Resolving primordial physics through correlated signatures
  We discuss correlations among spectral observables as a new tool for differentiating between models for the primordial perturbation. We show that if generated in the isocurvature sector, a running of the scalar spectral index is correlated with the statistical properties of non-Gaussianities. In particular, we find a large running will inevitably be accompanied by a large running of $f_{\rm NL}$ and enhanced $g_{\rm NL}$, with $g_{\rm NL}\gg f_{\rm NL}^2$. If the tensor to scalar ratio is large, a large negative running must turn positive on smaller scales. Interestingly, the characteristic scale of the transition could potentially distinguish between the inflaton and isocurvature fields. 
Kari Enqvist, David J. Mulryne and Sami Nurmi
astro-ph.CO