Instability of scalar perturbations in a phantomic cosmological scenarioJ. C. Fabris1, D. F. Jardim2 and S. V. B. Gonçalves2
1 Institut d'Astrophysique de Paris - 98bis, Boulevard Arago, 75014 Paris, France, EU
2 Departamento de Física, Universidade Federal do Espírito Santo - 29060-900, Vitória, Espírito Santo, Brazil
received 3 December 2007; accepted in final form 24 April 2008; published June 2008
published online 4 June 2008
Scalar perturbations can grow during a phantomic cosmological phase as the big rip is approached, in spite of the highly accelerated expansion regime, if the equation of state is such that = w < - . It is shown that such result is independent of the spatial curvature. The perturbed equations are exactly solved for any value of the curvature parameter k and of the equation of state parameter w. Growing modes are found asymptotically under the condition . Since the Hubble radius decreases in a phantom universe, such result indicates that a phantom scenario may not survive longtime due to gravitational instability.
98.80.-k - Cosmology.
95.36.+x - Dark energy.
© EPLA 2008