A note on the representation of general recursive functions and the μ quantifier

1959 ◽  
Vol 55 (2) ◽  
pp. 145-148
Author(s):  
Alan Rose
Keyword(s):  
Natural Number ◽  
Recursive Function ◽  
Natural Numbers ◽  
General Recursive Function ◽  
Recursive Functions ◽  
Image Position ◽  
Primitive Recursive

It has been shown that every general recursive function is definable by application of the five schemata for primitive recursive functions together with the schemasubject to the condition that, for each n–tuple of natural numbers x1,…, xn there exists a natural number xn+1 such that

Arithmetical representation of recursively enumerable sets

1956 ◽  
Vol 21 (2) ◽  
pp. 162-186 ◽  
Author(s):  
Raphael M. Robinson
Keyword(s):  
Recursive Function ◽  
Natural Numbers ◽  
General Recursive Function ◽  
Recursively Enumerable Set ◽  
Integer Coefficients ◽  
Primitive Recursive Function ◽  
Recursively Enumerable ◽  
Image Position ◽  
The Right ◽  
Primitive Recursive

A set S of natural numbers is called recursively enumerable if there is a general recursive function F(x, y) such thatIn other words, S is the projection of a two-dimensional general recursive set. Actually, it is no restriction on S to assume that F(x, y) is primitive recursive. If S is not empty, it is the range of the primitive recursive functionwhere a is a fixed element of S. Using pairing functions, we see that any non-empty recursively enumerable set is also the range of a primitive recursive function of one variable.We use throughout the logical symbols ⋀ (and), ⋁ (or), → (if…then…), ↔ (if and only if), ∧ (for every), and ∨(there exists); negation does not occur explicitly. The variables range over the natural numbers, except as otherwise noted.Martin Davis has shown that every recursively enumerable set S of natural numbers can be represented in the formwhere P(y, b, w, x1 …, xλ) is a polynomial with integer coefficients. (Notice that this would not be correct if we replaced ≤ by <, since the right side of the equivalence would always be satisfied by b = 0.) Conversely, every set S represented by a formula of the above form is recursively enumerable. A basic unsolved problem is whether S can be defined using only existential quantifiers.

A note on nominalism and recursive functions

1949 ◽  
Vol 14 (1) ◽  
pp. 27-31 ◽  
Author(s):  
R. M. Martin
Keyword(s):  
General Theory ◽  
Philosophy Of Science ◽  
Recursive Function ◽  
Homogeneous System ◽  
Formal Logic ◽  
Abstract Objects ◽  
Natural Numbers ◽  
General Recursive Function ◽  
Recursive Functions ◽  
Definition Of

The purpose of this note is (i) to point out an important similarity between the nominalistic system discussed by Quine in his recent paper On universals and the system of logic (the system н) developed by the author in A homogeneous system for formal logic, (ii) to offer certain corrections to the latter, and (iii) to show that that system (н) is adequate for the general theory of ancestrale and for the definition of any general recursive function of natural numbers.Nominalism as a thesis in the philosophy of science, according to Quine, is the view that it is possible to construct a language adequate for the purposes of science, which in no wise admits classes, properties, relations, or other abstract objects as values for variables.

The recursive irrationality of π

1954 ◽  
Vol 19 (4) ◽  
pp. 267-274 ◽  
Author(s):  
R. L. Goodstein
Keyword(s):  
Real Number ◽  
Recursive Function ◽  
Present Note ◽  
Rational Numbers ◽  
Negative Integer ◽  
Exponential Series ◽  
General Recursive Function ◽  
Recursive Sequence ◽  
Image Position ◽  
Primitive Recursive

