Name: Diffeomorphism-invariant averaging in quantum gravity and cosmology
Author: Anthony W. H. Preston

Diffeomorphism-invariant averaging in quantum gravity and cosmology

The thesis opens a new line of attack on quantum gravity — a renormalization-group flow for gravity that never fixes a gauge and works with or without a background metric — and shows that in modified gravity, averaging over small-scale ripples (backreaction) can produce an effect with the signature of a cosmological constant, i.e. it can mimic dark energy.

— In our words · Source: Diffeomorphism-invariant averaging in quantum gravity and cosmology (Anthony W. H. Preston)

[Use when]

Before inventing a new substance to explain an observation, check whether the math you already have produces it when you average over the scales you can't see.

[Why it matters]

It connects the two hardest problems in physics — quantum gravity and dark energy — through one mechanism: if small-scale gravitational ripples average out to look like a cosmological constant, dark energy might be an artifact of averaging, not a new substance.

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