# Equation of state parameter $\gamma($P=$\gamma\rho$ )in Brans-dicke parameter

I have used an emperical relation of scalar field $$\phi=\phi_0(\frac{a}{a_0})^n$$ where n is $$\frac{-G \ddot}{GH}$$ from recent studied n is found negative and present value of $$\gamma$$ lies between -0.6 and -0.67 which is sufficient for accelerated expansion. Taking this into account I have chosen 3 values of n and plot for $$\gamma$$ vs t and found the time for which there is transition from +ve pressure to -ve pressure and start up time of accelerated expansion. But for the positive $$\gamma$$ if we take into account at very early epoch $$\gamma=1/3$$ and then followed by $$\gamma=0$$ and then negative and less than -0.3 to accelerated expansion. But here initially the gamma increases with time ,but $$\gamma$$ has to decrease with time from 1/3 to 0 and then -ve??