PlanetPhysics/Birkhoff Kakutani Theorem
Birkhoff-Kakutani theorem
edit\begin{theorem}
A topological group is metrizable if and only if is Hausdorff and the identity of has a countable neighborhood basis. Furthermore, if G is metrizable , then admits a compatible metric which is left-invariant, that is, a right-invariant metric also exists under these conditions. \end{theorem}
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editReferences
edit- ↑ Howard Becker, Alexander S. Kechris. 1996. The Descriptive Set Theory of Polish Group Actions. (London Mathematical Society Lecture Note Series) , Cambridge University Press: Cambridge, UK, p.14.