We propose the locally pumped dark energy (LPDE) mechanism in which cosmic acceleration is triggered by the emergence of nonlinear 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 localized, 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 $\mathrm{\Lambda }\mathrm{CDM}$ 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 realization 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).

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• Cosmological constant
• Cosmological parameters
• Cosmology
• Dark energy
• Large scale structure of the Universe