Alternate Characterizations
If ƒ is an infinitely differentiable function defined on an open set D ⊂ R, then the following conditions are equivalent.
- 1) ƒ is real analytic.
- 2) There is a complex analytic extension of ƒ to an open set G ⊂ C which contains D.
- 3) For every compact set K ⊂ D there exists a constant C such that for every x ∈ K and every non-negative integer k the following bound holds:
The real analyticity of a function ƒ at a given point x can be characterized using the FBI transform.
Complex analytic functions are exactly equivalent to holomorphic functions, and are thus much more easily characterized.
Read more about this topic: Analytic Function
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