The Cosmological Constant as a Present Effective Dark-Sector Value: A Compact Phenomenological Parametrization for Cosmic Acceleration That Need Not Be Eternal

This work proposes a compact phenomenological model in which the cosmological constant is treated as a present effective value that may evolve over cosmic time. The model remains close to the standard cosmological framework at recent epochs while allowing the dark component to decay in the distant future, potentially avoiding eternal cosmic acceleration. It is intended as a minimal effective parametrization that can be tested against cosmological observations.