Recent many physicists suggest that the dark energy in the universe might
result from the Born-Infeld(B-I) type scalar field of string theory. The
universe of B-I type scalar field with potential can undergo a phase of
accelerating expansion. The corresponding equation of state parameter lies in
the range of −1<ω<−1/3. The equation of state parameter
of B-I type scalar field without potential lies in the range of
0≤ω≤1. We find that weak energy condition and strong energy
condition are violated for phantom B-I type scalar field. The equation of state
parameter lies in the range of ω<−1.Comment: 10 pages without figure