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Complete Local Reflexivity

An operator space $ X$ is called completely locally reflexive [EJR98, §1], if to each finite dimensional subspace there is $ L \subset X ^{**}$ a net of completely contractive mappings $ \varphi_\alpha : L\rightarrow X$ that converges to the embedding $ L \rightarrow X^{*
*}$ in the point weak$ ^*$ topology.53

This property is inherited by arbitrary subspaces. In general it is not preserved by quotients. In the case that for example the kernel is an M-ideal (e.g. the twosided ideal of a $ C^*$-algebra) and that the original space is completely reflexive we have that the quotient space is completely locally reflexive [ER94, Thm. 4.6].

Banach spaces are always locally reflexive (Principle of local reflexivity [Sch70]).

On the contrary, not all operator spaces are completely locally reflexive. For example the full $ C^*$-algebra of the free group on two generators $ C^*(F_2)$ and $ B(\ell_2)$ are not completely locally reflexive [EH85, p. 124-125].

An operator space $ X$ is completely locally reflexive, if and only if one (and then every) of the following conditions is satisfied for all finite dimensional operator spaces $ L$ [EJR98, §1, 4.4, 5.8]:

  1. $ L\stackrel{\scriptscriptstyle \vee}{\otimes}X^{**}\stackrel{\mathrm{cb}}{=}(L\stackrel{\scriptscriptstyle \vee}{\otimes}X)^{**}$, where $ \stackrel{\scriptscriptstyle \vee}{\otimes}$ denotes the injective operator space tensor product,
  2. $ \mathit{CB}(L^*,X^{**})\stackrel{\mathrm{cb}}{=}\mathit{CB}(L^*,X)^{**}$,
  3. $ L^*\stackrel{\scriptscriptstyle \wedge}{\otimes}X^*\stackrel{\mathrm{cb}}{=}(L\stackrel{\scriptscriptstyle \vee}{\otimes}X)^*$, where $ \stackrel{\scriptscriptstyle \wedge}{\otimes}$ denotes the projective operator space tensor product and $ \stackrel{\scriptscriptstyle \vee}{\otimes}$ denotes the injective operator space tensor product,
  4. $ \mathit{CN}(X,L^*)\stackrel{\mathrm{cb}}{=}\mathit{CI}(X,L^*)$, where $ \mathit{CN}(\cdot,\cdot)$ denotes the completely nuclear and $ \mathit{CI}(\cdot,\cdot)$ the completely integral mappings,
  5. $ \iota(\varphi)=\iota(\varphi^*)$ for all $ \varphi\in CI(X,L^*)$.
In the conditions 1), 2) and 3) it suffices to check the usual isometry to prove the complete isometry.



Footnotes

... topology.53
The difference to the definition of local reflexivity is the fact that the $ \varphi_\alpha$ are not only supposed to be contractive, but even completely contractive.


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Prof. Gerd Wittstock 2001-01-07