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.

Formal definition

Suppose X is a Tychonoff space, also called a T space, and C is the algebra of continuous real-valued functions on X. Suppose P is a prime ideal in C. Then the factor algebra A = C/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.