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Mathematical Logic. Introduction. by Vilnis Detlovs And
1 Version released: May 24, 2017 Introduction to Mathematical Logic Hyper-textbook for students by Vilnis Detlovs, Dr. math., and Karlis Podnieks, Dr. math. University of Latvia This work is licensed under a Creative Commons License and is copyrighted © 2000-2017 by us, Vilnis Detlovs and Karlis Podnieks. Sections 1, 2, 3 of this book represent an extended translation of the corresponding chapters of the book: V. Detlovs, Elements of Mathematical Logic, Riga, University of Latvia, 1964, 252 pp. (in Latvian). With kind permission of Dr. Detlovs. Vilnis Detlovs. Memorial Page In preparation – forever (however, since 2000, used successfully in a real logic course for computer science students). This hyper-textbook contains links to: Wikipedia, the free encyclopedia; MacTutor History of Mathematics archive of the University of St Andrews; MathWorld of Wolfram Research. 2 Table of Contents References..........................................................................................................3 1. Introduction. What Is Logic, Really?.............................................................4 1.1. Total Formalization is Possible!..............................................................5 1.2. Predicate Languages.............................................................................10 1.3. Axioms of Logic: Minimal System, Constructive System and Classical System..........................................................................................................27 1.4. The Flavor of Proving Directly.............................................................40 -
Sets in Homotopy Type Theory
Predicative topos Sets in Homotopy type theory Bas Spitters Aarhus Bas Spitters Aarhus Sets in Homotopy type theory Predicative topos About me I PhD thesis on constructive analysis I Connecting Bishop's pointwise mathematics w/topos theory (w/Coquand) I Formalization of effective real analysis in Coq O'Connor's PhD part EU ForMath project I Topos theory and quantum theory I Univalent foundations as a combination of the strands co-author of the book and the Coq library I guarded homotopy type theory: applications to CS Bas Spitters Aarhus Sets in Homotopy type theory Most of the presentation is based on the book and Sets in HoTT (with Rijke). CC-BY-SA Towards a new design of proof assistants: Proof assistant with a clear (denotational) semantics, guiding the addition of new features. E.g. guarded cubical type theory Predicative topos Homotopy type theory Towards a new practical foundation for mathematics. I Modern ((higher) categorical) mathematics I Formalization I Constructive mathematics Closer to mathematical practice, inherent treatment of equivalences. Bas Spitters Aarhus Sets in Homotopy type theory Predicative topos Homotopy type theory Towards a new practical foundation for mathematics. I Modern ((higher) categorical) mathematics I Formalization I Constructive mathematics Closer to mathematical practice, inherent treatment of equivalences. Towards a new design of proof assistants: Proof assistant with a clear (denotational) semantics, guiding the addition of new features. E.g. guarded cubical type theory Bas Spitters Aarhus Sets in Homotopy type theory Formalization of discrete mathematics: four color theorem, Feit Thompson, ... computational interpretation was crucial. Can this be extended to non-discrete types? Predicative topos Challenges pre-HoTT: Sets as Types no quotients (setoids), no unique choice (in Coq), .. -
A Taste of Set Theory for Philosophers
