Hasse derivative

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In mathematics, the Hasse derivative is a generalisation of the derivative which allows the formulation of Taylor's theorem in coordinate rings of algebraic varieties.

Contents

Definition

Let k[X] be a polynomial ring over a field k. The r-th Hasse derivative of Xn is

if nr and zero otherwise. [1] In characteristic zero we have

Properties

The Hasse derivative is a generalized derivation on k[X] and extends to a generalized derivation on the function field k(X), [1] satisfying an analogue of the product rule

and an analogue of the chain rule. [2] Note that the are not themselves derivations in general, but are closely related.

A form of Taylor's theorem holds for a function f defined in terms of a local parameter t on an algebraic variety: [3]

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References

  1. 1 2 Goldschmidt (2003) p.28
  2. Goldschmidt (2003) p.29
  3. Goldschmidt (2003) p.64