Co-existence of alternative Generalized Chaplygin Gas and other Dark Energies in the Framework of Fractal Universe

We have explored the possibility of the co-existence of two forms of dark energy in the form of an alternative Generalized Chaplygin Gas (GCG) along with a scalar field of field theoretic or extra dimensional origin in the background of a fractal universe. The essential physical model parameters have been computed and their variations have been plotted. Fractal cosmology in an universe dominated by the alternative GCG (overcoming the drawbacks of the conventional form of GCG) has also been studied by computing the equation of state, deceleration and statefinder parameters. Their variations with the redshift have also been studied. We have tried to construct alternative cosmological models deviating from standard cosmology that can be put to observational testing.

💡 Research Summary

The paper investigates a cosmological scenario in which an alternative form of the Generalized Chaplygin Gas (GCG) coexists with various scalar‑field dark‑energy components within a fractal universe (FU) framework. The authors begin by motivating fractal cosmology: large‑scale galaxy surveys reveal voids and structures that challenge the strict homogeneity assumed in the standard cosmological principle. In a fractal universe the space‑time measure is modified to μ(t)∝t^{β‑1}, where β encodes a scale‑dependent effective dimension that approaches the usual four at late times but can be smaller in the early, UV‑dominated epoch. This non‑trivial measure leads to modified Friedmann equations in which the effective energy density and pressure acquire additional terms proportional to (β‑1)H/t.

The conventional GCG, defined by p = –A/ρ^{α}, suffers from a high sound speed and oscillatory features in the matter power spectrum, rendering it incompatible with current CMB, BAO and weak‑lensing data. To overcome these drawbacks the authors introduce an “alternative GCG” with an extended equation of state \