The Proper Forcing Axiom
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Set Theory, by Thomas Jech, Academic Press, New York, 1978, Xii + 621 Pp., '$53.00
BOOK REVIEWS 775 BULLETIN (New Series) OF THE AMERICAN MATHEMATICAL SOCIETY Volume 3, Number 1, July 1980 © 1980 American Mathematical Society 0002-9904/80/0000-0 319/$01.75 Set theory, by Thomas Jech, Academic Press, New York, 1978, xii + 621 pp., '$53.00. "General set theory is pretty trivial stuff really" (Halmos; see [H, p. vi]). At least, with the hindsight afforded by Cantor, Zermelo, and others, it is pretty trivial to do the following. First, write down a list of axioms about sets and membership, enunciating some "obviously true" set-theoretic principles; the most popular Hst today is called ZFC (the Zermelo-Fraenkel axioms with the axiom of Choice). Next, explain how, from ZFC, one may derive all of conventional mathematics, including the general theory of transfinite cardi nals and ordinals. This "trivial" part of set theory is well covered in standard texts, such as [E] or [H]. Jech's book is an introduction to the "nontrivial" part. Now, nontrivial set theory may be roughly divided into two general areas. The first area, classical set theory, is a direct outgrowth of Cantor's work. Cantor set down the basic properties of cardinal numbers. In particular, he showed that if K is a cardinal number, then 2", or exp(/c), is a cardinal strictly larger than K (if A is a set of size K, 2* is the cardinality of the family of all subsets of A). Now starting with a cardinal K, we may form larger cardinals exp(ic), exp2(ic) = exp(exp(fc)), exp3(ic) = exp(exp2(ic)), and in fact this may be continued through the transfinite to form expa(»c) for every ordinal number a. -
Forcing Axioms and Stationary Sets
ADVANCES IN MATHEMATICS 94, 256284 (1992) Forcing Axioms and Stationary Sets BOBAN VELICKOVI~ Department of Mathematics, University of California, Evans Hall, Berkeley, California 94720 INTRODUCTION Recall that a partial ordering 9 is called semi-proper iff for every suf- ficiently large regular cardinal 0 and every countable elementary submodel N of H,, where G9 is the canonical name for a Y-generic filter. The above q is called (9, N)-semi-generic. The Semi-Proper Forcing Axiom (SPFA) is the following statement: For every semi-proper 9 and every family 9 of Et, dense subsets of 9 there exists a filter G in 9 such that for every DE 9, GnD#@. SPFA+ states that if in addition a Y-name 3 for a stationary subset of wi is given, then a filter G can be found such that val,(S)= {c(<wi: 3p~Gp I~-EE$) is stationary. In general, if X is any class of posets, the forcing axioms XFA and XFA + are obtained by replacing “semi-proper LY” by “9 E X” in the above definitions. Sometimes we denote these axioms by FA(X) and FA+(.X). Thus, for example, FA(ccc) is the familiar Martin’s Axiom, MAN,. The notion of semi-proper, as an extension of a previous notion of proper, was defined and extensively studied by Shelah in [Shl J. These forcing notions generalize ccc and countably closed forcing and can be iterated without collapsing N, . SPFA is implicit in [Shl] as an obvious strengthening of the Proper Forcing Axiom (PFA), previously formulated and proved consistent by Baumgartner (see [Bal, Del]). -
Calibrating Determinacy Strength in Borel Hierarchies
University of California Los Angeles Calibrating Determinacy Strength in Borel Hierarchies A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Mathematics by Sherwood Julius Hachtman 2015 c Copyright by Sherwood Julius Hachtman 2015 Abstract of the Dissertation Calibrating Determinacy Strength in Borel Hierarchies by Sherwood Julius Hachtman Doctor of Philosophy in Mathematics University of California, Los Angeles, 2015 Professor Itay Neeman, Chair We study the strength of determinacy hypotheses in levels of two hierarchies of subsets of 0 0 1 Baire space: the standard Borel hierarchy hΣαiα<ω1 , and the hierarchy of sets hΣα(Π1)iα<ω1 in the Borel σ-algebra generated by coanalytic sets. 0 We begin with Σ3, the lowest level at which the strength of determinacy had not yet been characterized in terms of a natural theory. Building on work of Philip Welch [Wel11], 0 [Wel12], we show that Σ3 determinacy is equivalent to the existence of a β-model of the 1 axiom of Π2 monotone induction. 