What We Can Learn from the Running of the Spectral Index if no Tensors
  are Detected in the Cosmic Microwave Background Anisotropy
  In this paper we operate under the assumption that no tensors from inflation
will be measured in the future by the dedicated experiments and argue that,
while for single-field slow-roll models of inflation the running of the
spectral index will be hard to be detected, in multi-field models the running
can be large due to its strong correlation with non-Gaussianity. A detection of
the running might therefore be related to the presence of more than one active
scalar degree of freedom during inflation.
