$H(z)$ diagnostics on the nature of dark energy
  The two dominant components of the cosmic budget today, pressureles matter and dark energy, may or may not be interacting with each other. Currently, both possibilities appear compatible with observational data. We propose several criteria based on the history of the Hubble factor that can help discern whether they are interacting and whether dark energy is phantom or quintessence in nature. 
Sergio del Campo, Ramon Herrera and Diego Pavon
astro-ph.CO gr-qc hep-ph hep-th