If Do, D1, … are linear maps from an algebra A to an algebra B, both over the complexes, then {Do, D1, …} is a system of derivations if for all a, b in A and for all nonnegative integers k, we have Where C(k, i) is the binomial coefficient k!/i! (k—i)!. By (1.1) we see that Do must be a homomorphism and in case Do = I, where I is the identity map, D1 is a derivation and, for k ≧ 2, the Dk are higher derivations in the sense of Jacobson (1964), page 191. Gulick (1970), Theorem 4.2, proved that if A is a commutative regular semi-simple F-algebra with identity and {DO, D1, …} is a system of derivations from A to B = C(S(A)), the algebra of all continuous functions on the spectrum of A, where Dox = x, then the Dk are all continuous. Carpenter (1971), Theorem 5, shows that the regularity condition is unnecessary and Loy (1973) generalizes this a bit further. One of the many interesting features of systems of derivations is that they help determine analytic structure in Banach algebras (see for example, Miller (to appear)).
Topological algebras of continuous functions over valued fields