# Perturbative Algebraic Quantum Field Theory on Quantum Spacetime: Adiabatic and Ultraviolet Convergence

## TL;DR

This paper develops a perturbative algebraic quantum field theory framework on quantum spacetime, achieving ultraviolet finiteness and removing the adiabatic cutoff issue by replacing point fields with quantum point fields, while noting Lorentz invariance breaking.

## Contribution

It introduces a novel approach replacing point fields with quantum point fields to address adiabatic cutoff removal in quantum spacetime perturbation theory.

## Key findings

- Ultraviolet finite perturbation expansion achieved.
- Adiabatic cutoff becomes irrelevant in equilibrium states.
- Interacting vacuum state obtained in zero-temperature limit.

## Abstract

The quantum structure of Spacetime at the Planck scale suggests the use, in defining interactions between fields, of the Quantum Wick product. The resulting theory is ultraviolet finite, but subject to an adiabatic cutoff in time which seems difficult to remove. We solve this problem here by another strategy: the fields at a point in the interaction Lagrangian are replaced by the fields at a quantum point, described by an optimally localized state on QST; the resulting Lagrangian density agrees with the previous one after spacetime integration, but gives rise to a different interaction hamiltonian. But now the methods of perturbative Algebraic Quantum Field Theory can be applied, and produce an ultraviolet finite perturbation expansion of the interacting observables. If the obtained theory is tested in an equilibrium state at finite temperature the adiabatic cutoff in time becomes immaterial, namely it has no effect on the correlation function at any order in perturbation theory. Moreover, the interacting vacuum state can be obtained in the vanishing temperature limit. It is nevertheless important to stress that the use of states which are optimally localized for a given observer brakes Lorentz invariance at the very beginning.