Journal of the Indian Council of Philosophical Research, Vol. XXVII, No. 2. A Special Issue on "Logic and Philosophy Today", 143-163, 2010. Reprinted in "Logic and Philosophy Today" (edited by A. Gupta ans J.v.Benthem), College Publications vol 29, 141-162, 2011. A taste of set theory for philosophers Jouko Va¨an¨ anen¨ ∗ Department of Mathematics and Statistics University of Helsinki and Institute for Logic, Language and Computation University of Amsterdam November 17, 2010 Contents 1 Introduction 1 2 Elementary set theory 2 3 Cardinal and ordinal numbers 3 3.1 Equipollence . 4 3.2 Countable sets . 6 3.3 Ordinals . 7 3.4 Cardinals . 8 4 Axiomatic set theory 9 5 Axiom of Choice 12 6 Independence results 13 7 Some recent work 14 7.1 Descriptive Set Theory . 14 7.2 Non well-founded set theory . 14 7.3 Constructive set theory . 15 8 Historical Remarks and Further Reading 15 ∗Research partially supported by grant 40734 of the Academy of Finland and by the EUROCORES LogICCC LINT programme. I Journal of the Indian Council of Philosophical Research, Vol. XXVII, No. 2. A Special Issue on "Logic and Philosophy Today", 143-163, 2010. Reprinted in "Logic and Philosophy Today" (edited by A. Gupta ans J.v.Benthem), College Publications vol 29, 141-162, 2011. 1 Introduction Originally set theory was a theory of infinity, an attempt to understand infinity in ex- act terms. Later it became a universal language for mathematics and an attempt to give a foundation for all of mathematics, and thereby to all sciences that are based on mathematics. -
Categorical Semantics of Constructive Set Theory
Categorical semantics of constructive set theory Beim Fachbereich Mathematik der Technischen Universit¨atDarmstadt eingereichte Habilitationsschrift von Benno van den Berg, PhD aus Emmen, die Niederlande 2 Contents 1 Introduction to the thesis 7 1.1 Logic and metamathematics . 7 1.2 Historical intermezzo . 8 1.3 Constructivity . 9 1.4 Constructive set theory . 11 1.5 Algebraic set theory . 15 1.6 Contents . 17 1.7 Warning concerning terminology . 18 1.8 Acknowledgements . 19 2 A unified approach to algebraic set theory 21 2.1 Introduction . 21 2.2 Constructive set theories . 24 2.3 Categories with small maps . 25 2.3.1 Axioms . 25 2.3.2 Consequences . 29 2.3.3 Strengthenings . 31 2.3.4 Relation to other settings . 32 2.4 Models of set theory . 33 2.5 Examples . 35 2.6 Predicative sheaf theory . 36 2.7 Predicative realizability . 37 3 Exact completion 41 3.1 Introduction . 41 3 4 CONTENTS 3.2 Categories with small maps . 45 3.2.1 Classes of small maps . 46 3.2.2 Classes of display maps . 51 3.3 Axioms for classes of small maps . 55 3.3.1 Representability . 55 3.3.2 Separation . 55 3.3.3 Power types . 55 3.3.4 Function types . 57 3.3.5 Inductive types . 58 3.3.6 Infinity . 60 3.3.7 Fullness . 61 3.4 Exactness and its applications . 63 3.5 Exact completion . 66 3.6 Stability properties of axioms for small maps . 73 3.6.1 Representability . 74 3.6.2 Separation . 74 3.6.3 Power types . -
Discover Linear Algebra Incomplete Preliminary Draft
Discover Linear Algebra Incomplete Preliminary Draft Date: November 28, 2017 L´aszl´oBabai in collaboration with Noah Halford All rights reserved. Approved for instructional use only. Commercial distribution prohibited. c 2016 L´aszl´oBabai. Last updated: November 10, 2016 Preface TO BE WRITTEN. Babai: Discover Linear Algebra. ii This chapter last updated August 21, 2016 c 2016 L´aszl´oBabai. Contents Notation ix I Matrix Theory 1 Introduction to Part I 2 1 (F, R) Column Vectors 3 1.1 (F) Column vector basics . 3 1.1.1 The domain of scalars . 3 1.2 (F) Subspaces and span . 6 1.3 (F) Linear independence and the First Miracle of Linear Algebra . 8 1.4 (F) Dot product . 12 1.5 (R) Dot product over R ................................. 14 1.6 (F) Additional exercises . 14 2 (F) Matrices 15 2.1 Matrix basics . 15 2.2 Matrix multiplication . 18 2.3 Arithmetic of diagonal and triangular matrices . 22 2.4 Permutation Matrices . 24 2.5 Additional exercises . 26 3 (F) Matrix Rank 28 3.1 Column and row rank . 28 iii iv CONTENTS 3.2 Elementary operations and Gaussian elimination . 29 3.3 Invariance of column and row rank, the Second Miracle of Linear Algebra . 31 3.4 Matrix rank and invertibility . 33 3.5 Codimension (optional) . 34 3.6 Additional exercises . 35 4 (F) Theory of Systems of Linear Equations I: Qualitative Theory 38 4.1 Homogeneous systems of linear equations . 38 4.2 General systems of linear equations . 40 5 (F, R) Affine and Convex Combinations (optional) 42 5.1 (F) Affine combinations . -
