Confronting dark energy models mimicking $\Lambda$CDM epoch with   observational constraints: future cosmological perturbations decay or future   Rip?
  We confront dark energy models which are currently similar to $\Lambda$CDM theory with observational data which include the SNe data, matter density perturbations and baryon acoustic oscillations data. DE cosmology under consideration may evolve to Big Rip, type II or type III future singularity, or to Little Rip or Pseudo-Rip universe. It is shown that matter perturbations data define more precisely the possible deviation from $\Lambda$CDM model than consideration of SNe data only. The combined data analysis proves that DE models under consideration are as consistent as $\Lambda$CDM model. We demonstrate that growth of matter density perturbations may occur at sufficiently small background density but still before the possible disintegration of bound objects (like clusters of galaxies, galaxies, etc) in Big Rip, type III singularity, Little Rip or Pseudo-Rip universe. This new effect may bring the future universe to chaotic state well before disintegration or Rip. 
Artyom V. Astashenok and Sergei D. Odintsov
gr-qc astro-ph.CO