|
|
| (One intermediate revision by one other user not shown) |
| Line 1: |
Line 1: |
| In [[mathematics]], and in particular [[model theory]], a '''prime model''' is a [[model (abstract)|model]] which is as simple as possible. Specifically, a model <math>P</math> is prime if it admits an [[elementary embedding]] into any model <math>M</math> to which it is [[elementarily equivalent]] (that is, into any model <math>M</math> satisfying the same [[complete theory]] as <math>P</math>).
| | They contact me Emilia. I am a meter reader but I strategy on changing it. To collect cash is 1 of the issues I adore most. North Dakota is where me and my spouse reside.<br><br>Also visit my web site :: [http://Url.Fbcdurant.org/dietmealdelivery74619 http://Url.Fbcdurant.org] |
| | |
| == Cardinality ==
| |
| | |
| In contrast with the notion of [[saturated model]], prime models are restricted to very specific [[cardinality|cardinalities]] by the [[Löwenheim-Skolem theorem]]. If <math>L</math> is a [[first-order language]] with cardinality <math>\kappa</math> and <math>T</math> a complete theory over <math>L,</math> then this theorem guarantees a model for <math>T</math> of cardinality <math>\max(\kappa,\aleph_0);</math> therefore no prime model of <math>T</math> can have larger cardinality since at the very least it must be elementarily embedded in such a model. This still leaves much ambiguity in the actual cardinality. In the case of countable languages, all prime models are at most countable.
| |
| | |
| == Relationship with saturated models ==
| |
| | |
| There is a duality between the definitions of prime and saturated models. Half of this duality is discussed in the article on [[saturated model]]s, while the other half is as follows. While a saturated model realizes as many [[type (model theory)|type]]s as possible, a prime model realizes as few as possible: it is an [[atomic model (mathematical logic)|atomic model]], realizing only the types which cannot be [[omitting types theorem|omitted]] and omitting the remainder. This may be interpreted in the sense that a prime model admits "no frills": any characteristic of a model which is optional is ignored in it.
| |
| | |
| For example, the model <math>\langle {\mathbb N}, S\rangle</math> is a prime model of the theory of the natural numbers ''N'' with a successor operation ''S''; a non-prime model might be <math>\langle {\mathbb N} + {\mathbb Z}, S\rangle ,</math> meaning that there is a ''copy'' of the full integers which lies disjoint from the original copy of the natural numbers within this model; in this add-on, arithmetic works as usual. These models are elementarily equivalent; their theory admits the following axiomatization (verbally):
| |
| # There is a unique element which is not the successor of any element;
| |
| # No two distinct elements have the same successor;
| |
| # No element satisfies ''S''<sup>''n''</sup>(''x'') = ''x'' with ''n''>0.
| |
| These are, in fact, two of [[Peano's axioms]], while the third follows from the first by induction (another of Peano's axioms). Any model of this theory consists of disjoint copies of the full integers in addition to the natural numbers, since once one generates a submodel from 0 all remaining points admit both predecessors and successors indefinitely. This is the outline of a proof that <math>\langle {\mathbb N}, S\rangle</math> is a prime model.
| |
| | |
| ==References==
| |
| *{{Citation | last1=Chang | first1=Chen Chung | last2=Keisler | first2=H. Jerome | author2-link=Howard Jerome Keisler | title=Model Theory | origyear=1973 | publisher=Elsevier | edition=3rd | series=Studies in Logic and the Foundations of Mathematics | isbn=978-0-444-88054-3 | year=1990}}
| |
| | |
| [[Category:Model theory]]
| |
They contact me Emilia. I am a meter reader but I strategy on changing it. To collect cash is 1 of the issues I adore most. North Dakota is where me and my spouse reside.
Also visit my web site :: http://Url.Fbcdurant.org