Deviation from the Cosmological Constant or Systematic Errors?

Understand

Motivated by the fact that both SNe Ia and GRBs seem to prefer a dark energy EOS greater than -1 at redshifts $z \gtrsim 0.5$, we perform a careful investigation on this situation.

• We find that the deviation of dark energy from the cosmological constant at redshifts $z \gtrsim 0.5$ is large enough that we should pay close attention to it with future observational data.
• Such a deviation may arise from some biasing systematic errors in the handling of SNe Ia and/or GRBs or more interestingly from the nature of the dark energy itself.