English

Quadratic & additive mappings on operator commuting elements in JBW*-algebras

Operator Algebras 2026-03-18 v1 Functional Analysis

Abstract

Let A\mathfrak{A} and B\mathfrak{B} be JBW^*-algebras whose sets of unitaries are denoted by U(A)\mathcal{U}(\mathfrak{A}) and U(B)\mathcal{U}(\mathfrak{B}), respectively. We show that U(A)\mathcal{U}(\mathfrak{A}) is closed for Jordan products of operator commuting pairs inside itself. Assuming that A\mathfrak{A} and B\mathfrak{B} are JBW^*-algebras without direct summands of type I1I_1 or I2I_2, we prove that for each bicontinuous bijection Φ:U(A)U(B)\Phi : \mathcal{U}(\mathfrak{A}) \rightarrow \mathcal{U}(\mathfrak{B}) satisfying Φ(uv)=Φ(u)Φ(v),\Phi (u \circ v) = \Phi (u)\circ \Phi (v), whenever uu and vv are operator commuting unitaries in A\mathfrak{A}, there exist a linear Jordan ^*-isomorphism θ:AB\theta: \mathfrak{A} \rightarrow \mathfrak{B}, a real linear mapping β:AsaZ(Bsa)\beta: \mathfrak{A_{sa}}\rightarrow Z(\mathfrak{B}_{sa}), and an invertible central element cBsac \in \mathfrak{B}_{sa} such that Φ(eia)=eiβ(a)eicθ(a)=eiβ(a)θ(eiθ1(c)a), \Phi(e^{i a}) = e^{i \beta (a)}\circ e^{i c\circ\theta(a)} = e^{i \beta(a)} \circ \theta \left( e^{i \theta^{-1}( c )\circ a}\right), for all aAsaa\in \mathfrak{A}_{sa}. The conclusion improves when A\mathfrak{A} is a JBW^*-algebra factor not of type I2I_2.

Keywords

Cite

@article{arxiv.2603.16687,
  title  = {Quadratic & additive mappings on operator commuting elements in JBW*-algebras},
  author = {Gerardo M. Escolano and Jan Hamhalter and Antonio M. Peralta and Armando R. Villena},
  journal= {arXiv preprint arXiv:2603.16687},
  year   = {2026}
}
R2 v1 2026-07-01T11:24:27.440Z