Abstract
Let R be a domain and D a sequence of derivations of R with length ≥2. Let be the subring consisting of those q in the symmetric Martindale quotient ring of R such that qI ∪ Iq ⊆ R for a nonzero D-invariant ideal I of R. It is shown here that the symmetric Martindale quotient ring of the Ore extension R[X, D] is the Ore extension . Our proof depends on an interesting combinatoric result on words.
Notes
Communicated by A. Smoktunowicz.