English

Chow's theorem for Hilbert Grassmannians as a Wigner-type theorem

Mathematical Physics 2023-08-22 v2 math.MP

Abstract

Let HH be an infinite-dimensional complex Hilbert space. Denote by G(H){\mathcal G}_{\infty}(H) the Grassmannian formed by closed subspaces of HH whose dimension and codimension both are infinite. We say that X,YG(H)X,Y\in {\mathcal G}_{\infty}(H) are {\it ortho-adjacent} if they are compatible and XYX\cap Y is a hyperplane in both X,YX,Y. A subset CG(H){\mathcal C}\subset {\mathcal G}_{\infty}(H) is called an AA-{\it component} if for any X,YCX,Y\in {\mathcal C} the intersection XYX\cap Y is of the same finite codimension in both X,YX,Y and C{\mathcal C} is maximal with respect to this property. Let ff be a bijective transformation of G(H){\mathcal G}_{\infty}(H) preserving the ortho-adjacency relation in both directions. We show that the restriction of ff to every AA-component of G(H){\mathcal G}_{\infty}(H) is induced by a unitary or anti-unitary operator or it is the composition of the orthocomplementary map and a map induced by a unitary or anti-unitary operator. Note that the restrictions of ff to distinct components can be related to different operators.

Keywords

Cite

@article{arxiv.2302.01077,
  title  = {Chow's theorem for Hilbert Grassmannians as a Wigner-type theorem},
  author = {Mark Pankov and Adam Tyc},
  journal= {arXiv preprint arXiv:2302.01077},
  year   = {2023}
}
R2 v1 2026-06-28T08:30:15.588Z