Vector Field and Inflation
  We have investigated if the vector field can give rise to an accelerating
phase in the early universe. We consider a timelike vector field with a general
quadratic kinetic term in order to preserve an isotropic background spacetime.
The vector field potential is required to satisfy the three minimal conditions
for successful inflation: i) $\rho>0$, ii) $\rho+3P < 0$ and iii) the slow-roll
conditions. As an example, we consider the massive vector potential and small
field type potential as like in scalar driven inflation.
