Relative locality in a quantum spacetime and the pregeometry of $\kappa$-Minkowski

TL;DR

This paper introduces a new Hilbert space-based framework for $$-Minkowski quantum spacetime, revealing how quantum fuzziness leads to a relativity of locality, with implications for understanding quantum geometry.

Contribution

It presents a pregeometric Hilbert space representation of $$-Minkowski spacetime, differential calculus, and symmetry generators, clarifying quantum spacetime fuzziness and relative locality.

Findings

Quantum spacetime fuzziness depends on observer-inferred distances.

Relativity of locality manifests as distance-dependent event properties.

The framework unifies operators, calculus, and symmetries in a single Hilbert space.

Abstract

We develop a new description of the much-studied $\kappa$-Minkowski noncommutative spacetime, centered on representing on a single Hilbert space not only the $\kappa$-Minkowski coordinates, but also the associated differential calculus and the $\kappa$-Poincar\'e symmetry generators. In this "pregeometric" representation the relevant operators act on the kinematical Hilbert space of the covariant formulation of quantum mechanics, which we argue is the natural framework for studying the implications of the step from commuting spacetime coordinates to the $\kappa$-Minkowski case, where the spatial coordinates do not commute with the time coordinate. The empowerment provided by this kinematical-Hilbert space representation allows us to give a crisp characterization of the "fuzziness" of $\kappa$-Minkowski spacetime, whose most striking aspect is a relativity of spacetime locality. We show that relative locality, which had been previously formulated exclusively in classical-spacetime setups, for a quantum spacetime takes the shape of a dependence of the fuzziness of a spacetime point on the distance at which an observer infers properties of the event that marks the point.