Constructive Set Theory
CST Book draft Peter Aczel and Michael Rathjen CST Book Draft 2 August 19, 2010 Contents 1 Introduction 7 2 Intuitionistic Logic 9 2.1 Constructivism . 9 2.2 The Brouwer-Heyting-Kolmogorov interpretation . 11 2.3 Counterexamples . 13 2.4 Natural Deductions . 14 2.5 A Hilbert-style system for intuitionistic logic . 17 2.6 Kripke semantics . 19 2.7 Exercises . 21 3 Some Axiom Systems 23 3.1 Classical Set Theory . 23 3.2 Intuitionistic Set Theory . 24 3.3 Basic Constructive Set Theory . 25 3.4 Elementary Constructive Set Theory . 26 3.5 Constructive Zermelo Fraenkel, CZF ................ 26 3.6 On notations for axiom systems. 27 3.7 Class Notation . 27 3.8 Russell's paradox . 28 4 Basic Set constructions in BCST 31 4.1 Ordered Pairs . 31 4.2 More class notation . 32 4.3 The Union-Replacement Scheme . 35 4.4 Exercises . 37 5 From Function Spaces to Powerset 41 5.1 Subset Collection and Exponentiation . 41 5.2 Appendix: Binary Refinement . 44 5.3 Exercises . 45 3 CST Book Draft 6 The Natural Numbers 47 6.1 Some approaches to the natural numbers . 47 6.1.1 Dedekind's characterization of the natural numbers . 47 6.1.2 The Zermelo and von Neumann natural numbers . 48 6.1.3 Lawv`ere'scharacterization of the natural numbers . 48 6.1.4 The Strong Infinity Axiom . 48 6.1.5 Some possible additional axioms concerning ! . 49 6.2 DP-structures and DP-models . 50 6.3 The von Neumann natural numbers in ECST . 51 6.3.1 The DP-model N! ..................... -
Matroidal Subdivisions, Dressians and Tropical Grassmannians
Matroidal subdivisions, Dressians and tropical Grassmannians vorgelegt von Diplom-Mathematiker Benjamin Frederik Schröter geboren in Frankfurt am Main Von der Fakultät II – Mathematik und Naturwissenschaften der Technischen Universität Berlin zur Erlangung des akademischen Grades Doktor der Naturwissenschaften – Dr. rer. nat. – genehmigte Dissertation Promotionsausschuss: Vorsitzender: Prof. Dr. Wilhelm Stannat Gutachter: Prof. Dr. Michael Joswig Prof. Dr. Hannah Markwig Senior Lecturer Ph.D. Alex Fink Tag der wissenschaftlichen Aussprache: 17. November 2017 Berlin 2018 Zusammenfassung In dieser Arbeit untersuchen wir verschiedene Aspekte von tropischen linearen Räumen und deren Modulräumen, den tropischen Grassmannschen und Dressschen. Tropische lineare Räume sind dual zu Matroidunterteilungen. Motiviert durch das Konzept der Splits, dem einfachsten Fall einer polytopalen Unterteilung, wird eine neue Klasse von Matroiden eingeführt, die mit Techniken der polyedrischen Geometrie untersucht werden kann. Diese Klasse ist sehr groß, da sie alle Paving-Matroide und weitere Matroide enthält. Die strukturellen Eigenschaften von Split-Matroiden können genutzt werden, um neue Ergebnisse in der tropischen Geometrie zu erzielen. Vor allem verwenden wir diese, um Strahlen der tropischen Grassmannschen zu konstruieren und die Dimension der Dressschen zu bestimmen. Dazu wird die Beziehung zwischen der Realisierbarkeit von Matroiden und der von tropischen linearen Räumen weiter entwickelt. Die Strahlen einer Dressschen entsprechen den Facetten des Sekundärpolytops eines Hypersimplexes. Eine besondere Klasse von Facetten bildet die Verallgemeinerung von Splits, die wir Multi-Splits nennen und die Herrmann ursprünglich als k-Splits bezeichnet hat. Wir geben eine explizite kombinatorische Beschreibung aller Multi-Splits eines Hypersimplexes. Diese korrespondieren mit Nested-Matroiden. Über die tropische Stiefelabbildung erhalten wir eine Beschreibung aller Multi-Splits für Produkte von Simplexen. -
1 Sets and Set Notation. Definition 1 (Naive Definition of a Set)
