Numbers

2019 ◽  
pp. 139-170
Author(s):  
Christopher Peacocke

This chapter develops a metaphysics-first view of natural numbers and real numbers. The account gives a philosophical priority to applications: to the application of natural numbers as numbering property-instances, and to the application of real numbers as ratios of extensive magnitudes. Each natural number is individuated by the condition for it to be the number of a property. The account is contrasted with the neo-Fregean approach to natural numbers advocated by Wright; but it does have a natural marriage with the postulationist approach of Fine. This metaphysics of numbers can then be deployed in combination with the principle that, for these ontologies, Individuation Precedes Representation. To be capable of representing numbers of these kinds is to have tacit knowledge of the principles that individuate them. The resulting account has both differences from and affinities with the views of Carnap.

Kybernetes ◽  
2008 ◽  
Vol 37 (3/4) ◽  
pp. 453-457 ◽  
Author(s):  
Wujia Zhu ◽  
Yi Lin ◽  
Guoping Du ◽  
Ningsheng Gong

PurposeThe purpose is to show that all uncountable infinite sets are self‐contradictory non‐sets.Design/methodology/approachA conceptual approach is taken in the paper.FindingsGiven the fact that the set N={x|n(x)} of all natural numbers, where n(x)=df “x is a natural number” is a self‐contradicting non‐set in this paper, the authors prove that in the framework of modern axiomatic set theory ZFC, various uncountable infinite sets are either non‐existent or self‐contradicting non‐sets. Therefore, it can be astonishingly concluded that in both the naive set theory or the modern axiomatic set theory, if any of the actual infinite sets exists, it must be a self‐contradicting non‐set.Originality/valueThe first time in history, it is shown that such convenient notion as the set of all real numbers needs to be reconsidered.


1998 ◽  
Vol 29 (1) ◽  
pp. 41-45
Author(s):  
BORIS LAVRIC

We consider sequences  in a Dedekind $\sigma$-complete Riese space, satisfying a recursive relation \[ x_{n+p}\ge \sum_{j=1}^p \alpha_{n,j} x_{n+p-j} \qquad \text{for } n=1, 2, \cdots\] where $p$ is a given natural number and $\alpha_{n,j}$ are nonnegative real numbers satisfying $\sum_{j=1}^p\alpha_{n,j}=1$. We obtain a sufficient condition on coefficients $\alpha_{n,j}$ for which order boundedness of such a sequence $(x_n)_{n=1}^\infty$ implies its order convergence. In a particular case when $\alpha_{n,j}=\alpha_{j}$ for all $n$ and $j$, it is shown that every order bounded sequence satisfying the above recursive relation order converges if and only if natural numbers $j \le p$ for which $\alpha_{j}>0$, are relative prime.


