# Operator-algebraic construction of gauge theories and Jones' actions of Thompson's groups

## TL;DR

This paper constructs 1+1-dimensional gauge theories on a spacetime cylinder using operator algebras, Jones' actions of Thompson's groups, and heat-kernel states, revealing new connections between quantum gauge theories and group actions.

## Contribution

It introduces a novel operator algebraic framework for gauge theories incorporating Thompson's groups and heat-kernel states, extending previous lattice and loop quantum gravity approaches.

## Key findings

- Constructed nets of C*-algebras for gauge theories on a torus.
- Established actions of Thompson's group T on these algebras.
- Derived hyperfinite type III factors with nontrivial time evolution.

## Abstract

Using ideas from Jones, lattice gauge theory and loop quantum gravity, we construct 1+1-dimensional gauge theories on a spacetime cylinder. Given a separable compact group $G$, we construct localized time-zero fields on the spatial torus as a net of C*-algebras together with an action of the gauge group that is an infinite product of $G$ over the dyadic rationals and, using a recent machinery of Jones, an action of Thompson's group $T$ as a replacement of the spatial diffeomorphism group. Adding a family of probability measures on the unitary dual of $G$ we construct a state and obtain a net of von Neumann algebras carrying a state-preserving gauge group action. For abelian $G$, we provide a very explicit description of our algebras. For a single measure on the dual of $G$, we have a state-preserving action of Thompson's group and semi-finite von Neumann algebras. For $G=\mathbf{S}$ the circle group together with a certain family of heat-kernel states providing the measures, we obtain hyperfinite type III factors with a normal faithful state providing a nontrivial time evolution via Tomita-Takesaki theory (KMS condition). In the latter case, we additionally have a non-singular action of the group of rotations with dyadic angles, as a subgroup of Thompson's group $T$, for geometrically motivated choices of families of heat-kernel states.