A quantum Bose-Hubbard model with evolving graph as toy model for emergent spacetime

TL;DR

This paper introduces a quantum spin system model where the interaction graph evolves dynamically, serving as a toy model for emergent spacetime and exploring quantum gravity concepts through entanglement and causal structure.

Contribution

It proposes a novel quantum Hubbard model with a dynamically evolving interaction graph, linking matter and geometry without predefined spatial properties.

Findings

Demonstrates entanglement between matter and spatial degrees of freedom.

Shows the dynamical evolution of the interaction graph influences local and causal structures.

Analyzes asymptotic behavior and analogues of gravitational phenomena in the model.

Abstract

We present a toy model for interacting matter and geometry that explores quantum dynamics in a spin system as a precursor to a quantum theory of gravity. The model has no a priori geometric properties, instead, locality is inferred from the more fundamental notion of interaction between the matter degrees of freedom. The interaction terms are themselves quantum degrees of freedom so that the structure of interactions and hence the resulting local and causal structures are dynamical. The system is a Hubbard model where the graph of the interactions is a set of quantum evolving variables. We show entanglement between spatial and matter degrees of freedom. We study numerically the quantum system and analyze its entanglement dynamics. We analyze the asymptotic behavior of the classical model. Finally, we discuss analogues of trapped surfaces and gravitational attraction in this simple model.