1. AVOIDING THE PHANTOM MENACE Júlio C. Fabris Departamento de Física – UFES Barcelona - 2006

2. Inflation requires: Strong energy condition is violated!

3. However, the null energy condition does not need to be violated:

4. A phantom field (or fluid) is characterized by All energy conditions are violated!

5. The phantom case became quite fashion due to the recent observational results Of course, the predictions depend on which data are taken into account and how the statistics is made Combining CMB (WMAP), matter clustering (SDSS e 2dFGRS) and supernovae: Matts Roos, astrop-ph/0509089

6. Other estimations: CMB, SNIa, large scale structures S. Nannestad e E. Mortsell, JCAP 0409, 001(2004) Including X-Rays S.W. Allen et al., Mon. Not. R. Astron. Soc. 353, 457(2004)

9. Inevitable consequence for a Universe dominated by an exotic fluid where all the energy conditions are violated: A “big rip”: a curvature singularity in a future finite proper time This requires, however, homogeneity and isotropy

10. Some remarks on the perturbative behaviour of the phantom fields Considering a barotropic equation of state The following equation governing the gravitational potential is found: J.C.F and S.V.B. Gonçalves, PRD, 2006

11. The scale factor behaves as The equation for the potential becomes

12. The solution depends on the sign of the pressure:

13. Asymptotic behaviour

15. The instability at small scale may be solved using a field representation:

16. The perturbed equation is Using the background solution,

17. The solution is:

18. Asymptotic behaviour:

29. The Hubble horizon is given by It grows for normal fields, but it decreases when the phanton field dominates the matter content of the universe

30. Considering now local configurations: An “anomalous” scalar field A “normal” scalar field K.A. Bronnikov e J.C.F, PRL(2006)

31. The horizon can be the border between regular regions A horizon A static region An expanding non-singular universe

32. Phantom inflation may be very attractive today And it may not be so dangerous! Moreover, local configurations are very attractive