Exponential potentials and cosmological scaling solutions

Nov, 1997
6 pages
Published in:
  • Phys.Rev.D 57 (1998) 4686-4690
e-Print:
Report number:
  • SUSX-TH-97-022,
  • SUSSEX-AST-97-11-1,
  • PU-RCG-97-20

Citations per year

19972004201120182025020406080
Abstract: (arXiv)
We present a phase-plane analysis of cosmologies containing a barotropic fluid with equation of state pγ=(γ1)ργp_\gamma = (\gamma-1) \rho_\gamma, plus a scalar field ϕ\phi with an exponential potential Vexp(λκϕ)V \propto \exp(-\lambda \kappa \phi) where κ2=8πG\kappa^2 = 8\pi G. In addition to the well-known inflationary solutions for λ2<2\lambda^2 < 2, there exist scaling solutions when λ2>3γ\lambda^2 > 3\gamma in which the scalar field energy density tracks that of the barotropic fluid (which for example might be radiation or dust). We show that the scaling solutions are the unique late-time attractors whenever they exist. The fluid-dominated solutions, where V(ϕ)/ργ0V(\phi)/\rho_\gamma \to 0 at late times, are always unstable (except for the cosmological constant case γ=0\gamma = 0). The relative energy density of the fluid and scalar field depends on the steepness of the exponential potential, which is constrained by nucleosynthesis to λ2>20\lambda^2 > 20. We show that standard inflation models are unable to solve this `relic density' problem.
  • cosmological model
  • field theory: scalar
  • scaling
  • model: fluid
  • energy: density
  • potential
  • critical phenomena
  • inflation
  • numerical calculations