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C*-extreme implies linear extreme for UCP on arbitrary Hilbert spaces

Determine whether, for arbitrary Hilbert spaces H and unital C*-algebras A, every C*-extreme point of the C*-convex set UCP(A,B(H)) is a linear extreme point of UCP(A,B(H)).

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Background

Proposition 2.4 shows that when H is finite-dimensional, C*-extreme points of UCP(A,B(H)) are linear extreme points. The authors explicitly state that it is unknown whether this inclusion continues to hold when H is an arbitrary Hilbert space, highlighting a gap between finite- and infinite-dimensional settings.

References

It is unknown whether statement (i) holds true when H is an arbitrary Hilbert space.

$C^*$-extreme contractive completely positive maps (2412.05008 - R et al., 6 Dec 2024) in After Proposition 2.4, Section 2