LINEAR ALGEBRA MATH 2700.006 SPRING 2013 (COHEN) LECTURE NOTES 1 Sets and Set Notation. Definition 1 (Naive Definition of a Set). A set is any collection of objects, called the elements of that set. We will most often name sets using capital letters, like A, B, X, Y , etc., while the elements of a set will usually be given lower-case letters, like x, y, z, v, etc. Two sets X and Y are called equal if X and Y consist of exactly the same elements. In this case we write X = Y . Example 1 (Examples of Sets). (1) Let X be the collection of all integers greater than or equal to 5 and strictly less than 10. Then X is a set, and we may write: X = f5; 6; 7; 8; 9g The above notation is an example of a set being described explicitly, i.e. just by listing out all of its elements. The set brackets {· · ·} indicate that we are talking about a set and not a number, sequence, or other mathematical object. (2) Let E be the set of all even natural numbers. We may write: E = f0; 2; 4; 6; 8; :::g This is an example of an explicity described set with infinitely many elements. The ellipsis (:::) in the above notation is used somewhat informally, but in this case its meaning, that we should \continue counting forever," is clear from the context. (3) Let Y be the collection of all real numbers greater than or equal to 5 and strictly less than 10. Recalling notation from previous math courses, we may write: Y = [5; 10) This is an example of using interval notation to describe a set. -
Mathematical Logic, an Introduction
Mathematical Logic, an Introduction by Peter Koepke Bonn, Winter 2019/20 Wann sollte die Mathematik je zu einem Anfang gelangen, wenn sie warten wollte, bis die Philosophie über unsere Grundbegrie zur Klarheit und Einmüthigkeit gekommen ist? Unsere einzige Rettung ist der formalistische Standpunkt, undenirte Begrie (wie Zahl, Punkt, Ding, Menge) an die Spitze zu stellen, um deren actuelle oder psychologische oder anschauliche Bedeutung wir uns nicht kümmern, und ebenso unbewiesene Sätze (Axiome), deren actuelle Richtigkeit uns nichts angeht. Aus diesen primitiven Begrien und Urtheilen gewinnen wir durch Denition und Deduction andere, und nur diese Ableitung ist unser Werk und Ziel. (Felix Hausdor, 12. Januar 1918) Table of contents 1 Introduction . 4 I First-order Logic and the Gödel Completeness Theorem . 4 2 The Syntax of rst-order logic: Symbols, words, and formulas . 4 2.1 Motivation: a mathematical statement . 5 2.2 Symbols . 5 2.3 Words . 6 2.4 Terms . 7 2.5 Formulas . 8 3 Semantics . 9 4 The satisfaction relation . 11 5 Logical implication and propositional connectives . 14 6 Substitution and term rules . 15 7 A sequent calculus . 20 8 Derivable sequent rules . 22 8.1 Auxiliary derived rules . 22 8.2 Introduction and elimination of ; ; ::: . 23 8.3 Formal proofs about . ._. .^. 24 9 Consistency . 25 1 2 Section 10 Term models and Henkin sets . 27 11 Constructing Henkin sets . 30 12 The completeness theorem . 34 13 The compactness theorem . 35 II Herbrand's Theorem and Automatic Theorem Proving . 38 14 Normal forms . 38 14.1 Negation normal form . 39 14.2 Conjunctive and disjunctive normal form . -
Local Constructive Set Theory and Inductive Definitions
Local Constructive Set Theory and Inductive Definitions Peter Aczel 1 Introduction Local Constructive Set Theory (LCST) is intended to be a local version of con- structive set theory (CST). Constructive Set Theory is an open-ended set theoretical setting for constructive mathematics that is not committed to any particular brand of constructive mathematics and, by avoiding any built-in choice principles, is also acceptable in topos mathematics, the mathematics that can be carried out in an arbi- trary topos with a natural numbers object. We refer the reader to [2] for any details, not explained in this paper, concerning CST and the specific CST axiom systems CZF and CZF+ ≡ CZF + REA. CST provides a global set theoretical setting in the sense that there is a single universe of all the