# Superreal number

In abstract algebra, the **superreal numbers** are a class of extensions of the real numbers, introduced by H. Garth Dales and W. Hugh Woodin as a generalization of the hyperreal numbers and primarily of interest in non-standard analysis, model theory, and the study of Banach algebras. The field of superreals is itself a subfield of the surreal numbers.

Dales and Woodin's superreals are distinct from the super-real numbers of David O. Tall, which are lexicographically ordered fractions of formal power series over the reals.[1]

## Formal definition

Suppose X is a Tychonoff space, also called a T_{3½} space, and C(X) is the algebra of continuous real-valued functions on X. Suppose P is a prime ideal in C(X). Then the factor algebra A = C(X)/P is by definition an integral domain which is a real algebra and which can be seen to be totally ordered. The field of fractions F of A is a **superreal field** if F strictly contains the real numbers , so that F is not order isomorphic to .

If the prime ideal P is a maximal ideal, then F is a field of hyperreal numbers (Robinson's hyperreals being a very special case).

## References

- Tall, David (March 1980), "Looking at graphs through infinitesimal microscopes, windows and telescopes" (PDF),
*Mathematical Gazette*,**64**(427): 22–49, CiteSeerX 10.1.1.377.4224, doi:10.2307/3615886, JSTOR 3615886

## Bibliography

- Dales, H. Garth; Woodin, W. Hugh (1996),
*Super-real fields*, London Mathematical Society Monographs. New Series,**14**, The Clarendon Press Oxford University Press, ISBN 978-0-19-853991-9, MR 1420859 - Gillman, L.; Jerison, M. (1960),
*Rings of Continuous Functions*, Van Nostrand, ISBN 978-0442026912