Spectral Dimension of the Universe

TL;DR

This paper investigates the spectral dimension of quantum universes, revealing a transition from four dimensions at large scales to two dimensions at the Planck scale, suggesting a self-renormalizing quantum gravity mechanism.

Contribution

It provides evidence for dynamical dimensional reduction in quantum gravity through nonperturbative causal triangulated geometries.

Findings

Quantum universe is four-dimensional at large scales.

At short distances, the universe appears two-dimensional.

Supports the idea of self-renormalizing quantum gravity at the Planck scale.

Abstract

We measure the spectral dimension of universes emerging from nonperturbative quantum gravity, defined through state sums of causal triangulated geometries. While four-dimensional on large scales, the quantum universe appears two-dimensional at short distances. We conclude that quantum gravity may be "self-renormalizing" at the Planck scale, by virtue of a mechanism of dynamical dimensional reduction.