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Difference between revisions of "Standard Borel space"

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(Created page with "''Also: standard measurable space'' {{MSC|28A05|03E15,54H05}} $ \newcommand{\R}{\mathbb R} \newcommand{\C}{\mathbb C} \newcommand{\Om}{\Omega} \newcommand{\A}{\mathcal A} \newc...")
 
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'''Theorem.''' All uncountable standard Borel spaces are mutually isomorphic.
 
'''Theorem.''' All uncountable standard Borel spaces are mutually isomorphic.
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<table><TR><TD valign="top">[3]</TD> <TD valign="top">Alexander S. Kechris, "Classical descriptive set theory", Springer-Verlag (1995) | {{MR|1321597}} | {{ZBL|0819.04002}}</TD></TR>
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<TR><TD valign="top">[5]</TD> <TD valign="top">Richard M. Dudley, "Real analysis and probability", Wadsworth&Brooks/Cole (1989) | {{MR|0982264}} | {{ZBL|0686.60001}}</TD></TR>
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[[Category:Classical measure theory]]

Revision as of 20:04, 27 December 2011

Also: standard measurable space

2020 Mathematics Subject Classification: Primary: 28A05 Secondary: 03E1554H05 [MSN][ZBL]

$ \newcommand{\R}{\mathbb R} \newcommand{\C}{\mathbb C} \newcommand{\Om}{\Omega} \newcommand{\A}{\mathcal A} \newcommand{\B}{\mathcal B} \newcommand{\P}{\mathbf P} $ A measurable space $(X,\A)$ is called standard if it satisfies the following equivalent conditions:

  • $(X,\A)$ is isomorphic to some compact metric space with the Borel σ-algebra;
  • $(X,\A)$ is isomorphic to some separable complete metric space with the Borel σ-algebra;
  • $(X,\A)$ is isomorphic to some Borel subset of some separable complete metric space with the Borel σ-algebra.

Finite and countable standard Borel spaces are trivial: all subsets are measurable. Two such spaces are isomorphic if and only if they have the same cardinality, which is trivial. But the following result is surprising and highly nontrivial.

Theorem. All uncountable standard Borel spaces are mutually isomorphic.

References

[3] Alexander S. Kechris, "Classical descriptive set theory", Springer-Verlag (1995) | MR1321597 | Zbl 0819.04002
[5] Richard M. Dudley, "Real analysis and probability", Wadsworth&Brooks/Cole (1989) | MR0982264 | Zbl 0686.60001
How to Cite This Entry:
Standard Borel space. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Standard_Borel_space&oldid=19969