Non-Gaussianity Consistency Relation for Multifield Inflation

While detection of the local form'' bispectrum of primordial perturbations would rule out all single-field inflation models, multifield models would still be allowed. We show that multifield models described by the delta N formalism obey an inequality between f(NL) and one of the local-form trispectrum amplitudes, tau(NL), such that tau(NL) > 1/2(6/5 f(NL))(2) with a possible logarithmic scale dependence, provided that 2-loop terms are small. Detection of a violation of this inequality would rule out most of multifield models, challenging inflation as a mechanism for generating the primoridal perturbations.