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exhaustion function (Definition)
Definition 1   Let $ G \subset {\mathbb{C}}^n$ be a domain and let $ f \colon G \to {\mathbb{R}}$ is called an exhaustion function whenever
$\displaystyle \{ z \in G \mid f(z) < r \}$    

is relatively compact in $ G$ for all $ r \in {\mathbb{R}}$.

For example $ G$ is pseudoconvex if and only if $ G$ has a continuous plurisubharmonic exhaustion function.

We can also define a bounded version.

Definition 2   Let $ G \subset {\mathbb{C}}^n$ be a domain and let $ f \colon G \to (-\infty,c]$ for some $ c \in {\mathbb{R}}$, is called a bounded exhaustion function whenever
$\displaystyle \{ z \in G \mid f(z) < r \}$    

is relatively compact in $ G$ for all $ r < c$.

A domain which has a bounded plurisubharmonic exhaustion function is usually referred to as a hyperconvex domain. Note that not all pseudoconvex domains have a bounded plurisubharmonic exhaustion function. For example the Hartogs's triangle does not, though it does have an unbounded one.

Bibliography

1
Steven G. Krantz. Function Theory of Several Complex Variables, AMS Chelsea Publishing, Providence, Rhode Island, 1992.



"exhaustion function" is owned by jirka.
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See Also: pseudoconvex

Also defines:  bounded exhaustion function, hyperconvex
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Cross-references: unbounded, Hartogs' triangle, bounded, plurisubharmonic, continuous, pseudoconvex, relatively compact, domain
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This is version 2 of exhaustion function, born on 2004-08-09, modified 2005-03-07.
Object id is 6092, canonical name is ExhaustionFunction.
Accessed 3352 times total.

Classification:
AMS MSC32T35 (Several complex variables and analytic spaces :: Pseudoconvex domains :: Exhaustion functions)
 32U10 (Several complex variables and analytic spaces :: Pluripotential theory :: Plurisubharmonic exhaustion functions)

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