice Theory Lecture 2 Distributive Lattices
Lattice Theory Lecture 2 Distributive lattices John Harding New Mexico State University www.math.nmsu.edu/∼JohnHarding.html [email protected] Toulouse, July 2017 Distributive lattices Distributive law for all x; y; z x ∨ (y ∧ z) = (x ∨ y) ∧ (x ∨ z) Modular law if x ≤ z then x ∨ (y ∧ z) = (x ∨ y) ∧ (x ∨ z) Definition The lattices M5 and N5 are as follows: z x y z y x M5 N5 Note M5 is Modular, not distributive, and N5 is Non-modular. Both have 5 elements. 2 / 44 Recognizing distributive lattices Theorem Let L be a lattice. 1. L is modular iff N5 is not a sublattice of L 2. L is distributive iff neither M5; N5 is a sublattice of L Proof The \⇒" direction of each is obvious. For 1 \⇐" if L is not modular, there are x < z with x ∨ (y ∧ z) < (x ∨ y) ∧ (x ∨ z) (why?) Then the following is a sublattice of L. x ∨ y x y z y ( ∨ ) ∧ x ∨ (y ∧ z) y ∧ z 3 / 44 Exercise Give the details that the figure on the previous page is a sublattice. Do the 2 \⇐" direction. The lattice N5 is \projective" in lattices, meaning that if L is a lattice and f ∶ L → N5 is an onto lattice homomorphism, then there is a one-one lattice homomorphism g ∶ N5 → L with f ○ g = id. 4 / 44 Complements Definition Elements x; y of a bounded lattice L are complements if x ∧ y = 0 and x ∨ y = 1. In general, an element might have no complements, or many. 5 / 44 Complements Theorem In a bounded distributive lattice, an element has at most one complement. -
Maximal Orders
MAXIMAL ORDERS BY MAURICE AUSLANDER AND OSCAR GOLDMAN(') Introduction. This paper is about the structure theory of maximal orders in two situations: over Dedekind rings in arbitrary simple algebras and over regular domains in full matrix algebras. By an order over an integrally closed noetherian domain R we mean a subring A of a central simple algebra 2 over the quotient field K of R such that A is a finitely generated i?-module which spans 2 over K. An order A in the simple algebra 2 is said to be maximal if A if not properly contained in any order of 2. The classical argument which shows that over a Dedekind ring every order is contained in a maximal one [6, p. 70 ] is equally valid for arbitrary integrally closed noetherian domains. After a preliminary study of maximal orders in general, we concentrate on maximal orders over discrete rank one valuation rings. The main results in this situation are as follows: all the maximal orders in a fixed simple algebra are conjugate, each is a principal ideal ring and is a full matrix alge- bra over a maximal order in a division algebra. Thus the theory of maximal orders over an arbitrary discrete rank one valuation ring is almost identical with the classical theory in which the valuation ring is assumed complete [6, Chapter VI]. A standard localization argument enables one to conclude that a maximal order over a Dedekind ring is the ring of endomorphisms of a finitely generated projective module over a maximal order in a division alge- bra. -
Introducing Boolean Semilattices Clifford Bergman Iowa State University, [email protected]
Mathematics Publications Mathematics 3-21-2018 Introducing Boolean Semilattices Clifford Bergman Iowa State University, [email protected] Follow this and additional works at: https://lib.dr.iastate.edu/math_pubs Part of the Algebra Commons, and the Logic and Foundations Commons The ompc lete bibliographic information for this item can be found at https://lib.dr.iastate.edu/ math_pubs/195. For information on how to cite this item, please visit http://lib.dr.iastate.edu/ howtocite.html. This Book Chapter is brought to you for free and open access by the Mathematics at Iowa State University Digital Repository. It has been accepted for inclusion in Mathematics Publications by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Introducing Boolean Semilattices Abstract We present and discuss a variety of Boolean algebras with operators that is closely related to the variety generated by all complex algebras of semilattices. We consider the problem of finding a generating set for the variety, representation questions, and axiomatizability. Several interesting subvarieties are presented. We contrast our results with those obtained for a number of other varieties generated by complex algebras of groupoids. Keywords Boolean algebra, BAO, semilattice, Boolean semilattice, Boolean groupoid, canonical extension, equationally definable principal congruence Disciplines Algebra | Logic and Foundations | Mathematics Comments This is a manuscript of a chapter from Bergman C. (2018) Introducing Boolean Semilattices. In: Czelakowski J. (eds) Don Pigozzi on Abstract Algebraic Logic, Universal Algebra, and Computer Science. Outstanding Contributions to Logic, vol 16. Springer, Cham. doi: 10.1007/978-3-319-74772-9_4. -
The Different Ideal
THE DIFFERENT IDEAL KEITH CONRAD 1. Introduction The discriminant of a number field K tells us which primes p in Z ramify in OK : the prime factors of the discriminant. However, the way we have seen how to compute the discriminant doesn't address the following themes: (a) determine which prime ideals in OK ramify (that is, which p in OK have e(pjp) > 1 rather than which p have e(pjp) > 1 for some p), (b) determine the multiplicity of a prime in the discriminant. (We only know the mul- tiplicity is positive for the ramified primes.) Example 1.1. Let K = Q(α), where α3 − α − 1 = 0. The polynomial T 3 − T − 1 has discriminant −23, which is squarefree, so OK = Z[α] and we can detect how a prime p 3 factors in OK by seeing how T − T − 1 factors in Fp[T ]. Since disc(OK ) = −23, only the prime 23 ramifies. Since T 3−T −1 ≡ (T −3)(T −10)2 mod 23, (23) = pq2. One prime over 23 has multiplicity 1 and the other has multiplicity 2. The discriminant tells us some prime over 23 ramifies, but not which ones ramify. Only q does. The discriminant of K is, by definition, the determinant of the matrix (TrK=Q(eiej)), where e1; : : : ; en is an arbitrary Z-basis of OK . By a finer analysis of the trace, we will construct an ideal in OK which is divisible precisely by the ramified primes in OK . This ideal is called the different ideal. (It is related to differentiation, hence the name I think.) In the case of Example 1.1, for instance, we will see that the different ideal is q, so the different singles out the particular prime over 23 that ramifies. -
