Constraints on the Universe as a Numerical Simulation

TL;DR

This paper explores the hypothesis that our universe is a numerical simulation on a lattice, analyzing observable consequences such as cosmic ray spectra and fundamental constants to set bounds on the simulation's lattice spacing.

Contribution

It provides the first detailed analysis of how a universe simulated on a lattice could produce observable effects, setting bounds on the lattice spacing from cosmic ray data.

Findings

Inverse lattice spacing >~ 10^11 GeV from cosmic ray spectrum

Potential lattice effects in cosmic ray angular distributions

Constraints on simulation parameters from high-energy physics observations

Abstract

Observable consequences of the hypothesis that the observed universe is a numerical simulation performed on a cubic space-time lattice or grid are explored. The simulation scenario is first motivated by extrapolating current trends in computational resource requirements for lattice QCD into the future. Using the historical development of lattice gauge theory technology as a guide, we assume that our universe is an early numerical simulation with unimproved Wilson fermion discretization and investigate potentially-observable consequences. Among the observables that are considered are the muon g-2 and the current differences between determinations of alpha, but the most stringent bound on the inverse lattice spacing of the universe, b^(-1) >~ 10^(11) GeV, is derived from the high-energy cut off of the cosmic ray spectrum. The numerical simulation scenario could reveal itself in the distributions of the highest energy cosmic rays exhibiting a degree of rotational symmetry breaking that reflects the structure of the underlying lattice.