Scalar-Cost Dark Energy: Linking Cosmic Expansion to Energetic Structure Growth

Abstract Introducing a new framework for cosmic acceleration: the Scalar-Cost Dark Energy model (SCDE). Unlike a cosmological constant, dark energy arises from an energetic cost tied to spacetime expansion. Represented by an additional scalar-field kinetic term, this cost remains negligible at high redshift but activates dynamically at late times. The model preserves the Lambda CDM background while producing distinct, testable perturbative signatures: approximately 5% enhancement in linear growth rate, 3–5% increase in weak-lensing shear power on intermediate scales, a 4% rise in cluster abundance above 10^14 solar masses, and a 0.02 upward shift in S_8, alleviating—but not removing—the weak-lensing vs. CMB tension. It is stable (no ghosts, sound speed squared > 0), consistent with early-universe constraints, and falsifiable with upcoming large-scale structure data.