Novel Proposal of the Cosmological Constant: Dark Energy, Dark Matter, and the Accelerated Expansion of the Universe

Abstract

Recent observations from the James Webb Space Telescope (JWST) have intensified the long-standing tension in measurements of the Hubble constant and have raised questions about the completeness of the standard cosmological-constant description of dark energy. The ΛCDM model successfully accounts for a wide range of large-scale observations by combining ordinary matter, radiation, cold dark matter, and a cosmological constant Λ. Nevertheless, the physical origin of Λ remains unsettled: the observed magnitude of the vacuum energy density is many orders of magnitude smaller than naïve quantum-field estimates. This paper examines the conceptual relationships among cosmological distance, recession velocity, dark matter, dark energy, and the cosmological constant. We emphasize that dark matter and dark energy play distinct dynamical roles—dark matter contributes gravitationally to structure formation and early deceleration, while dark energy drives the late-time acceleration of cosmic expansion. We introduce a phenomenological density-ratio parameter L ≡ ρ_DE / ρ_DM as a flexible diagnostic of the relative importance of the two dark components. Building on this ratio, we propose a revised expansion relation that recovers the conventional low-redshift Hubble law while allowing a density-dependent modification at larger distances. Any such alternative must ultimately be tested against the established observational constraints provided by Type I supernovae, baryon acoustic oscillations, the cosmic microwave background, and large-scale structure surveys.