Spectral Dimension of the Universe
J. Ambjorn (NBI Copenhagen, U. Utrecht), J. Jurkiewicz (U. Krakow),, R. Loll (U. Utrecht)

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.
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