A primitive-recursive sequence of rational numbers sn is said to be primitive-recursively irrational, if there are primitive recursive functions n(k), i(p, q) > 0 and N(p, q) such that:1. (k)(n ≥ n(k) → ∣sn – sn(k)∣ < 2−k).2. (p)(q)(q > 0 & n ≥ N(p, q) → ∣sn ± p/q∣ > 1/i(p, q)).The object of the present note is to establish the primitive-recursive irrationality of a sequence which converges to π. In a previous paper we proved the primitive-recursive irrationality of the exponential series Σxn/n!, for all rational values of x, and showed that a primitive-(general-) recursively irrational sequence sn is strongly primitive-(general-)recursive convergent in any scale, where a recursive sequence sn is said to be strongly primitive-(general-)recursive convergent in the scale r (r ≥ 2), if there is a non-decreasing primitive-(general-) recursive function r(k) such that,where [x] is the greatest integer contained in x, i.e. [x] = i if i ≤ x < i + 1, [x] = —i if i ≤ —x < i+1, where i is a non-negative integer.A rational recursive sequence sn is said to be recursive convergent, if there is a recursive function n(k) such that.If a sequence sn is strongly recursive convergent in a scale r, then it is recursive convergent and its limit is the recursive real number where, for any k ≥ 0,.

Note on a conjecture of Skolem

1946 ◽  
Vol 11 (3) ◽  
pp. 73-74 ◽  
Author(s):  
Emil L. Post
Keyword(s):  
Recursive Function ◽  
Recursive Relation ◽  
Natural Numbers ◽  
Excellent Review ◽  
Recursive Functions ◽  
Diagonal Argument ◽  
Primitive Recursive ◽  
Recursive Relations

In his excellent review of four notes of Skolem on recursive functions of natural numbers Bernays states: “The question whether every relation y = f(x1,…, xn) with a recursive function ƒ is primitive recursive remains undecided.” Actually, the question is easily answered in the negative by a form of the familiar diagonal argument.We start with the ternary recursive relation R, referred to in the review, such that R(x, y, 0), R(x, y, 1), … is an enumeration of all binary primitive recursive relations.

A Hierarchy on the Class of Primitive Recursive Ordinal Functions

1976 ◽  
Vol 28 (6) ◽  
pp. 1205-1209
Author(s):  
Stanley H. Stahl
Keyword(s):  
Natural Numbers ◽  
Recursive Functions ◽  
Set Functions ◽  
Primitive Recursive ◽  
Class Of Functions ◽  
Recursive Set

The class of primitive recursive ordinal functions (PR) has been studied recently by numerous recursion theorists and set theorists (see, for example, Platek [3] and Jensen-Karp [2]). These investigations have been part of an inquiry concerning a larger class of functions; in Platek's case, the class of ordinal recursive functions and in the case of Jensen and Karp, the class of primitive recursive set functions. In [4] I began to study PR in depth and this paper is a report on an attractive analogy between PR and its progenitor, the class of primitive recursive functions on the natural numbers (Prim. Rec).

Recursive functions in basic logic

1956 ◽  
Vol 21 (4) ◽  
pp. 337-346 ◽  
Author(s):  
Frederic B. Fitch
Keyword(s):  
Basic Logic ◽  
Recursive Functions ◽  
Numerical Equality ◽  
Partial Recursive Functions ◽  
Image Position ◽  
Primitive Recursive ◽  
Double Arrow

1.1 The system K* of basic logic, as presented in a previous paper, will be shown to be formalizable in an alternative way according to which the rule [E],is replaced by the rule [F],1.2. General recursive functions will be shown to be definable in K* in a way that retains functional notation, so that the equation,will be formalized in K* by the formula,where ‘f’, ‘p1’, … ‘pn’ respectively denote φ, x1, …, xn, and where ‘≐’ plays the role of numerical equality. Partial recursive functions may be handled in a similar way. The rule [E] is not required for dealing with primitive recursive functions by this method.1.3. An operator ‘G’ will be defined such that ‘[Ga ≐ p]’ is a theorem of K* if and only if ‘p’ denotes the Gödel number of ‘a’.1.4. In reformulating K* we assume ‘o0’, ‘o1,’ ‘o2’, …, have been so chosen that we can determine effectively whether or not a given U-expression is the mth member of the above series. The revised rules for K* are then as follows. (Double-arrow forms of these rules are derivable, except in the case of rule [V].)

