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Feb 14, 2016 at 5:56 comment added ABB Everting that I know about: We have always $1-$supp$\phi$=supp$N_{\tilde{\phi}}$ where supp$N_{\tilde{\phi}}$ is the supremum of all positive elements in the unit ball of $N_{\tilde{\phi}}$. Since $\phi$ is a pure state then its support is a minimal projection, say $e$ and so $N_{\tilde{\phi}}=A^{**}(1-e)$ is a maximal $w^*$-closed left ideal in $A^{**}$. It seems that $N_{\phi}=A^{**}(1-e)\cap A$ (which is a maximal closed left ideal in $A$). So the question is : If $e$ is a minimal projection in $A^{**}$ then $$A^{**}(1-e)=\overline{A^{**}(1-e)\cap A}^{w^*}$$
Feb 13, 2016 at 12:38 comment added Simon Henry I hav'nt been able to find a satisfying answer, but I have the impression that the situation is very different depending on if in the GNS representation associated to $\phi$ there is or not operator in the image of $A$ (so roughly on whether if algebra is type I/post-liminal or not). My guess would be that it is true for type I/post-liminal algebras and not necessarily for more general algebra... Have you tried to consider non type I examples ?
S Feb 13, 2016 at 11:33 history suggested Chris Ramsey CC BY-SA 3.0
Added tags and cleaned up presentation.
Feb 13, 2016 at 11:19 review Suggested edits
S Feb 13, 2016 at 11:33
Feb 13, 2016 at 9:34 comment added Simon Henry In commutative algebra it also holds for finite linear combination of characters I think. In $K(H)$ if you take some injective trace class operator it produces a state $\phi$ such that $N_{\overline{\phi}} = 0$ and hence statisfies your property without being pure or finite combination of pure states.
Feb 13, 2016 at 5:53 history asked ABB CC BY-SA 3.0