Phase space analysis and cosmography of a two-fluid cosmological model

Abstract

In the framework of spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) space-time, we investigate a two-fluid cosmological model where a tachyon scalar field with self-interacting potential and a modified chaplygin gas with non-linear equation of state are taken as the background fluids. We perform phase space analysis of the autonomous system obtained from the cosmological governing equations by a suitable transformation of variables. Linear stability theory is employed to characterise the stability criteria for hyperbolic critical points. Numerical investigation is carried out for non-hyperbolic points. Our study reveals that modified chaplygin fluid dominated solutions cannot provide the late-time evolution. Late-time accelerated evolution is obtained only when the solution is dominated by tachyon fluid. This study also yields a late-time scaling attractor providing similar order of energy densities in its evolution. The adiabatic sound speed is evaluated for both the fluids and test the stability of the models independently. Further, we perform cosmographic analysis in the model independent way by evaluating all the cosmographic parameters and then $Om$ diagnostic is also found to compare our model with $\Lambda$CDM model.

22 pages, 12 captioned figures, accepted for publication in Physica Scripta

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