The Evolution of Universe with th B-I Type Phantom Scalar Field

Abstract

We considered the phantom cosmology with a lagrangian $\displaystyle L=\frac{1}{\eta}[1-\sqrt{1+\eta g^{\mu\nu}\phi_{, \mu}\phi_{, \nu}}]-u(\phi)$, which is original from the nonlinear Born-Infeld type scalar field with the lagrangian $\displaystyle L=\frac{1}{\eta}[1-\sqrt{1-\eta g^{\mu\nu}\phi_{, \mu}\phi_{, \nu}}]-u(\phi)$. This cosmological model can explain the accelerated expansion of the universe with the equation of state parameter $w\leq-1$. We get a sufficient condition for a arbitrary potential to admit a late time attractor solution: the value of potential $u(X_c)$ at the critical point $(X_c,0)$ should be maximum and large than zero. We study a specific potential with the form of $u(\phi)=V_0(1+\frac{\phi}{\phi_0})e^{(-\frac{\phi}{\phi_0})}$ via phase plane analysis and compute the cosmological evolution by numerical analysis in detail. The result shows that the phantom field survive till today (to account for the observed late time accelerated expansion) without interfering with the nucleosynthesis of the standard model(the density parameter $\Omega_{\phi}\simeq10^{-12}$ at the equipartition epoch), and also avoid the future collapse of the universe.