A NEW FORMALIZATION OF FEFERMAN’S SYSTEM OF FUNCTIONS AND CLASSES AND ITS RELATION TO FREGE STRUCTURE

1995 ◽  
Vol 06 (03) ◽  
pp. 187-202 ◽  
Author(s):  
SUSUMU HAYASHI ◽  
SATOSHI KOBAYASHI
Keyword(s):  
Finite Number ◽  
Order Theory ◽  
Point Of View ◽  
The Other ◽  
Technical Result ◽  
Technical Point ◽  
First Order ◽  
First Order Theory

A new axiomatization of Feferman’s systems of functions and classes1,2 is given. The new axiomatization has a finite number of class constructors resembling the proposition constructors of Frege structure by Aczel.3 Aczel wrote “It appears that from the technical point of view the two approaches (Feferman’s system and Frege structure) run parallel to each other in the sense that any technical result for one approach can be reconstructed for the other”.3 By the aid of the new axiomatization, Aczel’s observation becomes so evident. It is now straightforward to give a mutual interpretation between our formulation and a first order theory of Frege structure, which improve results by Beeson in Ref. 4.

On models of the elementary theory of (Z, +, 1)

1990 ◽  
Vol 55 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Mark Nadel ◽  
Jonathan Stavi
Keyword(s):  
Stability Theory ◽  
Elementary Theory ◽  
Additive Group ◽  
Order Theory ◽  
Point Of View ◽  
Real Numbers ◽  
First Order ◽  
First Order Theory ◽  
Distinguished Element ◽  
Unbounded Subset

Let T1 be the complete first-order theory of the additive group of the integers with 1 as distinguished element (in symbols, T1 = Th(Z, +, 1)). In this paper we prove that all models of T1 are ℵ0-homogeneous (§2), classify them (and lists of elements in them) up to isomorphism or L∞κ-equivalence (§§3 and 4) and show that they may be as complex as arbitrary sets of real numbers from the point of view of admissible set theory (§5). The results of §§2 and 5 together show that while the Scott heights of all models of T1 are ≤ ω (by ℵ0-homogeneity) their HYP-heights form an unbounded subset of the cardinal .In addition to providing this unusual example of the relation between Scott heights and HYP-heights, the theory T1 has served (using the homogeneity results of §2) as an example for certain combinations of properties that people had looked for in stability theory (see end of §4). In §6 it is shown that not all models of T = Th(Z, +) are ℵ0-homogeneous, so that the availability of the constant for 1 is essential for the result of §2.The two main results of this paper (2.2 and essentially Theorem 5.3) were obtained in the summer of 1979. Later we learnt from Victor Harnik and Julia Knight that T1 is of some interest for stability theory, and were encouraged to write up our proofs.During 1982/3 we improved the proofs and added some results.

Decidability and undecidability of theories with a predicate for the primes

1993 ◽  
Vol 58 (2) ◽  
pp. 672-687 ◽  
Author(s):  
P. T. Bateman ◽  
C. G. Jockusch ◽  
A. R. Woods
Keyword(s):  
General Result ◽  
Order Theory ◽  
Second Order ◽  
The Other ◽  
Linear Case ◽  
Natural Numbers ◽  
Successor Function ◽  
First Order ◽  
First Order Theory

AbstractIt is shown, assuming the linear case of Schinzel's Hypothesis, that the first-order theory of the structure 〈ω; +, P〉, where P is the set of primes, is undecidable and, in fact, that multiplication of natural numbers is first-order definable in this structure. In the other direction, it is shown, from the same hypothesis, that the monadic second-order theory of 〈ω S, P〉 is decidable, where S is the successor function. The latter result is proved using a general result of A. L. Semënov on decidability of monadic theories, and a proof of Semënov's result is presented.

