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Who gave you the Cauchy–Weierstrass tale? The dual history of rigorous calculus
 Foundations of Science
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Randomizing a Model
"... A randomization of a first order structure M is a new structure with certain closure properties whose universe is a set K of "random elements" of M. Randomizations assign probabilities to sentences of the language of M with new constants from K. Our main theorem shows that all randomizati ..."
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A randomization of a first order structure M is a new structure with certain closure properties whose universe is a set K of "random elements" of M. Randomizations assign probabilities to sentences of the language of M with new constants from K. Our main theorem shows that all randomizations of M are models of the same first order theory T , which has a nice set of axioms and admits elimination of quantifiers. Moreover, the class of substructures of models of T is characterized by a natural set V of universal axioms of T , so that T is the model completion of V . 1 Introduction A common theme in mathematics is to start with a first order structure M, and introduce a new structure K which has a set K of "random elements" of M as a universe and which assigns probabilities to sentences of the language of M with new constants from K. There are several ways to do this; three wellknown examples will be given in this introduction, and many others will be given in Section 4. The aim of thi...
Tennenbaum’s Theorem for Models of Arithmetic
, 2006
"... This paper discusses Tennenbaum’s Theorem in its original context of models of arithmetic, which states that there are no recursive nonstandard models of Peano Arithmetic. We focus on three separate areas: the historical background to the theorem; an understanding of the theorem and its relationship ..."
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This paper discusses Tennenbaum’s Theorem in its original context of models of arithmetic, which states that there are no recursive nonstandard models of Peano Arithmetic. We focus on three separate areas: the historical background to the theorem; an understanding of the theorem and its relationship with the Gödel–Rosser Theorem; and extensions of Tennenbaum’s theorem to diophantine problems in models of arthmetic, especially problems concerning which diophantine equations have roots in some model of a given theory of arithmetic.
Generating Counterexamples for Structural Inductions by Exploiting Nonstandard Models
"... Abstract. Induction proofs often fail because the stated theorem is noninductive, in which case the user must strengthen the theorem or prove auxiliary properties before performing the induction step. (Counter)model finders are useful for detecting nontheorems, but they will not find any counterexa ..."
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Abstract. Induction proofs often fail because the stated theorem is noninductive, in which case the user must strengthen the theorem or prove auxiliary properties before performing the induction step. (Counter)model finders are useful for detecting nontheorems, but they will not find any counterexamples for noninductive theorems. We explain how to apply a wellknown concept from firstorder logic, nonstandard models, to the detection of noninductive invariants. Our work was done in the context of the proof assistant Isabelle/HOL and the counterexample generator Nitpick. 1
Realizability with a Local Operator of A.M. Pitts
, 2013
"... We study a notion of realizability with a local operator J which was first considered by A.M. Pitts in his thesis [7]. Using the SuslinKleene theorem, we show that the representable functions for this realizability are exactly the hyperarithmetical ( ∆ 1 1) functions. We show that there is a realiz ..."
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We study a notion of realizability with a local operator J which was first considered by A.M. Pitts in his thesis [7]. Using the SuslinKleene theorem, we show that the representable functions for this realizability are exactly the hyperarithmetical ( ∆ 1 1) functions. We show that there is a realizability interpretation of nonstandard arithmetic, which, despite its classical character, lives in a very nonclassical universe, where the Uniformity Principle holds and König’s Lemma fails. We conjecture that the local operator gives a useful indexing of the hyperarithmetical functions.
Arithmetic and the Incompleteness Theorems
, 2000
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SET THEORY FROM CANTOR TO COHEN
"... Set theory is an autonomous and sophisticated field of mathematics, enormously successful not only at its continuing development of its historical heritage but also at analyzing mathematical propositions and gauging their consistency strength. But set theory is also distinguished by having begun int ..."
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Set theory is an autonomous and sophisticated field of mathematics, enormously successful not only at its continuing development of its historical heritage but also at analyzing mathematical propositions and gauging their consistency strength. But set theory is also distinguished by having begun intertwined with pronounced metaphysical attitudes, and these have even been regarded as crucial by some of its great developers. This has encouraged the exaggeration of crises in foundations and of metaphysical doctrines in general. However, set theory has proceeded in the opposite direction, from a web of intensions to a theory of extension par excellence, and like other fields of mathematics its vitality and progress have depended on a steadily growing core of mathematical proofs and methods, problems and results. There is also the stronger contention that from the beginning set theory actually developed through a progression of mathematical moves, whatever and sometimes in spite of what has been claimed on its behalf. What follows is an account of the development of set theory from its beginnings through the creation of forcing based on these contentions, with an avowedly Whiggish emphasis on the heritage that has been retained and developed by the current theory. The