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In model theory, a discipline within mathematical logic, a non-standard model is a model of a theory that is not isomorphic to the intended model (or standard model).

Existence

If the intended model is infinite and the language is first-order, then the Löwenheim–Skolem theorems guarantee the existence of non-standard models. The non-standard models can be chosen as elementary extensions or elementary substructures of the intended model.

Importance

Non-standard models are studied in set theory, non-standard analysis and non-standard models of arithmetic.

See also

• Interpretation (logic)

References

1. Roman Kossak, 2004 Nonstandard Models of Arithmetic and Set Theory American Mathematical Soc.

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