41 research outputs found
Cosmology with exponential potentials
We examine in the context of general relativity the dynamics of a spatially
flat Robertson-Walker universe filled with a classical minimally coupled scalar
field \phi of exponential potential ~ e^{-\mu\phi} plus pressureless baryonic
matter. This system is reduced to a first-order ordinary differential equation,
providing direct evidence on the acceleration/deceleration properties of the
system. As a consequence, for positive potentials, passage into acceleration
not at late times is generically a feature of the system, even when the
late-times attractors are decelerating. Furthermore, the structure formation
bound, together with the constraints on the present values of \Omega_{m},
w_{\phi} provide, independently of initial conditions and other parameters,
necessary conditions on \mu. Special solutions are found to possess intervals
of acceleration. For the almost cosmological constant case w_{\phi} ~ -1, as
well as, for the generic late-times evolution, the general relation
\Omega_{\phi}(w_{\phi}) is obtained.Comment: RevTex4, 9 pages, 2 figures, References adde