0 For the levels Σ4 and above, we prove best-possible refinements of old bounds due to Harvey Friedman [Fri71] and Donald A. Martin [Mar85, Mar] on the strength of determinacy in terms of iterations of the Power Set axiom. We introduce a novel family of reflection 0 principles, Π1-RAPα, and prove a level-by-level equivalence between determinacy for Σ1+α+3 and existence of a wellfounded model of Π1-RAPα. For α = 0, we have the following concise 0 result: Σ4 determinacy is equivalent to the existence of an ordinal θ so that Lθ satisfies \P(!) exists, and all wellfounded trees are ranked." 0 We connect our result on Σ4 determinacy to work of Noah Schweber [Sch13] on higher order reverse mathematics. -
Forcing Axioms and Projective Sets of Reals
FORCING AXIOMS AND PROJECTIVE SETS OF REALS RALF SCHINDLER Abstract. This paper is an introduction to forcing axioms and large cardinals. Specifically, we shall discuss the large cardinal strength of forcing axioms in the presence of regularity properties for projective sets of reals. The new result shown in this paper says that ZFC + the bounded proper forcing axiom (BPFA) + \every projective set of reals is Lebesgue measurable" is equiconsistent with ZFC + \there is a Σ1 reflecting cardinal above a remarkable cardinal." 1. Introduction. The current paper∗ is in the tradition of the following result. Theorem 1. ([HaSh85, Theorem B]) Equiconsistent are: (1) ZFC + there is a weakly compact cardinal, and (2) ZFC + Martin's axiom (MA) + every projective set of reals is Lebesgue measurable. This theorem links a large cardinal concept with a forcing axiom (MA) and a regularity property for the projective sets of reals. We shall be interested in considering forcing axioms which are somewhat stronger than MA. In particular, we shall produce the following new result.y Theorem 2. Equiconsistent are: (1) ZFC + there is a Σ1 reflecting cardinal above a remarkable car- dinal, and (2) ZFC + the bounded proper forcing axiom (BPFA) + every projec- tive set of reals is Lebesgue measurable. 1991 Mathematics Subject Classification. Primary 03E55, 03E15. Secondary 03E35, 03E60. Key words and phrases. set theory/forcing axioms/large cardinals/descriptive set theory. ∗The author would like to thank Ilijas Farah, Ernest Schimmerling, and Boban Velickovic for sharing with him mathematical and historical insights. yThis theorem was first presented in a talk at the 6e Atelier International de Th´eorie des Ensembles in Luminy, France, on Sept 20, 2000. -
Martin's Maximum Revisited
Martin’s maximum revisited Matteo Viale Abstract We present several results relating the general theory of the stationary tower forcing developed by Woodin with forcing axioms. In particular we show that, in combination with strong large cardinals, the forcing axiom ++ Π MM makes the 2-fragment of the theory of Hℵ2 invariant with respect to stationary set preserving forcings that preserve BMM. We argue that this is a close to optimal generalization to Hℵ2 of Woodin’s absoluteness results for L(). In due course of proving this we shall give a new proof of some of Woodin’s results. 1 Introduction In this introduction we shall take a long detour to motivate the results we want to present and to show how they stem out of Woodin’s work on Ω-logic. We tried to make this introduction comprehensible to any person acquainted with the theory of forcing as presented for example in [7]. The reader may refer to subsection 1.1 for unexplained notions. Since its discovery in the early sixties by Paul Cohen [2], forcing has played a central role in the development of modern set theory. It was soon realized its fun- arXiv:1110.1181v2 [math.LO] 9 Feb 2012 damental role to establish the undecidability in ZFC of all the classical problems of set theory, among which Cantor’s continuum problem. Moreover, up to date, forcing (or class forcing) is the unique efficient method to obtain independence results over ZFC. This method has found applications in virtually all fields of pure mathematics: in the last forty years natural problems of group theory, func- tional analysis, operator algebras, general topology, and many other subjects were shown to be undecidable by means of forcing (see [4, 13] among others). -
