Direct Constraints on Exponential Potential Quintessence: Forecast Evidence for Dynamical Dark Energy from Future Cosmological Surveys

We present a comprehensive forecast for the exponential potential quintessence model using simulated data from four future cosmological probes: full Planck 2018 cosmic microwave background (temperature, polarization, and lensing), DESI baryon acoustic oscillations, CSST 3×2pt weak lensing (cosmic shear, galaxy-galaxy lens- ing, and galaxy clustering), and LSST Type Ia supernovae. We employ both the Chevallier-Polarski-Linder (CPL) parameterization and a direct sampling of the po- tential slope parameter λ via a modified CLASS–MontePython pipeline. Under a fiducial model with λ = 0.5, we obtain w0 = −0.961 ± 0.011, wa = 0.081 ± 0.035, and λ = 0.506±0.219. The deviation from the cosmological constant value w0 = −1 is 3.5σ, and λ = 0 is excluded at the 2.3σ level. Our results demonstrate that next-generation surveys can provide significant evidence for dynamical dark energy if the true universe is described by an exponential potential with a coupling strength λ ∼ 0.5.