Higher Dimensional Energetic Causal Sets

TL;DR

This paper extends the energetic causal set model to 2+1 dimensions, demonstrating a phase transition to a time-symmetric phase with crystal-like structures, advancing understanding of quantum gravity's foundational irreversibility.

Contribution

The authors successfully generalize the ECS model to higher dimensions, overcoming measure-zero solution challenges by introducing finite interaction cross-sections and stochasticity.

Findings

Observation of a phase transition to time-symmetry in 2+1 dimensions

Emergence of crystal-like structures in the causal set

Discrete dynamical systems behavior with limit cycles

Abstract

The energetic causal set (ECS) program of Cort\^es and Smolin, whose distinguishing feature is the foundational time irreversibility of the evolution equations of quantum gravity, was initiated ten years ago. The model showed the emergence of a time-reversible phase from the time-irreversible foundational regime, but originally only had one spatial dimension. The extension to two and more spatial dimensions has posed a substantial challenge, the higher-dimensional set of solutions having measure zero (requiring infinitely-specified initial conditions). This challenge is overcome here with the extension of the ECS to 2+1 dimensions, invoking a finite interaction cross-section to determine generation of new events and including an adjustable fundamental stochasticity. As in the 1+1 dimensional case, we successfully observe a phase transition into a time-symmetric phase, here through the emergence of crystal-like structures. Due to the irreversible evolution we also witness the discrete dynamical systems behaviour of the 1d+1 case explored in later articles of the ECS program, in which the model is captured in and out of the limit cycles which here take the form of lattice crystals. In a companion paper we carry out a detailed parameter investigation and study the causal network underlying the set, explaining the emergence of the time-symmetric phase. In a final section we propose a view of science as a (potential) unifier of threads, and present one such perspective unifying aspects of quantum gravity, biology, and artificial general intelligence (AGI).