Abstract Differential Algebra and the Analytic Case. II
A. Seidenberg · Proceedings of the American Mathematical Society · 1969
A. seidenberg Let R he the rational number-field, K = R(ux, • • • , um) a finite ordinary differential extension-field of R. Let u^*-*ca under an arbitrary abstract-field isomorphism a of K onto a field Kx.Let the field of formal power-series Pi(( 3)) be converted into a differential field by placing (Ha^z'/jl)' =HajZ'"1/(j-l)\.Then the assignment uf^Ui = 1iCijZ'lj\ defines a differential-field isomorphism of K onto R(u\, • ■ ■ , «m).