Stability of Singularity-free Cosmological Solutions in Ho\v{r}ava-Lifshitz Gravity

Understand

We study stability of singularity-free cosmological solutions with positive cosmological constant based on projectable Ho\v{r}ava-Lifshitz (HL) theory.

• In HL theory, the isotropic and homogeneous cosmological solutions with bounce can be realized if spacial curvature is non-zero.
• By performing perturbation analysis around non-flat Friedmann-Lemaitre-Robertson-Walker (FLRW) spacetime, we derive a quadratic action and discuss the stability, i.e, ghost and tachyon-free conditions.
• Although the squared effective mass of scalar perturbation must be negative in infrared regime, we can avoid tachyon instability by considering strong Hubble friction.