Characteristic functions and products of derivatives (Q809206)
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scientific article; zbMATH DE number 4210453
| Language | Label | Description | Also known as |
|---|---|---|---|
| English | Characteristic functions and products of derivatives |
scientific article; zbMATH DE number 4210453 |
Statements
Characteristic functions and products of derivatives (English)
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1991
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The following Theorem is proven: For a subset S of the reals R the following are mutually equivalent: (1) the characteristic function of S is a product of finitely many derivatives; (2) S is ambiguous and \(T=R\setminus S\) is porous; (3) there exist derivatives f and g such that \(f=g=1\) on S and \(fg=0\) on T.
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ambiguous set
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porous set
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characteristic function
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product of finitely many derivatives
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