English

Operator maps of Jensen-type

Functional Analysis 2021-07-23 v2 Operator Algebras

Abstract

Let BJ(H)\mathbb{B}_J(\mathcal H) denote the set of self-adjoint operators acting on a Hilbert space H\mathcal{H} with spectra contained in an open interval JJ. A map Φ ⁣:BJ(H)B(H)sa\Phi\colon\mathbb{B}_J(\mathcal H)\to {\mathbb B}(\mathcal H)_\text{sa} is said to be of Jensen-type if Φ(CAC+DBD)CΦ(A)C+DΦ(B)D \Phi(C^*AC+D^*BD)\le C^*\Phi(A)C+D^*\Phi(B)D for all A,BBJ(H) A, B \in B_J(\mathcal H) and bounded linear operators C,D C,D acting on H \mathcal H with CC+DD=I C^*C+D^*D=I, where II denotes the identity operator. We show that a Jensen-type map on a infinite dimensional Hilbert space is of the form Φ(A)=f(A)\Phi(A)=f(A) for some operator convex function f f defined in J J .

Keywords

Cite

@article{arxiv.1708.07028,
  title  = {Operator maps of Jensen-type},
  author = {Frank Hansen and Mohammad Sal Moslehian and Hamed Najafi},
  journal= {arXiv preprint arXiv:1708.07028},
  year   = {2021}
}

Comments

8 pages

R2 v1 2026-06-22T21:21:48.935Z