Phantom without ghost

Understand

The Nine-Year WMAP results combined with other cosmological data seem to indicate an enhanced favor for the phantom regime, comparing to previous analyses.

• This behavior, unless reversed by future observational data, suggests to consider the phantom regime more thoroughly.
• In this work we provide three modified gravitational scenarios in which we obtain the phantom realization without the appearance of ghosts degrees of freedom, which plague the naive approaches on the subject, namely the Brans-Dicke type gravity, the scalar-Einstein-Gauss-Bonnet gravity, and the $F(R)$ gravity, which are moreover free of perturbative instabilities.
• The phantom regime seems to favor the gravitational modification instead of the universe-content alteration.