Dark Energy Without Dark Energy: Emergent Cosmic Acceleration From BEC Dark Matter Sequestration

This paper introduces the Subtractive Cosmological Model (SCM). In this framework, cosmic acceleration doesn't need a new energy component. It appears as an observational consequence of dark matter being drawn out of the smooth cosmological background. Dark matter is modelled as a global Bose–Einstein condensate (BEC) superfluid with attractive self-interactions, which give it a negative quantum pressure. As structure forms, dark matter is progressively sequestered into bound haloes, which thins the background field. The field pressure that had been decelerating baryonic matter weakens, so the expansion appears to speed up. No new force pushes outward. The force that was pulling inward has simply diminished. No energy is created or transferred, and no new degrees of freedom are introduced. The field-pressure dark energy density is derived from first principles using the Gross–Pitaevskii equation and the Sheth–Tormen halo mass function. The paper shows that a physical BEC condensation threshold is needed to avoid catastrophic early dark energy. That threshold sets a mass–redshift relation for the dark matter boson, m ∝ (1 + z_c)^(3/5). The model is tested in a staged MCMC campaign against six independent datasets: - Planck 2018 CMB temperature and polarisation- DESI 2024 baryon acoustic oscillations- Pantheon+ Type Ia supernovae- eBOSS DR16 and BOSS DR12 redshift-space distortions- DES Year 1 cosmic shear- Planck PSZ2 galaxy cluster counts Key results: - The field-pressure fraction has an upper limit of ε < 0.0032 at 95% confidence. There is a suggestive but inconclusive 1.7σ preference for ε > 0.- The condensation redshift is z_c = 2.43 ± 0.38, which coincides with the epoch of peak cosmic star formation.- The implied BEC boson mass is 22.9 ± 1.6 meV/c² (under the CMB-temperature approximation). This would be within reach of next-generation axion-like particle experiments.- The growth rate is about 2% above ΛCDM at z ≈ 0.4–0.7, consistent with RSD data. The S₈ tension with DES Year 1 is reduced but not resolved.- Planck PSZ2 cluster counts drive ε → 0. This is reported openly as a genuine observational challenge for the mechanism at current precision. At current precision the data do not favour the SCM over ΛCDM, but the model remains physically distinct and makes concrete, testable predictions for DESI Year 5, CMB-S4, Euclid and SKA 21-cm tomography.