What is dimensional reduction really telling us?

TL;DR

This paper provides numerical evidence that dimensional reduction in quantum gravity models implies a variable speed of light, challenging traditional notions of constant light speed and suggesting a need to rethink our understanding of time.

Contribution

It demonstrates a link between dimensional reduction and variable light speed in CDT quantum gravity, highlighting implications for the nature of time.

Findings

Numerical evidence of variable speed of light in CDT

Dimensional reduction correlates with superluminal effects

Reconsideration of time's role in quantum gravity theories

Abstract

Numerous approaches to quantum gravity report a reduction in the number of spacetime dimensions at the Planck scale. However, accepting the reality of dimensional reduction also means accepting its consequences, including a variable speed of light. We provide numerical evidence for a variable speed of light in the causal dynamical triangulation (CDT) approach to quantum gravity, showing that it closely matches the superluminality implied by dimensional reduction. We argue that reconciling the appearance of dimensional reduction with a constant speed of light may require modifying our understanding of time, an idea originally proposed in Ref. 1.