Author(s):  
Juan Pablo Ramirez

We provide a construction of natural numbers that is unique with respect to other constructions, and use this construction in the domain of algebra and finite functions to find several results in finite group theory. First, we give a linear order to the set of all finite functions. This gives a linear order in the subset of all finite permutations. To do this, we assign a unique natural number, $N_f$, to every finite function $f$. The sub order on permutations is well defined with respect to cardinality; if $\eta_m,\eta_n$ are permutations on $m<n$ objects, then $N_{\eta_m}<N_{\eta_n}$. This representation also has the characteristic $N_{\textbf{1}_n}<N_{\eta}<N_{\textbf{id}_n}$ where $\textbf{1}_n$ is the one-cycle permutation of $n$ objects, $\textbf{id}_n$ is the identity permutation of $n$ objects, and $\eta$ is any permutation of $n$ objects. This representation provides a good definition of equivalent functions, and equivalent objects on functions. We are able to do this for both concrete functions, and abstract functions. We use this in the main section, on group theory, to number the set of all finite groups. We are able to well represent every finite group as a natural number; two groups are represented by the same natural number if and only if they are in the same isomorphism class. In fact, we are able to give a linear order to the set of finite groups. Specifically, we give a canonical bijective function $\textbf{G}_{Fin}\rightarrow\mathbb N$. This representation, $N_G$, of $G$, is also well behaved with respect to cardinality. Additionally, the cyclic group $\mathbb Z_n$ has smaller representation than any group of $n$ objects, and the group with largest representation is the abelian group $\mathbb Z_{p_1}^{n_1}\oplus\mathbb Z_{p_2}^{n_2}\oplus\cdots\oplus\mathbb Z_{p_k}^{n_k}$, where $n=p_1^{n_1}p_2^{n_2}\cdots p_{k}^{n_k}$ is the prime factorization of $n$. This representation of a finite group as a natural number also provides a linear order to the elements of the group, arranging its Cayley table in a canonical block form. The last section is an introductory description of real numbers as infinite sets of natural numbers. Real functions are represented as sets of real numbers, and sequences of real functions $f_1,f_2,\ldots$ are well represented by sets of real numbers, as well. In the last section we well assign mathematical objects to tree structures and conclude with some brief comments on type theory and future work. In general we are able to represent and manipulate mathematical objects with the smallest possible type, and minimum complexity.


Author(s):  
Juan Pablo Ramirez

We provide a construction of natural numbers that is unique with respect to other constructions, and use this construction in the domain of algebra and finite functions to find several results in finite group theory. First, we give a linear order to the set of all finite functions. This gives a linear order in the subset of all finite permutations. To do this, we assign a unique natural number, $N_f$, to every finite function $f$. The sub order on permutations is well defined with respect to cardinality; if $\eta_m,\eta_n$ are permutations on $m<n$ objects, then $N_{\eta_m}<N_{\eta_n}$. This representation also has the characteristic $N_{\textbf{1}_n}<N_{\eta}<N_{\textbf{id}_n}$ where $\textbf{1}_n$ is the one-cycle permutation of $n$ objects, $\textbf{id}_n$ is the identity permutation of $n$ objects, and $\eta$ is any permutation of $n$ objects. This representation provides a good definition of equivalent functions, and equivalent objects on functions. We are able to do this for both concrete functions, and abstract functions. We use this in the main section, on group theory, to number the set of all finite groups. We are able to well represent every finite group as a natural number; two groups are represented by the same natural number if and only if they are in the same isomorphism class. In fact, we are able to give a linear order to the set of finite groups. Specifically, we give a canonical bijective function $\textbf{G}_{Fin}\rightarrow\mathbb N$. This representation, $N_G$, of $G$, is also well behaved with respect to cardinality. Additionally, the cyclic group $\mathbb Z_n$ has smaller representation than any group of $n$ objects, and the group with largest representation is the abelian group $\mathbb Z_{p_1}^{n_1}\oplus\mathbb Z_{p_2}^{n_2}\oplus\cdots\oplus\mathbb Z_{p_k}^{n_k}$, where $n=p_1^{n_1}p_2^{n_2}\cdots p_{k}^{n_k}$ is the prime factorization of $n$. This representation of a finite group as a natural number also provides a linear order to the elements of the group, arranging its Cayley table in a canonical block form. The last section is an introductory description of real numbers as infinite sets of natural numbers. Real functions are represented as sets of real numbers, and sequences of real functions $f_1,f_2,\ldots$ are well represented by sets of real numbers, as well. In the last section we well assign mathematical objects to tree structures and conclude with some brief comments on type theory and future work. In general we are able to represent and manipulate mathematical objects with the smallest possible type, and minimum complexity.


Author(s):  
Øystein Linnebo

How are the natural numbers individuated? That is, what is our most basic way of singling out a natural number for reference in language or in thought? According to Frege and many of his followers, the natural numbers are cardinal numbers, individuated by the cardinalities of the collections that they number. Another answer regards the natural numbers as ordinal numbers, individuated by their positions in the natural number sequence. Some reasons to favor the second answer are presented. This answer is therefore developed in more detail, involving a form of abstraction on numerals. Based on this answer, a justification for the axioms of Dedekind–Peano arithmetic is developed.