Arxiv:1901.02074V1 [Math.LO] 4 Jan 2019 a Xoskona Lrecrias Ih Eal Ogv Entv a Definitive a Give T to of Able Basis Be the Might Cardinals” [17]
GENERIC LARGE CARDINALS AS AXIOMS MONROE ESKEW Abstract. We argue against Foreman’s proposal to settle the continuum hy- pothesis and other classical independent questions via the adoption of generic large cardinal axioms. Shortly after proving that the set of all real numbers has a strictly larger car- dinality than the set of integers, Cantor conjectured his Continuum Hypothesis (CH): that there is no set of a size strictly in between that of the integers and the real numbers [1]. A resolution of CH was the first problem on Hilbert’s famous list presented in 1900 [19]. G¨odel made a major advance by constructing a model of the Zermelo-Frankel (ZF) axioms for set theory in which the Axiom of Choice and CH both hold, starting from a model of ZF. This showed that the axiom system ZF, if consistent on its own, could not disprove Choice, and that ZF with Choice (ZFC), a system which suffices to formalize the methods of ordinary mathematics, could not disprove CH [16]. It remained unknown at the time whether models of ZFC could be found in which CH was false, but G¨odel began to suspect that this was possible, and hence that CH could not be settled on the basis of the normal methods of mathematics. G¨odel remained hopeful, however, that new mathemati- cal axioms known as “large cardinals” might be able to give a definitive answer on CH [17]. The independence of CH from ZFC was finally solved by Cohen’s invention of the method of forcing [2]. Cohen’s method showed that ZFC could not prove CH either, and in fact could not put any kind of bound on the possible number of cardinals between the sizes of the integers and the reals. -
Martin's Maximum and Weak Square
PROCEEDINGS OF THE AMERICAN MATHEMATICAL SOCIETY Volume 00, Number 0, Pages 000{000 S 0002-9939(XX)0000-0 MARTIN'S MAXIMUM AND WEAK SQUARE JAMES CUMMINGS AND MENACHEM MAGIDOR (Communicated by Julia Knight) Abstract. We analyse the influence of the forcing axiom Martin's Maximum on the existence of square sequences, with a focus on the weak square principle λ,µ. 1. Introduction It is well known that strong forcing axioms (for example PFA, MM) and strong large cardinal axioms (strongly compact, supercompact) exert rather similar kinds of influence on the combinatorics of infinite cardinals. This is perhaps not so sur- prising when we consider the widely held belief that essentially the only way to obtain a model of PFA or MM is to collapse a supercompact cardinal to become !2. We quote a few results which bring out the similarities: 1a) (Solovay [14]) If κ is supercompact then λ fails for all λ ≥ κ. 1b) (Todorˇcevi´c[15]) If PFA holds then λ fails for all λ ≥ !2. ∗ 2a) (Shelah [11]) If κ is supercompact then λ fails for all λ such that cf(λ) < κ < λ. ∗ 2b) (Magidor, see Theorem 1.2) If MM holds then λ fails for all λ such that cf(λ) = !. 3a) (Solovay [13]) If κ is supercompact then SCH holds at all singular cardinals greater than κ. 3b) (Foreman, Magidor and Shelah [7]) If MM holds then SCH holds. 3c) (Viale [16]) If PFA holds then SCH holds. In fact both the p-ideal di- chotomy and the mapping reflection principle (which are well known con- sequences of PFA) suffice to prove SCH. -
A General Setting for the Pointwise Investigation of Determinacy
