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 δN formalism obey an inequality between f_NL and one of the local-form trispectrum amplitudes, τ_NL, such that τ_NL>12(65f_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.