| | Ultraproduct -- Facts, Info, and Encyclopedia article (Site not responding. Last check: 2007-10-22) |
 | | Certainly the most important case is the construction of the (Click link for more info and facts about hyperreal numbers) hyperreal numbers by taking the ultraproduct of countably infinitely many copies of the field of (Any rational or irrational number) real numbers. |
 | | The (Click link for more info and facts about hyperreal numbers) hyperreal numbers are the ultraproduct of one copy of the (Any rational or irrational number) real numbers for every natural number, with regard to an ultrafilter containing all cofinite sets of natural numbers. |
 | | Analogously, you could define (Click link for more info and facts about nonstandard complex numbers) nonstandard complex numbers by taking the ultraproduct of copies of the field of (A number of the form a+bi where a and b are real numbers and i is the square root of -1) complex numbers. |
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