Chaos-protected locality

TL;DR

This paper explores a novel type of speed limit in complex systems where simple signals are constrained by an approximate speed limit, despite the rapid spread of information and entanglement, suggesting chaos can coexist with locality.

Contribution

It introduces the concept of chaos-protected locality, showing how simple signals can obey speed limits even when complex information spreads rapidly, reconciling non-local interactions with local spacetime geometry.

Findings

Simple signals obey approximate speed limits.

Complex information can spread rapidly despite locality.

Chaotic interactions can preserve spacetime locality.

Abstract

Microscopic speed limits that constrain the motion of matter, energy, and information abound in physics, from the "ultimate" speed limit set by light to Lieb-Robinson speed limits in quantum spin systems. In addition to these state-independent speed limits, systems can also be governed by emergent state-dependent speed limits indicating slow dynamics arising, for example, from slow low-energy quasiparticles. Here we describe a different kind of speed limit: a situation where complex information/entanglement spreads rapidly, in a fashion inconsistent with any speed limit, but where simple signals continue to obey an approximate speed limit. If we take the point of view that the motion of simple signals defines the local spacetime geometry of the universe, then the effects we describe show that spacetime locality can be compatible with a high degree of non-local interactions provided these are sufficiently chaotic. With this perspective, we sharpen a puzzle about black holes recently raised by Shor and propose a schematic resolution.