mathematical objects that are in the range of the variables. By contrast a local set theory avoids the use of any global universe but instead is formu- lated in a many-sorted language that has various forms of sort including, for each sort α a power-sort Pα, the sort of all sets of elements of sort α. For each sort α there is a binary infix relation ∈α that takes two arguments, the first of sort α and the second of sort Pα. For each formula φ and each variable x of sort α, there is a comprehension term {x : α | φ} of sort Pα for which the following scheme holds. Comprehension: (∀y : α)[ y ∈α {x : α | φ} ↔ φ[y/x] ]. Here we use the notation φ[a/x] for the result of substituting a term a for free oc- curences of the variable x in the formula φ, relabelling bound variables in the stan- dard way to avoid variable clashes. -
Linear Algebra (VII)
Linear Algebra (VII) Yijia Chen 1. Review Basis and Dimension. We fix a vector space V. Lemma 1.1. Let A, B ⊆ V be two finite sets of vectors in V, possibly empty. If A is linearly indepen- dent and can be represented by B. Then jAj 6 jBj. Theorem 1.2. Let S ⊆ V and A, B ⊆ S be both maximally linearly independent in S. Then jAj = jBj. Definition 1.3. Let e1,..., en 2 V. Assume that – e1,..., en are linearly independent, – and every v 2 V can be represented by e1,..., en. Equivalently, fe1,..., eng is maximally linearly independent in V. Then fe1,..., eng is a basis of V. Note that n = 0 is allowed, and in that case, it is easy to see that V = f0g. By Theorem 1.2: 0 0 Lemma 1.4. If fe1,..., eng and fe1,..., emg be both bases of V with pairwise distinct ei’s and with 0 pairwise distinct ei, then n = m. Definition 1.5. Let fe1,..., eng be a basis of V with pairwise distinct ei’s. Then the dimension of V, denoted by dim(V), is n. Equivalently, if rank(V) is defined, then dim(V) := rank(V). 1 Theorem 1.6. Assume dim(V) = n and let u1,..., un 2 V. (1) If u1,..., un are linearly independent, then fu1,..., ung is a basis. (2) If every v 2 V can be represented by u1,..., un, then fu1,..., ung is a basis. Steinitz exchange lemma. Theorem 1.7. Assume that dim(V) = n and v1,..., vm 2 V with 1 6 m 6 n are linearly indepen- dent. -
Skolem's Paradox and Constructivism
CHARLES MCCARTY AND NEIL TENNANT SKOLEM’S PARADOX AND CONSTRUCTIVISM INTRODUCTION Skolem’s paradox has not been shown to arise for constructivism. Indeed, considerations that we shall advance below indicate that the main result cited to produce the paradox could be obtained only by methods not in mainstream intuitionistic practice. It strikes us as an important fact for the philosophy of mathematics. The intuitionistic conception of the mathematical universe appears, as far as we know, to be free from Skolemite stress. If one could discover reasons for believing this to be no accident, it would be an important new con- sideration, in addition to the meaning-theoretic ones advanced by Dummett (1978, ‘Concluding philosophical remarks’), that ought to be assessed when trying to reach a view on the question whether intuitionism is the correct philosophy of mathematics. We give below the detailed reasons why we believe that intuitionistic mathematics is indeed free of the Skolem paradox. They culminate in a strong independence result: even a very powerful version of intuitionis- tic set theory does not yield any of the usual forms of a countable downward Lowenheim - Skolem theorem. The proof draws on the general equivalence described in McCarty (1984) between intuitionistic mathematics and classical recursive mathematics. But first we set the stage by explaining the history of the (classical) paradox, and the philosophical reflections on the foundations of set theory that it has provoked. The recent symposium between Paul Benacerraf and Crispin Wright provides a focus for these considerations. Then we inspect the known proofs of the Lbwenheim-Skolem theorem, and reveal them all to be constructively unacceptable.