Ultrafilters on Ω—Their Ideals and Their Cardinal Characteristics
TRANSACTIONS OF THE AMERICAN MATHEMATICAL SOCIETY Volume 351, Number 7, Pages 2643{2674 S 0002-9947(99)02257-6 Article electronically published on March 8, 1999 ULTRAFILTERS ON ω|THEIR IDEALS AND THEIR CARDINAL CHARACTERISTICS JORG¨ BRENDLE AND SAHARON SHELAH Abstract. For a free ultrafilter on ! we study several cardinal character- istics which describe part of theU combinatorial structure of . We provide various consistency results; e.g. we show how to force simultaneouslyU many characters and many π–characters. We also investigate two ideals on the Baire space !! naturally related to and calculate cardinal coefficients of these ideals in terms of cardinal characteristicsU of the underlying ultrafilter. Introduction Let be a non–principal ultrafilter on the natural numbers ω. Recall that is a P {pointU iff for all countable there is U with U A being finite forU all A . is said to be rapid iffA⊆U for all f ωω there∈U is U \ with U f(n) n ∈A U ∈ ∈U | ∩ |≤ for all n ω. is called Ramsey iff given any partition An; n ω of ω,there ∈ U h ∈ i is either n ω with An or U with An U 1 for all n ω.Itis well–known∈ (and easily seen)∈U that Ramsey∈U ultrafilters| ∩ are|≤ both rapid and∈P –point. With we can associate ideals on the real numbers (more exactly, on the Baire space ωωU) in various ways. One way of doing this results in the well–known ideal r0 of Ramsey null sets with respect to (see 2 for the definition). Another, lessU known, ideal related to was introducedU by§ Louveau in [Lo] and shown to coincide with both the meagerU and the nowhere dense ideals on ωω with respect to a topology somewhat finer than the standard topology (see 3 for details). -
Arxiv:1805.07000V1 [Math.LO] 18 May 2018 Mlettosddideal, Sided Two Smallest { Endby Defined Scniuu.Given Continuous
FACTORING A MINIMAL ULTRAFILTER INTO A THICK PART AND A SYNDETIC PART WILL BRIAN AND NEIL HINDMAN Abstract. Let S be an infinite discrete semigroup. The operation on S extends uniquely to the Stone-Cechˇ compactification βS making βS a compact right topological semigroup with S contained in its topological center. As such, βS has a smallest two sided ideal, K(βS). An ultrafilter p on S is minimal if and only if p ∈ K(βS). We show that any minimal ultrafilter p factors into a thick part and a syndetic part. That is, there exist filters F and G such that F consists only of thick sets, G consists only of syndetic sets, and p is the unique ultrafilter containing F∪G. b b Letting L = F and C = G, the sets of ultrafilters containing F and G respectively, we have that L is a minimal left ideal of βS, C meets every minimal left ideal of βS in exactly one point, and L ∩ C = {p}. We show further that K(βS) can be partitioned into relatively closed sets, each of which meets each minimal left ideal in exactly one point. With some weak cancellation assumptions on S, one has also that ∗ for each minimal ultrafilter p, S \ {p} is not normal. In particular, if p is a member of either of the disjoint sets K(βN, +) or K(βN, ·), then ∗ N \ {p} is not normal. 1. Introduction Throughout this paper S will denote an infinite discrete semigroup with operation ·. The Stone-Cechˇ compactification βS of S is the set of ultrafilters on S, with the principal ultrafilters being identified with the points of S. -
Ideal Lattices and the Structure of Rings(J)
IDEAL LATTICES AND THE STRUCTURE OF RINGS(J) BY ROBERT L. BLAIR It is well known that the set of all ideals(2) of a ring forms a complete modular lattice with respect to set inclusion. The same is true of the set of all right ideals. Our purpose in this paper is to consider the consequences of imposing certain additional restrictions on these ideal lattices. In particular, we discuss the case in which one or both of these lattices is complemented, and the case in which one or both is distributive. In §1 two strictly lattice- theoretic results are noted for the sake of their application to the comple- mented case. In §2 rings which have a complemented ideal lattice are con- sidered. Such rings are characterized as discrete direct sums of simple rings. The structure space of primitive ideals of such rings is also discussed. In §3 corresponding results are obtained for rings whose lattice of right ideals is complemented. In particular, it is shown that a ring has a complemented right ideal lattice if and only if it is isomorphic with a discrete direct sum of quasi-simple rings. The socle [7](3) and the maximal regular ideal [5] are discussed in connection with such rings. The effect of an identity element is considered in §4. In §5 rings with distributive ideal lattices are considered and still another variant of regularity [20] is introduced. It is shown that a semi-simple ring with a distributive right ideal lattice is isomorphic with a subdirect sum of division rings.