A General Setting for the Pointwise Investigation of Determinacy Yurii Khomskii? Institute of Logic, Language and Computation University of Amsterdam Plantage Muidergracht 24 1018 TV Amsterdam The Netherlands Abstract. It is well-known that if we assume a large class of sets of reals to be determined then we may conclude that all sets in this class have certain regularity properties: we say that determinacy implies regularity properties classwise. In [L¨o05]the pointwise relation between determi- nacy and certain regularity properties (namely the Marczewski-Burstin algebra of arboreal forcing notions and a corresponding weak version) was examined. An open question was how this result extends to topological forcing no- tions whose natural measurability algebra is the class of sets having the Baire property. We study the relationship between the two cases, and using a definition which adequately generalizes both the Marczewski- Burstin algebra of measurability and the Baire property, prove results similar to [L¨o05]. We also show how this can be further generalized for the purpose of comparing algebras of measurability of various forcing notions. 1 Introduction The classical theorems due to Mycielski-Swierczkowski, Banach-Mazur and Mor- ton Davis respectively state that under the Axiom of Determinacy all sets of reals are Lebesgue measurable, have the Baire property and the perfect set property (see, e.g., [Ka94, pp 373{377]). In fact, these proofs give classwise implications, i.e., if Γ is a boldface pointclass (closed under continuous preimages and inter- sections with basic open sets) such that all sets in Γ are determined, then all sets in Γ have the corresponding regularity property. -
Equivalents to the Axiom of Choice and Their Uses A
EQUIVALENTS TO THE AXIOM OF CHOICE AND THEIR USES A Thesis Presented to The Faculty of the Department of Mathematics California State University, Los Angeles In Partial Fulfillment of the Requirements for the Degree Master of Science in Mathematics By James Szufu Yang c 2015 James Szufu Yang ALL RIGHTS RESERVED ii The thesis of James Szufu Yang is approved. Mike Krebs, Ph.D. Kristin Webster, Ph.D. Michael Hoffman, Ph.D., Committee Chair Grant Fraser, Ph.D., Department Chair California State University, Los Angeles June 2015 iii ABSTRACT Equivalents to the Axiom of Choice and Their Uses By James Szufu Yang In set theory, the Axiom of Choice (AC) was formulated in 1904 by Ernst Zermelo. It is an addition to the older Zermelo-Fraenkel (ZF) set theory. We call it Zermelo-Fraenkel set theory with the Axiom of Choice and abbreviate it as ZFC. This paper starts with an introduction to the foundations of ZFC set the- ory, which includes the Zermelo-Fraenkel axioms, partially ordered sets (posets), the Cartesian product, the Axiom of Choice, and their related proofs. It then intro- duces several equivalent forms of the Axiom of Choice and proves that they are all equivalent. In the end, equivalents to the Axiom of Choice are used to prove a few fundamental theorems in set theory, linear analysis, and abstract algebra. This paper is concluded by a brief review of the work in it, followed by a few points of interest for further study in mathematics and/or set theory. iv ACKNOWLEDGMENTS Between the two department requirements to complete a master's degree in mathematics − the comprehensive exams and a thesis, I really wanted to experience doing a research and writing a serious academic paper. -
Forcing in Proof Theory∗
Forcing in proof theory¤ Jeremy Avigad November 3, 2004 Abstract Paul Cohen's method of forcing, together with Saul Kripke's related semantics for modal and intuitionistic logic, has had profound e®ects on a number of branches of mathematical logic, from set theory and model theory to constructive and categorical logic. Here, I argue that forcing also has a place in traditional Hilbert-style proof theory, where the goal is to formalize portions of ordinary mathematics in restricted axiomatic theories, and study those theories in constructive or syntactic terms. I will discuss the aspects of forcing that are useful in this respect, and some sample applications. The latter include ways of obtaining conservation re- sults for classical and intuitionistic theories, interpreting classical theories in constructive ones, and constructivizing model-theoretic arguments. 