$C^\ast$-categorical prefactorization algebras for superselection sectors and topological order
Marco Benini, Victor Carmona, Pieter Naaijkens, Alexander Schenkel
May 12, 2025
This paper presents a conceptual and efficient geometric framework to encode
the algebraic structures on the category of superselection sectors of an
algebraic quantum field theory on the $n$-dimensional lattice $\mathbb{Z}^n$.
It is shown that, under certain assumptions which are implied by Haag duality,
the monoidal $C^\ast$-categories of localized superselection sectors carry the
structure of a locally constant prefactorization algebra over the category of
cone-shaped subsets of $\mathbb{Z}^n$. Employing techniques from higher
algebra, one extracts from this datum an underlying locally constant
prefactorization algebra defined on open disks in the cylinder
$\mathbb{R}^1\times\mathbb{S}^{n-1}$. While the sphere $\mathbb{S}^{n-1}$
arises geometrically as the angular coordinates of cones, the origin of the
line $\mathbb{R}^1$ is analytic and rooted in Haag duality. The usual braided
(for $n=2$) or symmetric (for $n\geq 3$) monoidal $C^\ast$-categories of
superselection sectors are recovered by removing a point of the sphere
$\mathbb{R}^1\times(\mathbb{S}^{n-1}\setminus\mathrm{pt}) \cong\mathbb{R}^n$
and using the equivalence between $\mathbb{E}_n$-algebras and locally constant
prefactorization algebras defined on open disks in $\mathbb{R}^n$. The
non-trivial homotopy groups of spheres induce additional algebraic structures
on these $\mathbb{E}_n$-monoidal $C^\ast$-categories, which in the case of
$\mathbb{Z}^2$ is given by a braided monoidal self-equivalence arising
geometrically as a kind of `holonomy' around the circle $\mathbb{S}^1$. The
locally constant prefactorization algebra structures discovered in this work
generalize, under some mild geometric conditions, to other discrete spaces and
thereby provide a clear link between the geometry of the localization regions
and the algebraic structures on the category of superselection sectors.
Keywords:
prefactorization algebras, C*-categories, higher algebra, algebraic quantum field theory, Superselection sectors, topological order