Solving the Cosmic Coincidence Problem: The Locally Pumped Dark Energy Model

TL;DR

This paper introduces the Locally Pumped Dark Energy (LPDE) model, linking cosmic acceleration to structure formation through a scalar field affected by dark matter halos, providing a novel explanation for the coincidence problem.

Contribution

The paper proposes a new mechanism where dark energy arises from local scalar field shifts induced by non-linear dark matter structures, connecting structure formation with cosmic acceleration.

Findings

Vacuum-energy domination occurs at redshift ~1.

The model naturally explains the timing of cosmic acceleration.

It aligns well with recent cosmological data, including DESI.

Abstract

We propose the Locally Pumped Dark Energy (LPDE) mechanism in which cosmic acceleration is triggered by the emergence of non-linear dark matter structure. In an effective-field-theory description, coarse-graining over the density contrast profile, whose short-wavelength modes grow during halo formation, induces a shift in the local equilibrium point of a second, sufficiently heavy scalar field $\chi$. At early times, the pump mechanism is negligible and $\chi$ remains fixed at the origin, contributing no DE. As structures form, the equilibrium value of $\chi$ is locally displaced within halos, generating a vacuum energy whose global contribution, in a mean-field picture, is controlled by the halo volume filling factor. If the $\chi$ field is sufficiently heavy, with a Compton wavelength limited by halo scales, its response is localised, and spatial gradients are exponentially suppressed on large scales. After volume-averaging over the halo population, the resulting contribution on large scales behaves as a homogeneous DE component. Using the halo mass function of a fiducial $\Lambda$CDM cosmology, we show that vacuum-energy domination generically emerges at $z\sim\mathcal{O}(1)$, naturally correlating cosmic acceleration with structure formation. For reference, we present an explicit realisation of such a mechanism and show that, by naturally featuring a transient acceleration epoch, it can be in excellent agreement with the most recent cosmological data, including the Dark Energy Spectroscopic Instrument (DESI).