Quantum gravity states, entanglement graphs and second-quantized tensor networks

TL;DR

This paper establishes a connection between tensor network states and group field theory in quantum gravity, showing how spacetime structure emerges from entanglement patterns among quanta of space.

Contribution

It introduces a second-quantized tensor network framework for quantum gravity states and explores their relation to group field theory and discrete spacetime structures.

Findings

Discrete spatial manifolds arise from entanglement patterns.

Graph label independence reflects diffeomorphism invariance.

Relational setting allows effective distinguishability of space quanta.

Abstract

In recent years, the import of quantum information techniques in quantum gravity opened new perspectives in the study of the microscopic structure of spacetime. We contribute to such a program by establishing a precise correspondence between the quantum information formalism of tensor networks (TN), in the case of projected entangled-pair states (PEPS) generalised to a second-quantized framework, and group field theory (GFT) states, and by showing how, in this quantum gravity approach, discrete spatial manifolds arise as entanglement patterns among quanta of space, having a dual representation in terms of graphs and simplicial complexes. We devote special attention to the implementation and consequences of the label independence of the graphs/networks, corresponding to the indistinguishability of the space quanta and representing a discrete counterpart of the diffeomorphism invariance of a consistent quantum gravity formalism. We also outline a relational setting to recover distinguishability of graph/network vertices at an effective and physical level, in a partial semi-classical limit of the theory.