English

Bures--Kuratowski metrics and simplicial complexes for completely bounded maps

Operator Algebras 2026-04-07 v1 Algebraic Topology Functional Analysis Metric Geometry

Abstract

Let AA be a unital CC^*-algebra and HH a Hilbert space. The cone \CP(A,B(H))\CP(A,B(H)) of completely positive maps carries the Bures metric β\beta, closely related to the cb-norm. We introduce a family of Bures--Kuratowski (BK) metrics on \CB(A,B(H))\CB(A,B(H)) that extend β\beta exactly on \CP(A,B(H))\CP(A,B(H)). The construction combines a Kuratowski embedding of the Bures cone, based at an anchor θ\CP(A,B(H))\theta\in\CP(A,B(H)), with a regular-representation Hausdorff coordinate arising from universal regular models. Each BK metric admits an p\ell^p-wedge decomposition, splitting \CB(A,B(H))\CB(A,B(H)) into the Bures cone and a non-CP component attached at θ\theta. We then study Vietoris--Rips and \v{C}ech complexes of BK metric spaces. The wedge formula yields explicit criteria for mixed simplices, a join-type description of the mixed Rips complex, and ball-intersection criteria for mixed \v{C}ech simplices. For finite point clouds, this makes the mixed simplicial geometry computable from the two component metrics and reveals new homological features arising from the interaction between the CP and non-CP sectors.

Cite

@article{arxiv.2604.04248,
  title  = {Bures--Kuratowski metrics and simplicial complexes for completely bounded maps},
  author = {Remus Floricel and Sarah Plosker and Avner Sadikov},
  journal= {arXiv preprint arXiv:2604.04248},
  year   = {2026}
}

Comments

4 figures

R2 v1 2026-07-01T11:54:40.723Z