Causally neutral quantum physics

TL;DR

This paper introduces an algebraic framework for quantum physics that handles both finite and infinite-dimensional systems, including quantum fields, in scenarios where spacetime causal structure is fundamentally uncertain, enabling new studies of quantum superpositions of spacetimes.

Contribution

It presents a novel algebraic approach to quantum causal structures that extends previous finite-dimensional studies to include quantum fields and infinite-dimensional systems.

Findings

Framework accommodates quantum fields in superpositions of spacetimes

Enables analysis of Lagrangian quantum field theories without definite causal structure

Bridges finite- and infinite-dimensional quantum causal models

Abstract

In fundamental theories that accounts for quantum gravitational effects, the spacetime causal structure is expected to be quantum uncertain. Previous studies of quantum causal structure focused on finite-dimensional systems. Here we present an algebraic framework that incorporates both finite- and infinite-dimensional systems including quantum fields. Thanks to the absence of a definite spacetime causal structure, Lagrangian quantum field theories can be studied on a quantum superposition of spacetimes with a point identification structure.