Characteristically simple ℵ0-categorical groups

1984 ◽  
Vol 49 (3) ◽  
pp. 900-907
Author(s):  
Robert H. Gilman
Keyword(s):  
Automorphism Group ◽  
Finite Number ◽  
Simple Group ◽  
Countable Group ◽  
Order Theory ◽  
Characteristic Subgroup ◽  
First Order ◽  
First Order Theory ◽  
Direct Limits ◽  
Categorical Groups

A countable group is ℵ0-categorical if it is characterized up to isomorphism among all countable groups by its first order theory. We investigate countable ℵ0-categorical groups which are characteristically simple and have proper subgroups of finite index. We determine such groups up to isomorphism (Corollary 4 to Proposition 3), and we show that their theories are finitely axiomatizable (Proposition 2).Let K be a finite nonabelian simple group. In §3 we construct from K two denumberable groups, K* and K#, and use them to classify countable direct limits of finite Cartesian powers of K (Proposition 1). The results of §3 are used in §4 to show that K* and K# are ℵ0-categorical and to find axioms for their theories. By Corollary 2 to Proposition 2, K* and K# are counterexamples to the conjecture of U. Feigner [3, p. 309] that ℵ0-categorical groups are FC-solvable. Also in §4 the results mentioned in the first paragraph are proved. §2 is devoted to preliminary lemmas about finite Cartesian powers of K.A characteristic subgroup of a group G is a subgroup which is mapped onto itself by all automorphisms of G. G is characteristically simple if its only characteristic subgroups are itself and the identity subgroup. Each characteristic subgroup of a group is a union of orbits of the automorphism group of the group. If G is ℵ0-categorical, then as the automorphism group of G has only a finite number of orbits, G has only a finite number of characteristic subgroups.

LOGICAL ASPECTS OF CAYLEY-GRAPHS: THE MONOID CASE

2006 ◽  
Vol 16 (02) ◽  
pp. 307-340 ◽  
Author(s):  
DIETRICH KUSKE ◽  
MARKUS LOHREY
Keyword(s):  
Cayley Graph ◽  
Cayley Graphs ◽  
Order Theory ◽  
Second Order ◽  
Point Of View ◽  
Direct Products ◽  
Graph Products ◽  
Arbitrary Graph ◽  
First Order ◽  
First Order Theory

Cayley-graphs of monoids are investigated under a logical point of view. It is shown that the class of monoids, for which the Cayley-graph has a decidable monadic second-order theory, is closed under free products. This result is derived from a result of Walukiewicz, stating that the decidability of monadic second-order theories is preserved under tree-like unfoldings. Concerning first-order logic, it is shown that the class of monoids, for which the Cayley-graph has a decidable first-order theory, is closed under arbitrary graph products, which generalize both, free and direct products. For the proof of this result, tree-like unfoldings are generalized to so-called factorized unfoldings. It is shown that the decidability of the first-order theory of a structure is preserved by factorized unfoldings. Several additional results concerning factorized unfoldings are shown.

Theory of mind deficit in people with schizophrenia during remission

2002 ◽  
Vol 32 (6) ◽  
pp. 1125-1129 ◽  
Author(s):  
R. HEROLD ◽  
T. TÉNYI ◽  
K. LÉNÁRD ◽  
M. TRIXLER
Keyword(s):  
Theory Of Mind ◽  
Acute Phase ◽  
Matched Control ◽  
Order Theory ◽  
The Other ◽  
First Order ◽  
First Order Theory ◽  
Significant Impairment ◽  
Schizophrenic Patients ◽  
Mind Task

Background. The authors' goal was to investigate the presence or absence of theory of mind impairments among people with schizophrenia during remission. Recent research results interpret theory of mind deficits as state rather than trait characteristics, connecting these impairments mainly to the acute episode of psychosis.Methods. Twenty patients with schizophrenia in remission and 20 matched control subjects were evaluated. Participants were presented with one first-order theory of mind task, one second-order theory of mind task, two metaphor and two irony tasks adapted from previous studies.Results. The schizophrenic patients performed a statistically significant impairment in the irony task, as there were no significant differences in the cases of the other evaluated tasks.Conclusions. These preliminary results suggest that theory of mind impairments can be detected not only in the acute phase as found in previous research studies, but also in remission.

