fσ8 as a Probe of Future-Singularity Dark Energy Models and ΛCDM

We investigate a class of dark energy models that lead to future cosmological singularities and confront them with observations of the growth of cosmic structure. Using the full linear perturbation formalism, we compute the redshift-space distortion observable f σ8(z) and fit the models to a compilation of growth-rate data. Treating all scenarios on the same footing, we perform parameter estimation and compare the overall quality of the fits obtained for the singularity models and for the concordance ΛCDM cosmology. Our results show which regions of parameter space remain compatible with present growth data and how these models perform relative to ΛCDM, providing a systematic assessment of the viability of future–singularity dark energy scenarios in light of structure formation measurements.