A classical theorem of Steinitz states that the characteristic of an algebraically closed fields, together with its absolute degree of transcendency, uniquely determine the field (up to isomorphism). It is easily seen that the word real-closed cannot be substituted for the words algebraically closed in this theorem. It is therefore natural to inquire what invariants other than the absolute transcendence degree are needed in order characterize a real-closed field.
© 1955 Princeton University, Department of Mathematics
Erdös, P.; Gillman, L.; Henriksen, M. An Isomorphism Theorem For Real-Closed Fields. Ann. of Math. (2) 61, (1955). 542–554.