Late-Time Constraints on Future Singularity Dark Energy Models from Geometry and Growth

We confront two future-singularity dark-energy templates—sudden future singularities (SFSs) and finite scale factor singularities (FSFSs)—with late-time geometric probes and redshift-space distortion growth data. We compute the observable growth fσ8(z) by solving the full linear perturbation system (including the standard fiducial cosmology rescaling of RSD measurements) and build a joint χ2 from Pantheon+SH0ES SNe Ia, H(z), DESI AP-only BAO, and fσ8. Parameter constraints are obtained via grid-based profiling over nuisance parameters and the singularity time location parameter. We compare the viability and goodness of fit of the singularity scenarios to the ΛCDM reference.