Dynamical systems analysis of tachyon-dark-energy models from a new perspective

In this work, we present a new scheme to study the tachyon-dark-energy model using dynamical systems analysis by considering parametrization of the equation of state (EOS) of the dark energy. Both the canonical and phantom field dynamics are investigated. In our method, we do not require any explicit form of the tachyon potential. Instead of the potential, we start with an approximate form of the EOS of the tachyon field. This EOS is phenomenologically motivated and contains some dimensionless parameters. Using our method, we can construct the dynamical system which gives rise to the time evolution of the Universe. We have considered two different parametrizations of the EOS and studied the phase space dynamics in detail. Our analysis shows Taylor series parametrization of the EOS has serious cosmological limitations. We have also provided an example of how this method can be applied to coupled tachyon models with a specific form of interaction. Our proposal is generic in nature and can be applied to other scalar field dark energy models.

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