1 Introduction In 1963, Paul Cohen introduced the method of forcing to prove the indepen- dence of both the axiom of choice and the continuum hypothesis from Zermelo- Fraenkel set theory. It was not long before Saul Kripke noted a connection be- tween forcing and his semantics for modal and intuitionistic logic, which had, in turn, appeared in a series of papers between 1959 and 1965. By 1965, Scott and Solovay had rephrased Cohen's forcing construction in terms of Boolean-valued models, foreshadowing deeper algebraic connections between forcing, Kripke se- mantics, and Grothendieck's notion of a topos of sheaves. In particular, Lawvere and Tierney were soon able to recast Cohen's original independence proofs as sheaf constructions.1 It is safe to say that these developments have had a profound impact on most branches of mathematical logic. -
UC Irvine UC Irvine Electronic Theses and Dissertations
UC Irvine UC Irvine Electronic Theses and Dissertations Title Axiom Selection by Maximization: V = Ultimate L vs Forcing Axioms Permalink https://escholarship.org/uc/item/9875g511 Author Schatz, Jeffrey Robert Publication Date 2019 Peer reviewed|Thesis/dissertation eScholarship.org Powered by the California Digital Library University of California UNIVERSITY OF CALIFORNIA, IRVINE Axiom Selection by Maximization: V = Ultimate L vs Forcing Axioms DISSERTATION submitted in partial satisfaction of the requirements for the degree of DOCTOR OF PHILOSOPHY in Philosophy by Jeffrey Robert Schatz Dissertation Committee: Distinguished Professor Penelope Maddy, Chair Professor Toby Meadows Dean’s Professor Kai Wehmeier Professor Jeremy Heis 2019 All materials c 2019 Jeffrey Robert Schatz DEDICATION To Mike and Lori Schatz for always encouraging me to pursue my goals AND In memory of Jackie, a true and honest friend. ii TABLE OF CONTENTS Page ACKNOWLEDGMENTS iv CURRICULUM VITAE vi ABSTRACT OF THE DISSERTATION vii CHAPTER 1: Two Contemporary Candidates for A Strong Theory of Sets 1 1 The Axiomatization of Set Theory and The Question of Axiom Selection 2 1.1 The Inner Model Program 14 1.2 The Forcing Axiom Program 27 1.3 How to Settle This Dispute? 36 1.4 CHAPTER 2: Axiom Selection and the Maxim of ‘Maximize’ 38 2 ‘Maximize’ as a Methodological Maxim 39 2.1 Two Notions of Maximize 43 2.2 Re-characterizing M-Max for Extensions of ZFC 50 2.3 CHAPTER 3: Applying ‘Maximize’ to Contemporary Axiom Candidates 53 3 Towards a Theory for Ultimate L 54 3.1 S-Max: -
Tuple Routing Strategies for Distributed Eddies
Tuple Routing Strategies for Distributed Eddies Feng Tian David J. DeWitt Department of Computer Sciences University of Wisconsin, Madison Madison, WI, 53706 {ftian, dewitt}@cs.wisc.edu Abstract data stream management systems has begun to receive the attention of the database community. Many applications that consist of streams of data Many of the fundamental assumptions that are the are inherently distributed. Since input stream basis of standard database systems no longer hold for data rates and other system parameters such as the stream management systems [8]. A typical stream query is amount of available computing resources can long running -- it listens on several continuous streams fluctuate significantly, a stream query plan must and produces a continuous stream as its result. The notion be able to adapt to these changes. Routing tuples of running time, which is used as an optimization goal by between operators of a distributed stream query a classic database optimizer, cannot be directly applied to plan is used in several data stream management a stream management system. A data stream management systems as an adaptive query optimization system must use other performance metrics. In addition, technique. The routing policy used can have a since the input stream rates and the available computing significant impact on system performance. In this resources will usually fluctuate over time, an execution paper, we use a queuing network to model a plan that works well at query installation time might be distributed stream query plan and define very inefficient just a short time later. Furthermore, the performance metrics for response time and “optimize-then-execute” paradigm of traditional database system throughput.