Editing Differential operator (section)

== Variants ==
===A differential operator of infinite order ===
A differential operator of infinite order is (roughly) a differential operator whose total symbol is a [[power series]] instead of a polynomial.

=== Bidifferential operator ===
A differential operator acting on two functions <math>D(g,f)</math> is called a '''bidifferential operator'''. The notion appears, for instance, in an associative algebra structure on a deformation quantization of a Poisson algebra.<ref>{{cite journal |last1=Omori |first1=Hideki |last2=Maeda |first2=Y. |last3=Yoshioka |first3=A. |title=Deformation quantization of Poisson algebras |journal=Proceedings of the Japan Academy, Series A, Mathematical Sciences |date=1992 |volume=68 |issue=5 |doi=10.3792/PJAA.68.97 |s2cid=119540529 |language=en|doi-access=free }}</ref>

=== Microdifferential operator ===
A [[microdifferential operator]] is a type of operator on an open subset of a cotangent bundle, as opposed to an open subset of a manifold. It is obtained by extending the notion of a differential operator to the cotangent bundle.<ref>{{harvnb|Schapira|1985|loc=§ 1.2. § 1.3.}}</ref>