The incompleteness theorems

2004 ◽  
Author(s):  
Shawn Hedman
Keyword(s):  
Mathematical Reasoning ◽  
Order Theory ◽  
Point Of View ◽  
Incompleteness Theorem ◽  
Bertrand Russell ◽  
First Order ◽  
First Order Theory ◽  
Incompleteness Theorems ◽  
Special Case ◽  
Gödel’S Incompleteness Theorems

In this chapter we prove that the structure N = (ℕ|+, · , 1) has a first-order theory that is undecidable. This is a special case of Gödel’s First Incompleteness theorem. This theorem implies that any theory (not necessarily first-order) that describes elementary arithmetic on the natural numbers is necessarily undecidable. So there is no algorithm to determine whether or not a given sentence is true in the structure N. As we shall show, the existence of such an algorithm leads to a contradiction. Gödel’s Second Incompleteness theorem states that any decidable theory (not necessarily first-order) that can express elementary arithmetic cannot prove its own consistency. We shall make this idea precise and discuss the Second Incompleteness theorem in Section 8.5. Gödel’s First Incompleteness theorem is proved in Section 8.3. Although they are purely mathematical results, Gödel’s Incompleteness theorems have had undeniable philosophical implications. Gödel’s theorems dispelled commonly held misconceptions regarding the nature of mathematics. A century ago, some of the most prominent mathematicians and logicians viewed mathematics as a branch of logic instead of the other way around. It was thought that mathematics could be completely formalized. It was believed that mathematical reasoning could, at least in principle, be mechanized. Alfred North Whitehead and Bertrand Russell envisioned a single system that could be used to derive and enumerate all mathematical truths. In their three-volume Principia Mathematica, Russell and Whitehead rigorously define a system and use it to derive numerous known statements of mathematics. Gödel’s theorems imply that any such system is doomed to be incomplete. If the system is consistent (which cannot be proved within the system by Gödel’s Second theorem), then there necessarily exist true statements formulated within the system that the system cannot prove (by Gödel’s First theorem). This explains why the name “incompleteness” is attributed to these theorems and why the title of Gödel’s 1931 paper translates (from the original German) to “On Formally Undecidable Propositions of Principia Mathematica and Related Systems” (translated versions appear in both [13] and [14]). Depending on one’s point of view, it may or may not be surprising that there is no algorithm to determine whether or not a given sentence is true in N.

Prime models and almost decidability

1986 ◽  
Vol 51 (2) ◽  
pp. 412-420 ◽  
Author(s):  
Terrence Millar
Keyword(s):  
Order Theory ◽  
The Other ◽  
Prime Model ◽  
First Order ◽  
Decidable Theory ◽  
Complete Extension ◽  
First Order Theory ◽  
Additional Constant ◽  
Open Question ◽  
Countable Models

This paper introduces and investigates a notion that approximates decidability with respect to countable structures. The paper demonstrates that there exists a decidable first order theory with a prime model that is not almost decidable. On the other hand it is proved that if a decidable complete first order theory has only countably many complete types, then it has a prime model that is almost decidable. It is not true that every decidable complete theory with only countably many complete types has a decidable prime model. It is not known whether a complete decidable theory with only countably many countable models up to isomorphism must have a decidable prime model. In [1] a weaker result was proven—if every complete extension, in finitely many additional constant symbols, of a theory T fails to have a decidable prime model, then T has 2ω nonisomorphic countable models. The corresponding statement for saturated models is false, even if all the complete types are recursive, as was shown in [2]. This paper investigates a variation of the open question via a different notion of effectiveness—almost decidable.A tree Tr will be a subset of ω<ω that is closed under predecessor. For elements f, g in ω<ω ∪ ωω, ƒ ⊲ g iffdf ∀i < lh(ƒ)[ƒ(i) = g(i)].