2012 ◽  
Vol 22 (4-5) ◽  
pp. 614-704 ◽  
Author(s):  
NICOLAS POUILLARD ◽  
FRANÇOIS POTTIER

AbstractAtoms and de Bruijn indices are two well-known representation techniques for data structures that involve names and binders. However, using either technique, it is all too easy to make a programming error that causes one name to be used where another was intended. We propose an abstract interface to names and binders that rules out many of these errors. This interface is implemented as a library in Agda. It allows defining and manipulating term representations in nominal style and in de Bruijn style. The programmer is not forced to choose between these styles: on the contrary, the library allows using both styles in the same program, if desired. Whereas indexing the types of names and terms with a natural number is a well-known technique to better control the use of de Bruijn indices, we index types with worlds. Worlds are at the same time more precise and more abstract than natural numbers. Via logical relations and parametricity, we are able to demonstrate in what sense our library is safe, and to obtain theorems for free about world-polymorphic functions. For instance, we prove that a world-polymorphic term transformation function must commute with any renaming of the free variables. The proof is entirely carried out in Agda.


Author(s):  
Susan D'Agostino

“Proceed with care, because some infinities are larger than others” explains in detail why the infinite set of real numbers—all of the numbers on the number line—represents a far larger infinity than the infinite set of natural numbers—the counting numbers. Readers learn to distinguish between countable infinity and uncountable infinity by way of a method known as a “one-to-one correspondence.” Mathematics students and enthusiasts are encouraged to proceed with care in both mathematics and life, lest they confuse countable infinity with uncountable infinity, large with unfathomably large, or order with disorder. At the chapter’s end, readers may check their understanding by working on a problem. A solution is provided.


10.14311/1821 ◽  
2013 ◽  
Vol 53 (4) ◽  
Author(s):  
L'ubomíra Balková ◽  
Aranka Hrušková

In this paper, we will first summarize known results concerning continued fractions. Then we will limit our consideration to continued fractions of quadratic numbers. The second author describes periods and sometimes the precise form of continued fractions of ?N, where N is a natural number. In cases where we have been able to find such results in the literature, we recall the original authors, however many results seem to be new.


2013 ◽  
Vol 13 (4-5) ◽  
pp. 847-861 ◽  
Author(s):  
PAUL TARAU

AbstractWe describe a compact serialization algorithm mapping Prolog terms to natural numbers of bit-sizes proportional to the memory representation of the terms. The algorithm is a ‘no bit lost’ bijection, as it associates to each Prolog term a unique natural number and each natural number corresponds to a unique syntactically well-formed term.To avoid an exponential explosion resulting from bijections mapping term trees to natural numbers, we separate the symbol content and the syntactic skeleton of a term that we serialize compactly using a ranking algorithm for Catalan families.A novel algorithm for the generalized Cantor bijection between ${\mathbb{N}$ and ${\mathbb{N}$k is used in the process of assigning polynomially bounded Gödel numberings to various data objects involved in the translation.


2011 ◽  
Vol 07 (03) ◽  
pp. 579-591 ◽  
Author(s):  
PAUL POLLACK

For each natural number N, let R(N) denote the number of representations of N as a sum of two primes. Hardy and Littlewood proposed a plausible asymptotic formula for R(2N) and showed, under the assumption of the Riemann Hypothesis for Dirichlet L-functions, that the formula holds "on average" in a certain sense. From this they deduced (under ERH) that all but Oϵ(x1/2+ϵ) of the even natural numbers in [1, x] can be written as a sum of two primes. We generalize their results to the setting of polynomials over a finite field. Owing to Weil's Riemann Hypothesis, our results are unconditional.


Sign in / Sign up

Export Citation Format

Share Document