Repercussions of a Problem of Erdős and Ulam on Density Ideals

1990 ◽  
Vol 42 (5) ◽  
pp. 902-914 ◽  
Author(s):  
Winfried Just
Keyword(s):  
Boolean Algebra ◽  
Natural Number ◽  
Natural Numbers ◽  
Logarithmic Density ◽  
Density Zero ◽  
Image Position ◽  
The Ideal

By P(ω) we denote the Boolean algebra of all subsets of the set ω of natural numbers. We identify each natural number with the set of its predecessors and define: the ideal of sets of density zero, and the ideal of sets of logarithmic density zero.

Frequency computations and the cardinality theorem

1992 ◽  
Vol 57 (2) ◽  
pp. 682-687 ◽  
Author(s):  
Valentina Harizanov ◽  
Martin Kummer ◽  
Jim Owings
Keyword(s):  
Characteristic Function ◽  
Recursive Function ◽  
Natural Numbers ◽  
New Techniques ◽  
Semirecursive Set ◽  
Image Position ◽  
Special Case ◽  
Full Proof

In 1960 G. F. Rose [R] made the following definition: A function f: ω → ω is (m, n)-computable, where 1 ≤ m ≤ n, iff there exists a recursive function R: ωn → ωn such that, for all n-tuples (x1,…, xn) of distinct natural numbers,J. Myhill (see [McN, p. 393]) asked if f had to be recursive if m was close to n; B. A. Trakhtenbrot [T] responded by showing in 1963 that f is recursive whenever 2m > n. This result is optimal, because, for example, the characteristic function of any semirecursive set is (1,2)-computable. Trakhtenbrot's work was extended by E. B. Kinber [Ki1], using similar techniques. In 1986 R. Beigel [B] made a powerful conjecture, much more general than the above results. Partial verification, falling short of a full proof, appeared in [O]. Using new techniques, M. Kummer has recently established the conjecture, which will henceforth be referred to as the cardinality theorem (CT). It is the goal of this paper to show the connections between these various theorems, to review the methods used by Trakhtenbrot, and to use them to prove a special case of CT strong enough to imply Kinber's theorem (see §3). We thus have a hierarchy of results, with CT at the top. We will also include a discussion of Kummer's methods, but not a proof of CT.

Primitive recursive ordinal functions with added constants

1977 ◽  
Vol 42 (1) ◽  
pp. 77-82
Author(s):  
Stanley H. Stahl
Keyword(s):  
Constant Function ◽  
Natural Numbers ◽  
Recursive Functions ◽  
Primitive Recursive

One of the basic differences between the primitive recursive functions on the natural numbers and the primitive recursive ordinal functions (PR) is the nearly complete absence of constant functions in PR. Since ω is closed under all of the functions in PR, if α is any infinite ordinal, then λξ·α is not in PR. It is easily seen, however, that if one adds to the initial functions of PR the constant function λξ·ω, then all of the ordinals up to ω#, the next largest PR-closed ordinal, have their constant functions in this class. Since, however, such collections of functions are always countable, it is also the case that if one adds to the initial functions of PR the function λξ. α for uncountable α, then there are ordinals β < α whose constant functions are not in this collection. Because of this, the following objects are of interest:Definition. For all α,(i)PR(α) is the collection of functions obtained by adding to the initial primitive recursive ordinal functions, the function λξ· α;(ii) PRsp(α), the primitive recursive spectrum of α, is the set {β < α ∣ λξβ ∈ PR(α);(iii) Λ (α)= μρ(ρ∉ PRsp(α)).

Note on the representation of integers as sums of certain powers

1969 ◽  
Vol 65 (2) ◽  
pp. 445-446 ◽  
Author(s):  
K. Thanigasalam
Keyword(s):  
Asymptotic Formula ◽  
Natural Number ◽  
Natural Numbers ◽  
Waring’S Problem ◽  
Waring's Problem ◽  
Representation Of Integers ◽  
Image Position ◽  
Large Natural Number

In the paper entitled ‘Asymptotic formula in a generalized Waring's problem’, I established an asymptotic formula for the number of representations of a large natural number N in the formwhere x1, x2, …, x7 and k are natural numbers with k ≥ 4 (see (2) Theorem 2).

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