scholarly journals Note About a New Evaluation of the Direct Perturbations of the Planets on the Moon’s Motion

1981 ◽  
Vol 63 ◽  
pp. 265-266
Author(s):  
D. Standaert
Keyword(s):  
Order Theory ◽  
Second Order ◽  
Point Of View ◽  
Internal Point ◽  
First Order ◽  
Keplerian Orbits ◽  
First Order Theory ◽  
External Point ◽  
Constants Of Motion ◽  
The Mean

The aim of this paper is to present the principal features of a new evaluation of the direct perturbations of the planets on the Moon’s motion. Using the method already published in Celestial Mechanics (Standaert, 1980), we compute “a first-order theory” aiming at an accuracy of the order of the meter for all periodic terms of period less than 3 500 years.From an external point of view, we mean by that: a)keplerian orbits for the planets,b)the ELP-2000 solution of the Main Problem proposed by Mrs. Chapront (Chapront-Touzë, 1980),c)the first-order derivatives with respect to the constants of motion of the SALE theory of Henrard (Henrard, 1979).On the other hand, from an internal point of view, the computations include: d)the development in Legendre polynomials not only to the first-order in (a/a'), but also the following ones (up to the sixth-order for Venus, for example),e)the contributions of the second-order in the Lie triangle,f)second-order contributions coming from the corrections of the mean motions due to the planetary action.

A complicated ω-stable depth 2 theory

2011 ◽  
Vol 76 (1) ◽  
pp. 47-65 ◽  
Author(s):  
Martin Koerwien
Keyword(s):  
Order Theory ◽  
The Other ◽  
First Order ◽  
First Order Theory ◽  
Other Hand ◽  
Countable Models

AbstractWe present a countable complete first order theory T which is model theoretically very well behaved: it eliminates quantifiers, is ω-stable, it has NDOP and is shallow of depth two. On the other hand, there is no countable bound on the Scott heights of its countable models, which implies that the isomorphism relation for countable models is not Borel.

Locally finite theories

1986 ◽  
Vol 51 (1) ◽  
pp. 59-62 ◽  
Author(s):  
Jan Mycielski
Keyword(s):  
Main Idea ◽  
Order Theory ◽  
Interpolation Theorem ◽  
Point Of View ◽  
Finite Model ◽  
Consistent Theory ◽  
Locally Finite ◽  
First Order ◽  
First Order Theory ◽  
Finite Theory

We say that a first order theoryTislocally finiteif every finite part ofThas a finite model. It is the purpose of this paper to construct in a uniform way for any consistent theoryTa locally finite theory FIN(T) which is syntactically (in a sense) isomorphic toT.Our construction draws upon the main idea of Paris and Harrington [6] (I have been influenced by some unpublished notes of Silver [7] on this subject) and generalizes the syntactic aspect of their result from arithmetic to arbitrary theories. (Our proof is syntactic, and it is simpler than the proofs of [5], [6] and [7]. This reminds me of the simple syntactic proofs of several variants of the Craig-Lyndon interpolation theorem, which seem more natural than the semantic proofs.)The first mathematically strong locally finite theory, called FIN, was defined in [1] (see also [2]). Now we get much stronger ones, e.g. FIN(ZF).From a physicalistic point of view the theorems of ZF and their FIN(ZF)-counterparts may have the same meaning. Therefore FIN(ZF) is a solution of Hilbert's second problem. It eliminates ideal (infinite) objects from the proofs of properties of concrete (finite) objects.In [4] we will demonstrate that one can develop a direct finitistic intuition that FIN(ZF) is locally finite. We will also prove a variant of Gödel's second incompleteness theorem for the theory FIN and for all its primitively recursively axiomatizable consistent extensions.The results of this paper were announced in [3].

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